3.05FD Hybrid trans facts

[cordes]

I thought I would put together a quick post with some information to help out folks doing a hybrid trans and for anyone thinking of going with a gear out of a 525 regardless of the FD.

1. You will need to have the ring gear machined to accept the larger 520 or OBX diff. when using the 525 ring gear. You will need new holes drilled in the ring gear 8 new ones and 4 will be bored out larger.

2. 4 of the 525 ring gear holes almost line up so the machinist will radius the holes in the diff ever so slightly so that those can be used.

3. With the OBX I have, my machinist will probably need to open it up some so that it is not a press fit to get the 525 ring gear onto the diff.

4. If you look at DJ's build thread he shows how he swapped everything on the main shaft. I followed his directions and that worked out almost perfectly. I was able to remove everything from the 525 set with only two screwdrivers. However, the 555 set required the bearing splitter he used and also a very large 3 jaw puller to get 2nd gear off the shaft.

http://www.turbo-mopar.com/forums/showpost.php?p=519876&postcount=27

5. The 525 main shaft uses a different method of stopping the thrust washer from spinning than the 555. The 525 pieces fit into two recesses on each side of the shaft with a solid retaining ring around them. The 555 has two pieces held in place with a snap ring and an anti-spin pin in the shaft. You will need to use whichever thrust setup came with that shaft. The anti-spin pin and thrust washer under 1st is the same for both shafts though.

Here is a graph of what the 3.05FD will look like with the 555 gear set and 205/50r15 tires.



Gear Mph per 1000 RPM Mph @6500 RPM
----------------------------------------
1 7.50 49
2 11.91 77
3 17.58 114
4 23.94 156
5 31.69 206

Mph RPM (in Gears)
-------------------------------------------------
1 2 3 4 5
-------------------------------------------------
5 667 420 284 209 158
10 1333 840 569 418 316
15 2000 1260 853 627 473
20 2666 1680 1138 835 631
25 3333 2100 1422 1044 789
30 4000 2520 1706 1253 947
35 4666 2940 1991 1462 1104
40 5333 3360 2275 1671 1262
45 5999 3780 2560 1880 1420
50 4200 2844 2089 1578
55 4619 3129 2298 1735
60 5039 3413 2506 1893
65 5459 3697 2715 2051
70 5879 3982 2924 2209
75 6299 4266 3133 2366
80 4551 3342 2524
85 4835 3551 2682
90 5119 3760 2840
95 5404 3968 2997
100 5688 4177 3155
105 5973 4386 3313
110 6257 4595 3471
115 4804 3628
120 5013 3786
125 5222 3944
130 5430 4102
135 5639 4259
140 5848 4417
145 6057 4575
150 6266 4733
155 6475 4891
160 5048
165 5206
170 5364
175 5522
180 5679
185 5837
190 5995
195 6153
200 6310
205 6468

Gear Change RPM drop (change @6500)
---------------------------------------
1 -> 2 -2405 (to 4095)
2 -> 3 -2098 (to 4402)
3 -> 4 -1727 (to 4773)
4 -> 5 -1590 (to 4910)




Ring gear bolts:

A-525 M10x1.25 70ft.lbs.
A-523, A-543 M10x1.0 65ft.lbs.
A-568 M12x1..25 80ft.lbs.


If Reeves or anyone has something to add please do. Thus far everything has been easy enough on this project that I'm thinking of making more. The hardest part is finding a trans in the yard these days.

[Vigo]

This post and the one you linked to are good stuff! I had a 555 apart one time many years ago but DJs post seemed like almost new info even to me, great refresher.

Your gear chart is interesting stuff..

So, maybe this isnt the thread to discuss merits, but what is the main purpose of this?

I can see it having two purposes: making it easier to get traction in 1st and 2nd, and upping mpg. I can also see it making 3rd much more attractive on the highway for WOT, though i doubt thats a motivating factor.

However, unless im mistaken it is NOT intended in any way to address the strength issues of a 525 like case distortion, etc?

I have an interesting comparison. My honda insight has similar gearing to what this 3.05 fd would be. However, in my case since i have almost no torque to work with, and hills everywhere i go, it ends up meaning that i rarely ever use 5th. 4th is about .8 and 5th is about .6, fd is 3.2, and tires are ~22.5", a bit shorter than 205/50r15.

A 2.2 omni, turbo or not, has a much better torque/weight ratio than my insight, so given the same gearing it would probably work better, but you'd probably still have to use a significant amount of throttle in 5th to maintain speed up a hill.

Anyway, good info!

[cordes]

This post and the one you linked to are good stuff! I had a 555 apart one time many years ago but DJs post seemed like almost new info even to me, great refresher.

Your gear chart is interesting stuff..

