A555 -3.85 FD with an OBX

[83rampage]

Being the typical cheap TD member, the cost of an OBX vs. Quaife has me sold on the OBX. Problem is I am not really in love with the A520 hybrid idea, and basically being forced to a 3.50 final drive. I did look around for a 3.85 FD 520, but never did find one (Dodge Garage says they exist).

I got looking at the 555 carrier, and compared it to the 520 crown gear I had. Looked like if you cut the middle out of the 555 peice, you would have a suitable gear to bolt onto the OBX and eliminate the need to do a hybrid.

So I took the 555 crown gear assembly to a friend, who was able to machine the 3.85 crown gear to the same inner dimention as the 520 gear. The only real difference now is the "face" the gear that bolts to the OBX is about .010" deeper than a 520 gear, and the bolts are larger, so the OBX would need to be drilled to accomodate the bolts.

I figure that I would check the gear mesh of the pinion shaft to the crown gear on final assembly and if that .010 difference on the face made it so the gears were offset, I could shim the carrier assembly to get the gears to line up, although I doubt that .010" will be a problem.

So....has anyone actually done this before ( I realize the machine work is cost prohibitive to some, but it seems like there are members on here with free access to machining), and if not is there anything you tranny gurus can think I am missing?

My biggest concern with the concept was whether the 3.85 gear could be machined, and that has been done.

[135sohc]

I did look around for a 3.85 FD 520, but never did find one (Dodge Garage says they exist).


They do exist. Sort of the like the opposite when trying to find a 3.50 523 and only finding 3.85's/3.77's since the majority of A520's being dropped into P bodys and the like had the 3.50 final drive. The minivans and maybe the daytona/lebaron? would have the 3.85 final drive (heavier cars had it)

I do like the idea of your conversion though... The pitch of the 555 (and 568) ring/pinion teeth is less than that of the other transmissions so it is stronger without question and the bolts being M12 vs m10 is probably not as importent but still better IMO.

Would love to see pictures of the setup. probably a first for the community and as direct fit parts become harder to locate adapting other pieces to fit will become more common.

[Pat]

Very cool! I also would like to see any pix you could share.

[BadAssPerformance]

Sunscribed

[Juggy]

I would find yourself a 568 transmission

the 523 was readily available in 3.85fd in the n/a cars during 90-91. If one were to run a 568 they would just have to swap the 523 3.85 ring gear and pinion to keep the same gear ratio and use the OBX

[83rampage]

I would find yourself a 568 transmission

the 523 was readily available in 3.85fd in the n/a cars during 90-91. If one were to run a 568 they would just have to swap the 523 3.85 ring gear and pinion to keep the same gear ratio and use the OBX


Thanks for the input, but I decided quite a while ago to go with the 555. I have 4 555s collected over the past few years as spares sitting under the stairs in the garage (plus the one I'm working on), so I'm not changing course and going to the 568......not happening.

I will post up some pics soon once I pick up the ring gear today.

[tryingbe]

There isn't much of a "ring gear" since the differential is pretty much unbolt into halves.

http://www.thelostartof.net/tryingbe/dodge/Daytonaproject/LSD2.jpg


And block type LSD sucks. Stock is better than "upgrade" block LSD.
Less than 5000 miles.

http://www.thelostartof.net/tryingbe/dodge/blocklsd/1.jpg
http://www.thelostartof.net/tryingbe/dodge/blocklsd/2.jpg
http://www.thelostartof.net/tryingbe/dodge/blocklsd/3.jpg
http://www.thelostartof.net/tryingbe/dodge/blocklsd/4.jpg
http://www.thelostartof.net/tryingbe/dodge/blocklsd/5.jpg

[83rampage]

Ok got the ring gear back and it looks awesome. Got some pics but I'm either too tech inferior to be able to post them, or the site doesn't allow me to. I was hoping to get back the center section they cut out for some pictures also but it ended up destroyed and in the scrap bin. Edit-pics sent to 135sohc

Thanks Tryingbe for posting some pictures of what it looks like "before", as I never did get any of those.:(

[135sohc]

My connection is dragging right now for some reason so I'll upload the other pictures tomorrow if so desired.39031

[wallace]

Does this mod work to put a OBX in a 568 and retain the stock gearing?

[135sohc]

It should. differential assembly is the same between both transmissions.

[Tbird232ci]

I had a thought. Instead of drilling and tapping the OBX for the larger bolts, what about having some sleeves made to adapt the ring gear to the smaller bolts? I would rather ruin a ring gear, than ruin an OBX.

[83rampage]

The ring gear itself is threaded, so you would need to build a adapter that reduced the threads down to M10 from M12. Not sure that is even possible, but wouldn't trust a setup like that.

If you did drill the OBX larger, you could always use sleeves like you mentioned, so you really aren't ruining the OBX.

[Tbird232ci]

Thanks for that info. I thought the OBX was threaded, and not the ring gear.

[cordes]

I've thought about doing this before, but I assumed the machine work would be more expensive than building a hybrid myself. Keep us updated.

[GLHS60]

This is a great idea and it looks like it will work fine. I've been thinking of how to make a 3:50 final drive A 555 but keep the 4 pin diff. and now you got me thinking!!

Thanks
Randy




Being the typical cheap TD member, the cost of an OBX vs. Quaife has me sold on the OBX. Problem is I am not really in love with the A520 hybrid idea, and basically being forced to a 3.50 final drive. I did look around for a 3.85 FD 520, but never did find one (Dodge Garage says they exist).

I got looking at the 555 carrier, and compared it to the 520 crown gear I had. Looked like if you cut the middle out of the 555 peice, you would have a suitable gear to bolt onto the OBX and eliminate the need to do a hybrid.

So I took the 555 crown gear assembly to a friend, who was able to machine the 3.85 crown gear to the same inner dimention as the 520 gear. The only real difference now is the "face" the gear that bolts to the OBX is about .010" deeper than a 520 gear, and the bolts are larger, so the OBX would need to be drilled to accomodate the bolts.

I figure that I would check the gear mesh of the pinion shaft to the crown gear on final assembly and if that .010 difference on the face made it so the gears were offset, I could shim the carrier assembly to get the gears to line up, although I doubt that .010" will be a problem.

So....has anyone actually done this before ( I realize the machine work is cost prohibitive to some, but it seems like there are members on here with free access to machining), and if not is there anything you tranny gurus can think I am missing?

My biggest concern with the concept was whether the 3.85 gear could be machined, and that has been done.

[Tbird232ci]

I know this thread is a wee bit old now, but I was curious if a trans had been assembled with this setup, and working?

[Khajjathefang]

Interested

[83rampage]

I know this thread is a wee bit old now, but I was curious if a trans had been assembled with this setup, and working?

Unfortunately no the only progress I've made on this is obtaining the OBX, which I quickly tore apart to change the belleville washers and bolts, and it's still apart on the bench......

I was also wanting to modify the case for the Honda intermediate shaft bearing, but that has not made any progress either so the finished product is not really in sight right now, let alone the zero progress I've made on the Rampage lately. Jeez I still got a long way to go to be driving a TD again.

[jonnymopar]

WOW. This was a great thread to find, having an extra 555 in the basement. I've been wanting to go the OBX route, but I can't seem to find the 520 parts to do it.

Looking at the photos, the bolt circle seems different. Is it just how I'm looking at it? Could you post measurements of the distance between two opposite holes?

If the bolt pattern is indeed the same, you'd have to take away .040" of material (.080" diameter increase) for the M12 bolts. It doesn't seem like a huge amount of material, but I also don't have one right in front of me.

If I were to try to do this myself... is the 88 555 carrier the same as the 89? I know the gear sets are slightly different, but what about the diff on its own?

[135sohc]

Carrier/differential is all the same.

[83rampage]

Looking at the photos, the bolt circle seems different. Is it just how I'm looking at it? Could you post measurements of the distance between two opposite holes?

If the bolt pattern is indeed the same, you'd have to take away .040" of material (.080" diameter increase) for the M12 bolts. It doesn't seem like a huge amount of material, but I also don't have one right in front of me.

If I were to try to do this myself... is the 88 555 carrier the same as the 89? I know the gear sets are slightly different, but what about the diff on its own?

the point you bring up about the bolt circle is a valid one. I noticed it a while ago and was deciding how I will proceed.

Measuring the bolt circle center to center the 555 gear is about 1/16" bigger circle than the 520 (by a tape measure). The bolt circle if measured at the inner edge of the bolt holes is the same on both. So essentially to drill out the OBX properly you would need to drill the holes so the they were offset with more material removed towards the "outside" of the bolt circle. I'm thinking just enlarging the holes on the OBX won't work. Might have to talk to a machine shop anyway because just drilling the OBX is easier said than done because the material is so hard.