So, maybe this isnt the thread to discuss merits, but what is the main purpose of this?

I can see it having two purposes: making it easier to get traction in 1st and 2nd, and upping mpg. I can also see it making 3rd much more attractive on the highway for WOT, though i doubt thats a motivating factor.

However, unless im mistaken it is NOT intended in any way to address the strength issues of a 525 like case distortion, etc?

I have an interesting comparison. My honda insight has similar gearing to what this 3.05 fd would be. However, in my case since i have almost no torque to work with, and hills everywhere i go, it ends up meaning that i rarely ever use 5th. 4th is about .8 and 5th is about .6, fd is 3.2, and tires are ~22.5", a bit shorter than 205/50r15.

A 2.2 omni, turbo or not, has a much better torque/weight ratio than my insight, so given the same gearing it would probably work better, but you'd probably still have to use a significant amount of throttle in 5th to maintain speed up a hill.

Anyway, good info!

Thanks. You have pretty much identified the reasons for my doing the switch.

In order of importance to me they are as follows.

1. I found a 3.05FD setup before I found a 3.50 setup.

2. These days my Omni mainly takes road trips across several states at cruising speed. So this makes sense for my mpgs. Also, we live in the flattest county in the prairie state. You can see the horizon in almost all directions in the winter so I will be able to cruise in 5th at 55-60mph even with this gearing.

3. Traction should not be an issue any longer. Now I will need to worry about making enough power to turn this gear.

I'm actually using the 3.05FD gear set out of the 525 to make a 3.85FD 555 hybrid for my dad who is making a Horizon off road vehicle. I figure this will give him the steepest gear possible. It's not as crazy as I had hoped for, but it is as high as we go. Since everything will be in a 555 case with a 555 diff I think it should stay alive much longer than if it were in a 525 case with off road intent.

[Reeves]

Couple things to change.

I did not need to machine the I.D. of my ring gear at all to fit on my Quaife. It was a perfect snug fit.

4 of the clearance holes on the Quaife almost line up with 4 of the tapped holes in the 3.05 ring gear. I needed to machine the holes about 3mm if memory serves me right.

Then add 8 new tapped holes to the ring gear, for a total of 12 bolts being used, just like a normal 520 ring gear.

I also think that I used the 525 diff bolts in the 4 tapped holes that line up, and then when I added the 8 additional holes, I used the bigger 520 bolts.

Edit: Had some trans numbers wrong above. Fixed now.

[bakes]

Reeves were you running 525 shafts in a 555 case or the otherway around?

[Reeves]

I'm running 555 gearset in a 555 case with 525 3.05FD main shaft and ring gear.

[Reaper1]

Very interesting! I like what I see here! :thumb:

[Reeves]

520 3.50fd ring gear left / 525 3.05 ring gear right on 520 Quaife diff

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13254&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13254')

520 stock diff bolt left / 525 stock diff bolt right

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13249&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13249')

Pic of the (8) new holes added to 525 3.05fd ring gear. Also shown is (1) bolt in the (4) holes that almost line up (after machining/slottin the (4) of the clearance holes in the quaife)

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13243&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13243')

Pic of the stock 525 diff

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13244&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13244')

Pic of the 525 3.05fd with the (8) new tapped holes added. Note the chamfers.....this was to get by the case hardness.

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13245&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13245')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13250&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13250')

Pics of the slotted holes in the Quaife.

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13246&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13246')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13247&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13247')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13248&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13248')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13248&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13248')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13251&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13251')

http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13252&thumb=1 ('http://www.turbo-mopar.com/forums/attachment.php?attachmentid=13252')


Found these pics of when I built mine. They may be helpful?

[Vigo]

Thanks for that!!!

[rbryant]

Couple things to change.

I did not need to machine the I.D. of my ring gear at all to fit on my Quaife. It was a perfect snug fit.

4 of the clearance holes on the Quaife almost line up with 4 of the tapped holes in the 3.05 ring gear. I needed to machine the holes about 3mm if memory serves me right.

Then add 8 new tapped holes to the ring gear, for a total of 12 bolts being used, just like a normal 555 ring gear.

I also think that I used the 525 diff bolts in the 4 tapped holes that line up, and then when I added the 8 additional holes, I used the bigger 555 bolts.

Excellent work!

Just so someone doesn't order the wrong thing it should be stated that this was a Neon quaife not a 555/568 quaife. The 555/568 style differential wouldn't have worked because it has a different ring gear design.

Also I think this is limited to the 87/88 555 (or a 520) and wouldn't work on the newer '89+ 555/523/568 transmissions due to the way they changed the main gear in '89 and later transmissions.



The cool thing is that this avoids all of the weak 525 parts! It actually makes something off from a 525 transmission cool (and that is quite an accomplishment).