[GLHS60]

The carriers are the same but I have seen 3 types as to 4 pinion etc. One is totally drilled for 4 pinions, one has only one pair of holes but the other pair have bosses but not drilled and the third is only drilled for 2 pinions and doesn't even have bosses for the second pair.

Thanks
Randy

[trannybuster]

Why not just drill new holes bewteen the old? Looks the section area would be as large as the bolt shear area?

[83rampage]

Why not just drill new holes bewteen the old? Looks the section area would be as large as the bolt shear area?

That's a good idea. Leaves the option open to use a 520 ring gear in the future if desired. I like it.

[Pat]

the point you bring up about the bolt circle is a valid one. I noticed it a while ago and was deciding how I will proceed.

Measuring the bolt circle center to center the 555 gear is about 1/16" bigger circle than the 520 (by a tape measure). The bolt circle if measured at the inner edge of the bolt holes is the same on both. So essentially to drill out the OBX properly you would need to drill the holes so the they were offset with more material removed towards the "outside" of the bolt circle. I'm thinking just enlarging the holes on the OBX won't work. Might have to talk to a machine shop anyway because just drilling the OBX is easier said than done because the material is so hard.

You might want to ping James Reeves. He did some redrilling to run a Neon Quaife on a 3.05 ring gear. I don't remember if he drilled the quaife unit itself or if he re-drilled/tapped the ring gear.

[csxtra]

You might want to ping James Reeves. He did some redrilling to run a Neon Quaife on a 3.05 ring gear. I don't remember if he drilled the quaife unit itself or if he re-drilled/tapped the ring gear.

He re-drilled/tapped the ring gear.

[R/T]

He re-drilled/tapped the ring gear.

He had a machinist friend do it; it was a total PITA and burned up many expensive carbide bits if I remember.

He said never again....

[jonnymopar]

Might have to talk to a machine shop anyway because just drilling the OBX is easier said than done because the material is so hard.

He had a machinist friend do it; it was a total PITA and burned up many expensive carbide bits if I remember.

This is another thing I was kinda wondering about. I have no idea what type of materials we're dealing with here. I got my hopes up on the gear itself since the finish on the machined edge in the photos looks pretty clean.

[francois]

If he used carbided tips, I doubt that he threaded after..
In any case, that would mean that this is heat treated so using a tap made out of carbide is mostly unlikely because of the cost.
It would be easier to put that thing back in the oven to remove some hardness to make it easier to machine and then, bring back the rockwell higher.
The final drive must have had a heat treatment but probably not the differential.

[jonnymopar]

I have a 2500F oven at work, so annealing the parts first might be an option.

As far as the bolt circle being slightly different, if it is indeed only .060" or so off, that's ok. If the hole diameter in the OBX needs to be brought out .080" to accomodate the larger bolts, then you could actually go up to .080" in any direction without having an odd section of the 10mm hole left afterwards.

The next thing I'll be looking for when I pull my trans apart is whether the 12 holes are all exactly 30 degrees spaced out, or if there's a goofy offset one like on the end of a crank. Although, looking at the pictures, they do seem like they're equally spaced.

I REALLY hate thinking back about the two 520's I junked years ago. Even those high-mileage suckers would have told me everything I needed to know. Then again, every time I junk anything, I know it's only a matter of time until I wish I had it back for some stupid reason.

[trannybuster]

Hmm normally just the gears are induction hardened..Im not doubting they had trouble drilling and tapping but there are options/special taps. They tap hardened H13 here everyday at the shop. I wouldnt think the rockwell c would be above 52.....IDK

---------- Post added at 06:37 PM ---------- Previous post was at 06:33 PM ----------

^^Ive also seen them bore a hole in M2...58-60 rc

[francois]

Well, milling or machining using carbide will eventually remove material at some point that is not a problem. Threading past 50RC when the tool steel is at around 60rc...good luck unless you know something I don't know.
(For sure, I don't know everything but in any way, even with a brand new tap, I wouldn't dare to go back in the hole to push the thread further in a hole of a cutter made of D2 steel which was hardened at 58rc)

It might have been heat threaded only were the gears are. I am not aware of how they work in that kind of industry.
We built dies for car parts but not tranny or anything like that.

[trannybuster]

Dont read my thread and then reply to something I didnt even state.....I said Ive seen them bore M2, I didnt say they threaded it..??.....sheesh. I would say the ceiling is 50ish...

[black86glhs]

Dont read my thread and then reply to something I didnt even state.....I said Ive seen them bore M2, I didnt say they threaded it..??.....sheesh. I would say the ceiling is 50ish...

If you reread his, he is just stating what he feels he knows. Don't get all butthurt over it for crying out loud. He never specifically mentioned you.

[trannybuster]

^^No he's not, learn reading comprehension 101.."Threading past 50RC when the tool steel is at around 60rc...good luck unless you know something I don't know." Obvious he misconstrued the last bit I added about 58- "60"!
. Besides that my reply was pretty tame, YOUR making this out to be more than it is and butt hurt really, Im sure you know that feeling, I do not. Im not upset over a stupid post..?...perhaps you are? That okay mister protector? LOL...wtf.
BACK TO TOPIC I would try and drill the ring gear, just because a couple people found it diffuclt doesnt mean it isnt worth doing in your case...you may have a easier time of it, who knows..??...Keep us updated!

[cordes]

I'm not sure what the argument is about, but the ring gear is super hard. IIRC it's around 58 rockwell. The cheapest I've been quoted to drill and tap one is $350-$400 so far.

[jonnymopar]

I'm more interested in how difficult it would be to enlarge the holes on the OBX. Seeing a photo of the ring gear with the center taken out is enough info for me (other than the exact diameter of that cutout, which I believe is the number written on the 520 gear in the same pic).

I'd like to know what the material is for the outer case on the OBX diff. With the price, I'm sure there's no crazy exotic alloys anywhere in the assembly, but just how hard are we talking here?

[cordes]

I'm more interested in how difficult it would be to enlarge the holes on the OBX. Seeing a photo of the ring gear with the center taken out is enough info for me (other than the exact diameter of that cutout, which I believe is the number written on the 520 gear in the same pic).

I'd like to know what the material is for the outer case on the OBX diff. With the price, I'm sure there's no crazy exotic alloys anywhere in the assembly, but just how hard are we talking here?

It's not that hard at all. I have one that was a bit scratched up during shipping.

[francois]

I just wanted to add the experience that I have not creating a war or whatever.

He said.

They tap hardened H13 here everyday at the shop. I wouldnt think the rockwell c would be above 52.....

I said,

Threading past 50RC when the tool steel is at around 60rc...good luck unless you know something I don't know.


above 52 or less which I stated at 50, is pretty close, don`t you think?
;)
I even added paranthese after, just to make sure that I wasn`t trying to be a smart --- and I was open to learn. I guess I should have put a smilie in that case!

Btt.

If you only need to do clearance, it would be easy. Even if it`s hardened, just use a drill that has carbide tip, no need to be a fancy one. One that drill concrete will do the job. You can grind the side to have you desired diameter since the carbide is bigger.
I wouldn`t try to do that with a hand drill, off course.

I have a 568 here and I am planning to get an OBX very soon. This post is indeed interesting.

[83rampage]

I'm more interested in how difficult it would be to enlarge the holes on the OBX. Seeing a photo of the ring gear with the center taken out is enough info for me (other than the exact diameter of that cutout, which I believe is the number written on the 520 gear in the same pic).

I'd like to know what the material is for the outer case on the OBX diff. With the price, I'm sure there's no crazy exotic alloys anywhere in the assembly, but just how hard are we talking here?

My experience with the OBX hardness is very limited, but I can say on my unit a reasonably cheap drill bit won't touch it, but that was little more than a few minutes dicking around with it.

There is a new tool store close by that has expensive drill bits they claim will drill almost anything, so I may try that route. I just don't want to overly enlarge the ring gear holes to compensate for the difference in bolt circle if I can help it. Also Im fairly sure they are spaced out evenly (30 degrees)

I would have to think just drilling the OBX would be easier than drilling and tapping the ring gear. I can't see a quality unit such as an OBX having the heat treating the gear has either like was mentioned above.

[trannybuster]

The entire thing is 58 rc..?... probably surface is carburized and the tooth being hardened (as well as surface carb)..?... Depending on depth could grind down these spots surface wise then drill and tap, normally the bolt area is not through hardened, or so Ive been told buy some pedigree engineers. Not sure if heating the section at 1500 affects carburizng or not, do a web search. It would take some time as you wouldnt want to over heat the gear area but.....

[cordes]

The entire thing is 58 rc..?... probably surface is carburized and the tooth being hardened (as well as surface carb)..?... Depending on depth could grind down these spots surface wise then drill and tap, normally the bolt area is not through hardened, or so Ive been told buy some pedigree engineers. Not sure if heating the section at 1500 affects carburizng or not, do a web search. It would take some time as you wouldnt want to over heat the gear area but.....