Is the 525 ring gear the same width/strength as a 520 ring gear?

IIRC the 555 is a little stronger than the 520 but it still shouldn't be an issue. The bolt holes also line up in a safe place to drill/tap what a stroke of luck!


I am pretty sure that the 555 ring gear bolts are actually bigger than the 520 ring gear bolts. I remember this because I accidentally had the impact wrench on tighten and snapped one off from the 523 ring gear when I did my hybrid 568/OBX. I went to use the 568 bolt and it was bigger so I ended up buying a new set for a neon... (PN: 5017180AA $1.50ea) Of course this is assuming that the 568 bolts weren't larger than the 555 bolts....

Are the Lbody bolts the same size as the 520/523 bolts or are they even smaller?

If you used the 555/568 bolts It seems like they would have been larger than the holes in the neon obx/quaife differential that is designed for the 520/523 sized bolt. Did you have to enlarge the holes in the diff or were they already large enough to take a bigger bolt?


-Rich

[Reeves]

Excellent work!

Thanks! And Thanks to my machinist Mike Oaks and to Warren Hall for the re-assembly.


Just so someone doesn't order the wrong thing it should be stated that this was a Neon quaife not a 555/568 quaife. The 555/568 style differential wouldn't have worked because it has a different ring gear design.

Correct. It is a Neon Quaife or as some call it a 520 Quaife. It's the same Quaife you have to use if you are going to run a hybrid 3.50 trans as well (which is what my trans used to be).


Also I think this is limited to the 87/88 555 (or a 520) and wouldn't work on the newer '89+ 555/523/568 transmissions due to the way they changed the main gear in '89 and later transmissions.

I'm not so sure what all they changed besides the sleeve on the main shaft bearing on the diff side and a larger bearing. Were their other changes in 89+ 555's?




The cool thing is that this avoids all of the weak 525 parts! It actually makes something off from a 525 transmission cool (and that is quite an accomplishment).

Is the 525 ring gear the same width/strength as a 520 ring gear?

Overall width is the same. Gear pitch/thickness of teeth is different. The stock 555 and even the 3.50fd 520 has a much coarser design that looks to be more beefy. But, I have quite a few passes on the 3.05fd right now and it looks to be holding up great.


IIRC the 555 is a little stronger than the 520 but it still shouldn't be an issue. The bolt holes also line up in a safe place to drill/tap what a stroke of luck!


I am pretty sure that the 555 ring gear bolts are actually bigger than the 520 ring gear bolts. I remember this because I accidentally had the impact wrench on tighten and snapped one off from the 523 ring gear when I did my hybrid 568/OBX. I went to use the 568 bolt and it was bigger so I ended up buying a new set for a neon... (PN: 5017180AA $1.50ea) Of course this is assuming that the 568 bolts weren't larger than the 555 bolts....

Are the Lbody bolts the same size as the 520/523 bolts or are they even smaller?

If you used the 555/568 bolts It seems like they would have been larger than the holes in the neon obx/quaife differential that is designed for the 520/523 sized bolt. Did you have to enlarge the holes in the diff or were they already large enough to take a bigger bolt?


-Rich

The bolts in the 520 are bigger than the bolts in the 525. Also, the 520 bolts are a finer thread. I used (4) of the stock 525 bolts in (4) of the stock 525 ring gear tapped holes. Then we added the bigger/finer tapped holes (8) to the ring gear and used the 520 bigger/finer bolts. You can see this in the pics I think.

[Reeves]

I added description to my pictures above. These may help.

[cordes]

Thanks for adding all of those pics Reeves. That saved me a lot of work.

[rbryant]

I'm not so sure what all they changed besides the sleeve on the main shaft bearing on the diff side and a larger bearing. Were their other changes in 89+ 555's?



The 89 520/555 has the same internals as a 523/568: That means that the 2nd gear and synchros are totally different. It is the same reason that 88 and older parts can't be mixed with 89 and newer parts when making a hybrid transmission. The 525s were all 88 and older style transmissions so their parts can't be used with a 523/568.

http://www.turbo-mopar.com/forums/vbarticles.php?do=article&articleid=80



The bolts in the 520 are bigger than the bolts in the 525. Also, the 520 bolts are a finer thread. I used (4) of the stock 525 bolts in (4) of the stock 525 ring gear tapped holes. Then we added the bigger/finer tapped holes (8) to the ring gear and used the 520 bigger/finer bolts. You can see this in the pics I think.

Ok that makes sense. The 555/568 ring gear bolts are even bigger than the 520/523 ring gear bolts. That was the only thing that confused me because I think you said you used 555 ring gear bolts accidentally.