When I saw the guy do the test he did it mainly near the bolt hole. He works at the prototype place in town and seemed impressed with how hard it was given the application, but who knows how hard that really is vs. other stuff out there?

[trannybuster]

^^Handy info..always nice to get a pro's thoughts. Im not saying everyone on here is ad-hock, but its a whole different story when you do it everyday for 20 years+...

[black86glhs]

^^No he's not, learn reading comprehension 101.."Threading past 50RC when the tool steel is at around 60rc...good luck unless you know something I don't know." Obvious he misconstrued the last bit I added about 58- "60"!
. Besides that my reply was pretty tame, YOUR making this out to be more than it is and butt hurt really, Im sure you know that feeling, I do not. Im not upset over a stupid post..?...perhaps you are? That okay mister protector? LOL...wtf.
BACK TO TOPIC I would try and drill the ring gear, just because a couple people found it diffuclt doesnt mean it isnt worth doing in your case...you may have a easier time of it, who knows..??...Keep us updated!

Nevermind.....it just isn't gonna do any good anyway.

[jonnymopar]

Ok, extra diff is finally out of the trans. I spent all last weekend doing other transmission work - stupid lawn tractor. The history is largely unknown for this extra 555 that I have, but I was pleasantly surprised at how good the teeth look on the ring gear and what I can see of the output shaft.

A couple of machinists that I work with talked me out of trying to hog the inside of the gear out myself. One of them shared a story of trying to do something similar in his younger days. The center section wasn't supported properly, and it jammed when he broke through the material, breaking his whole tool in half and really making a mess. I have limited machining experience, so I have someone that's going to water jet the gear for beer money, then I'll take it back and clean up the edge myself.

I'll be ordering the OBX and a moly plate soon. This old 555 should be a damn sturdy trans when it's done. We'll see how long my Turbo I axles last after this.

To the original poster: in your photo of the two gears, the 520 gear has "4.5885" written on it. I have no 520 gear or OBX to go by, so could you confirm that's the inner diameter of the 520 gear? Looking at the lip on the back of my 555 gear versus how much is left on the gear in your photos, it sounds like that number would be about right.

[83rampage]

Ok, extra diff is finally out of the trans. I spent all last weekend doing other transmission work - stupid lawn tractor. The history is largely unknown for this extra 555 that I have, but I was pleasantly surprised at how good the teeth look on the ring gear and what I can see of the output shaft.

A couple of machinists that I work with talked me out of trying to hog the inside of the gear out myself. One of them shared a story of trying to do something similar in his younger days. The center section wasn't supported properly, and it jammed when he broke through the material, breaking his whole tool in half and really making a mess. I have limited machining experience, so I have someone that's going to water jet the gear for beer money, then I'll take it back and clean up the edge myself.

I'll be ordering the OBX and a moly plate soon. This old 555 should be a damn sturdy trans when it's done. We'll see how long my Turbo I axles last after this.

To the original poster: in your photo of the two gears, the 520 gear has "4.5885" written on it. I have no 520 gear or OBX to go by, so could you confirm that's the inner diameter of the 520 gear? Looking at the lip on the back of my 555 gear versus how much is left on the gear in your photos, it sounds like that number would be about right.

When they did mine they used the plasma table to cut the middle out. Water jet would probably even work better.

As for confirming measurement your asking about I'll see what I can do. I have access to a good set of outside mics and snap guages so I can tell fairly close if it is right. Wont be as accurate as inside mics but close enough. Ill see if I can get that done tonight.

Edit. duh or I could measure the OBX with the outside mics.;)

[jonnymopar]

Thanks a lot. I appreciate it.

I don't even necessarily need that measurement all the way down to tenths. Hell, if you measured it with a halfway decent set of verniers, I'd be good.

Half-seriously, I put a want-to-buy thread up on the other forum asking if I could borrow a 520 gear, haha.

[83rampage]

I forgot to grab the gear last night to check with the good tools, so just now I checked it and with my $20 vernier I got 4.565".

I don't have much faith in the vernier so I already have the gear in the vehicle to take with me.

[83rampage]

Just checked my 520 ring gear with the outside mics. Confirmed 4.5885" is the proper dimension for the inner bore of the ring gear.

[jonnymopar]

Thanks for your help once again! I know what you're saying about a $20 vernier. I had one of those before I got a nice Mitutoyo coolant-proof 6" in trade for some PC repair!

It's like Christmas time! No turning back now. The gear is cut and the OBX is on it's way thanks to Chris at TU. I've been going crazy making measurements and taking tons of pictures. I measured a 139.5mm (5.492") bolt circle on the 555, which I measured off of the differential half (easier to measure the clearance holes in the diff rather than the threaded holes in the gear). We'll see what the bolt circle is on the OBX when it comes in.

The finish left by the water jet is far better than what I expected. I had him cut the gear to 4.540" so he had a nice big tolerance to work with. Now all that's left to do is clean up the I.D. on a lathe.


http://home.comcast.net/~jonnymopar/555obx/DSC_9638.JPGhttp://home.comcast.net/~jonnymopar/555obx/DSC_9639.JPGhttp://home.comcast.net/~jonnymopar/555obx/DSC_9640.JPG

[jonnymopar]

Ahh so close! I ran out of time at work.

http://home.comcast.net/~jonnymopar/555obx/DSC_9671.JPGhttp://home.comcast.net/~jonnymopar/555obx/DSC_9672.JPG


There's a radius on the OBX that was keeping the gear from sitting totally flat. The ID on the gear is what it needs to be, but I still need to relieve it near where it hits that radiused corner. I chamfered the gear when I turned the ID, but apparently it wasn't enough.


http://home.comcast.net/~jonnymopar/555obx/DSC_9670.JPG


It's getting there. I did some measurements with the CMM at work and got the following:

OBX bolt pattern: 5.3889"
OBX outer diameter: 6.1474"
OBX bolt hole size: 0.433" (11mm)
555 bolt pattern: 5.4890"
555 gear holes: M12x1.25

Here's the difference in the bolt pattern:

http://home.comcast.net/~jonnymopar/555obx/DSC_9677.JPG

I drew it up in CAD today, and after the correct bolt pattern is machined into the OBX, there will only be about a 0.088" wall between the outside of each bolt hole and the outer overall diameter on the OBX. Honestly, I'm not too concerned about it since that's not where all the forces are being exerted. Tomorrow, hopefully I'll get the gear set so I can start working with the differential.

[jonnymopar]

Huh... well I'll be...

http://home.comcast.net/~jonnymopar/DSC_9702.JPGhttp://home.comcast.net/~jonnymopar/555obx/DSC_9702.JPG
http://home.comcast.net/~jonnymopar/555obx/DSC_9704.JPG
http://home.comcast.net/~jonnymopar/555obx/DSC_9717.JPG
http://home.comcast.net/~jonnymopar/555obx/DSC_9718.JPG

In the close up of the bolt head, the chamfer on the edge of the OBX makes it look worse than it actually is.

Here's the new hole. A very small bit of the old hole is still there.

http://home.comcast.net/~jonnymopar/555obx/DSC_9713.JPG

I think even with the bolt head flanges hanging off the edge slightly, the amount of clamping force from twelve 12mm bolts should be plenty to hold this thing together.

Believe it or not, the OBX didn't machine too bad. It turns out it's only case-hardened. I used a 2-flute 1/2" carbide end mill for the first couple of holes, but it chattered a bit. I switched it out for a 4-flute and it cut beautiful. The mill didn't even look half bad once this was all done! I think the case hardening would've probably been enough to waste a high-speed steel end mill.

In the above picture, you can also get another look at the radius around where the gear ID sits. I put a 1/8" radius on the gear to clear it. It was a little bit more than I needed, but I didn't want it hanging up at all. Here's a closeup of the radius:

http://home.comcast.net/~jonnymopar/555obx/DSC_9708.JPG


MANY thanks to 83rampage for feeding me information as I've needed it. It was his idea anyway, and he's the one that took the first step of having a gear cut.

Hopefully this will be in the car within the next couple of weeks. I've got the new bearings, bearing shims, and a chrome moly plate waiting. Last piece of the puzzle is getting my flywheel back and receiving my new Turbos Unleashed clutch!

[cordes]

Congrats. That was a heck of a project. If you don't mind my asking, what do you think a normal shop would charge to do that job?

[jonnymopar]

I should find out. I've got at least 5 hours into it myself, but I was really taking my time, making tons of measurements and taking pictures. If you went in with a list of already-defined measurements, it would take a lot less time. However, I'm not even sure exactly how much time it took to water jet the core of the gear out, so add that in.

Also, I forgot to mention (even though it's readily evident in the pictures): there were no issues using the leftover 555 ring gear bolts. The OBX bolt flange is only 0.025" thinner than the 555 flange, so the bolt length was fine.

[cordes]

Thanks. When I grenade the trans in my blue omni I'll have to decide what I want to do with my FD in the next one for the OBX and this info will really help to make a choice.

[Khajjathefang]

Im licking my chops at this and thinking of that third unused 555 in my garage...

[trannybuster]

Nice....beat down for the 'its too hard(pun) naysayers. Ive seen some pretty hard stuff machined, watched old timer drill a hole in hardened M2!! He said the tough part isnt drilling the hole, it was stopping...lol...something about it was iffy if the bit didnt just shatter.He also commented the had made a square hole using an engine lathe..beyond me, but he wasnt one to bs....that def. looks good. Nice thing about case hardening, normally its only soooooo deep and heat will wipe it away.

[jonnymopar]

I can't wait to get this thing in. Getting the gear on there only confirms 90% of the information I need though. The finish line is when I see how well it mates up with the output shaft gear. 83rampage mentioned earlier that the 555 gear is a slightly different thickness than the 520 gear. If it's only .010" or so as he said, I won't be concerned.

If this whole thing bolts together without any issues, it may be one of the first true drop-in limited slip setups for the 555/568. Let's hope it doesn't puke the first time I dump the clutch at 5500rpm!

[trannybuster]

Blasphemy......well they handle high hp so even if you knocked down the strength 10% wont matter.....itll hold....

[jonnymopar]

With your user name, I tend to believe you, haha.

[cordes]

Nice....beat down for the 'its too hard(pun) naysayers. Ive seen some pretty hard stuff machined, watched old timer drill a hole in hardened M2!! He said the tough part isnt drilling the hole, it was stopping...lol...something about it was iffy if the bit didnt just shatter.He also commented the had made a square hole using an engine lathe..beyond me, but he wasnt one to bs....that def. looks good. Nice thing about case hardening, normally its only soooooo deep and heat will wipe it away.

It's not so hard that it can't be machined. It's so hard that the cost of having the machine work done makes other choices the better option. In my area the cost to have this done would put me into custom ring gear territory.

[jonnymopar]

Make no mistake, this is something that's only worth it IF:

1. You have the means to do most or all of it yourself, or
2. You want a 3.85 final in your 555 enough where you'd be ok with the added cost of someone doing it for you.

Also, even at this point, I'm reluctant to have any faith in it until I beat on it at least little bit and it lives. I know the 555 is strong and I know the OBX is too. While I've got those two things going for me, it doesn't prove anything in this case.

Cordes, I'd go for the 3.50 final in an Omni anyway. In a big fat stock-weight T-top turbo Daytona, it's a little different.

[trannybuster]

^^^^ True and ^^True...it would get expensive IF you had all this work done by a shop.

[83rampage]

I can't wait to get this thing in. Getting the gear on there only confirms 90% of the information I need though. The finish line is when I see how well it mates up with the output shaft gear. 83rampage mentioned earlier that the 555 gear is a slightly different thickness than the 520 gear. If it's only .010" or so as he said, I won't be concerned.

If this whole thing bolts together without any issues, it may be one of the first true drop-in limited slip setups for the 555/568. Let's hope it doesn't puke the first time I dump the clutch at 5500rpm!

I'm glad to see the progress you have made on this. My project stalled so I'm going to have to get it back on track.

It will be interesting to see how it all lines up in the trans. The .010" comment I made was based on some very crude measurement and my trusty $20 dial caliper, but I would be confident it's close enough not to worry about it.

As for how it will hold up I don't see anything that would concern me any more than the way it came factory. It'll be fine.

For me, my "free" machine work source more or less dried up, so when it comes to getting the holes enlarged for the M12 bolts I'll have to cough up for a machine shop to do it since it isnt a case of simply enlarging the holes. Not a biggy though, the most expensive work is already done.

Looks good. Keep us posted.

[jonnymopar]

Well, all that's left to do is heave the transmission back in the car. The OBX is in, along with a chrome moly plate! I left the camera in the garage and I'm in for the night, so I'll post pictures tomorrow.

While I was setting the preload on the carrier bearings, I noticed that the ring gear was hanging off the intermediate shaft gear a little more than I wanted. It was hanging off toward the passenger side (aluminum extension housing). I figure I have two choices:

1: Make a shim that fits between the ring gear and the OBX
2: Add the carrier bearing shims to the extension housing instead of the steel bearing retainer

I tend to trust option 2 more, so that's what I did. I took the original shim out of the steel side, added it to the aluminum side plus another .020" because that's what I needed for proper preload. After that, the gear appears to be in a happier place, and the turning torque was perfectly in spec. I'm sure either of the above two options would work, but I was able to do this without any extra parts. Plus, the gear was torqued and loctited on there already and I don't want to take it apart for a third time.

So, we're 99% of the way there. I really hope to enjoy the sunset through T-tops tomorrow night.

[jonnymopar]

It's in... and it's GOOD! I've never had a car with limited slip before, and holy crap, this thing is awesome in the exit ramps! With the new clutch, obviously I haven't done any crazy launches yet, but no problems so far.

Here's the money shot, complete with OBX logo looking right at you:

http://home.comcast.net/~jonnymopar/555obx/diff_installed.jpg

I tried to get a picture of how the ring gear meshes with the intermediate shaft gear, but this is all I could get:

http://home.comcast.net/~jonnymopar/555obx/gear_mesh.jpg

The gears are not off by much. Again, I had to add the diff bearing shims to the other side, but it turned out fine. I asked my attack spider and he said it was ok:

http://home.comcast.net/~jonnymopar/attack_spider.jpg

I want to get as many miles on this as I can before I drive it to Chrysler Carlisle this year. After only 70ish miles so far, everything feels so much tighter now between the new clutch and having all the slop taken out of the trans bearings.

So there you go! Anybody that wants to try this on their own 555, there should be enough info in this thread to make it happen. If I missed anything, hit me up. Once again, a huge thanks to 83rampage for helping me out with this and having the vision early on that this might just work.

[83rampage]

Excellent work getting this done. If it was up to me the proof of concept would not have happened for years.

I do have a question about your final set up however.

You first observed that the ring was hanging off the passenger side of the i-shaft so you switched the shim to the other side of the diff carrier.

From the pictures it looks like it is now possibly hanging off the drivers side (I looked and confirmed the i-shaft gear is wider than the ring gear so it may be even on the drivers side). Just wondering if getting 2 shims made and splitting the differnce would have been closer to the middle of the i-shaft gear. I know it would mean more machine work, but i'm just curious.

Looking at my i-shaft based on the wear pattern of the factory set up, the ring gear is clearly biased to the drivers side, so your probably right on the money as long as it doesn't hang off the drivers side.

Besides, if it is attack spider approved, its got to be good.

[trannybuster]

Good stuff!

[jonnymopar]

Excellent work getting this done. If it was up to me the proof of concept would not have happened for years.

I do have a question about your final set up however.

You first observed that the ring was hanging off the passenger side of the i-shaft so you switched the shim to the other side of the diff carrier.

From the pictures it looks like it is now possibly hanging off the drivers side (I looked and confirmed the i-shaft gear is wider than the ring gear so it may be even on the drivers side). Just wondering if getting 2 shims made and splitting the differnce would have been closer to the middle of the i-shaft gear. I know it would mean more machine work, but i'm just curious.

Looking at my i-shaft based on the wear pattern of the factory set up, the ring gear is clearly biased to the drivers side, so your probably right on the money as long as it doesn't hang off the drivers side.

Besides, if it is attack spider approved, its got to be good.

Looking back at that post, I should really re-word it. By hanging off, I was more referring to the wear pattern on the gear. Which, exactly as you said, is more on the driver's side. I found that adding the bearing shims to the other side lined up the gear perfectly with the existing wear pattern. I don't think it was actually sticking out further than the intermediate shaft gear, it was just pushed over to the other side of it. While that probably would have worked too, I wanted to put the gear right back where it was originally if possible. I must have taken 10 pictures from that same spot trying to capture how the gears meshed. When I get a chance, I'll try to find the best one and link to a full-resolution picture. Hopefully I've got one where you can see the wear pattern on the intermediate shaft gear.

The bearing shim pack that I bought included ten .005" shims, so you probably wouldn't have to machine anything. My stock spacer was exactly .050", and if it came down to putting that on one side and making up the difference on the other side, I don't think there would be any issues. I happened to like where it sat with all the spacers on one side.

As for the attack spider, I'm glad I found it before my wife did. I scooped that sucker up in my basement! I flung him out in the garage, figuring there's plenty to eat out there.