-Rich

[Juggy]

The 89 520/555 has the same internals as a 523/568: That means that the 2nd gear and synchros are totally different. It is the same reason that 88 and older parts can't be mixed with 89 and newer parts when making a hybrid transmission. The 525s were all 88 and older style transmissions so their parts can't be used with a 523/568.

http://www.turbo-mopar.com/forums/vbarticles.php?do=article&articleid=80



Ok that makes sense. The 555/568 ring gear bolts are even bigger than the 520/523 ring gear bolts. That was the only thing that confused me because I think you said you used 555 ring gear bolts accidentally.

-Rich

couldnt u just use the 1/2 gear from the 520 then the 3/4 from the 568...if this were the case??

wish i didnt get rid of my 89 555 since i have a bunch of 568s lol

[Reeves]

The 89 520/555 has the same internals as a 523/568: That means that the 2nd gear and synchros are totally different. It is the same reason that 88 and older parts can't be mixed with 89 and newer parts when making a hybrid transmission. The 525s were all 88 and older style transmissions so their parts can't be used with a 523/568.

http://www.turbo-mopar.com/forums/vbarticles.php?do=article&articleid=80



Ok that makes sense. The 555/568 ring gear bolts are even bigger than the 520/523 ring gear bolts. That was the only thing that confused me because I think you said you used 555 ring gear bolts accidentally.

-Rich


Oops, I may have said 555 bolts. Sorry.

Also, the link you sent, it looks like the 1-2 synchro is the only one that is different? So maybe you could use the old 1-2 style synchro stuff in the later trans when using different main shafts?

[86Shelby]

Also, the link you sent, it looks like the 1-2 synchro is the only one that is different? So maybe you could use the old 1-2 style synchro stuff in the later trans when using different main shafts?

That very well may be possible on the 555/520s for 88 and 89; using an 89 multi piece synchro shaft & gears in an 88 case and vise versa. That would not be possible between the 523/568 and 555 due to the different diameter roller bearing on the end.

The nice thing is that all 555s and 568s used the same 3-4 gears and brass, so finding a good one is easier. Synchro parts, likely the slider/ring may be different between the two due to the different fork pads used.

[Juggy]

rich can I mix a 90 523 with a 91+ 568??? for hybrid reasons of course...then id take the 523 gears on the 3.85 to make a quick gearing trans, then i could use a quaife in a 523 geared 3.85 trans...

just trying to figure out what i can do with what "trannys" i have lol

[rbryant]

rich can I mix a 90 523 with a 91+ 568??? for hybrid reasons of course...then id take the 523 gears on the 3.85 to make a quick gearing trans, then i could use a quaife in a 523 geared 3.85 trans...

just trying to figure out what i can do with what "trannys" i have lol

Yes the 523s and 568s are all compatible.

-Rich

[rbryant]

That very well may be possible on the 555/520s for 88 and 89; using an 89 multi piece synchro shaft & gears in an 88 case and vise versa.

I believe that there is some issue with the mounting of the synchros that would have to be resolved in order to mix and match the early and late 520/555 parts. I haven't heard of anyone doing it.



That would not be possible between the 523/568 and 555 due to the different diameter roller bearing on the end.

The nice thing is that all 555s and 568s used the same 3-4 gears and brass, so finding a good one is easier. Synchro parts, likely the slider/ring may be different between the two due to the different fork pads used.

Good point, the shafts are slightly different on the 89 555 and 568.

The gears 1-5 on the '89 555 are the same as the 90 568 (91+ 568s have a shorter 1st gear). The bearing would be a problem on the main shaft if you were to try and put a 555 shaft in a 568. Perhaps the 555 shaft could be sleeved to use the larger bearing but who knows.

Are the synchros the same between the 523 and 568 aswell? It seems like I had them both in my hands once and didn't see a difference.

-Rich

[TurboGLH]

I mentioned last night in a PM to James that it may be possible to use the 523/568 slider on the early hub to allow use of a early shaft in a 523/568. I don't know for sure, but it is a possibility.

This would allow use of any shaft in any year, with a careful mixing of parts. Including allowing for a 3.05 f/d in a 568.

I mentioned it because earlier parts are harder to find, but with the 3.05 he's kind of locked himself into using 88 and earlier parts.

If anyone has easy access to a 88 earlier and 89+ 1/2 synchro assy, a quick check if the later model slider fits the early hub would give a solid answer.

Also the issue of the larger mainshaft bearing is easily solved by installing the sleeve used on the 523/568 onto the early shaft. It's somewhere around $50 from the dealer, but still avail at this point.

edit: In answer to the above question, yes 523 and 568 synchro's are the same, year for year. 90 is all by itself, with 91+ sharing the same parts.

[rbryant]

edit: In answer to the above question, yes 523 and 568 synchro's are the same, year for year. 90 is all by itself, with 91+ sharing the same parts.

Interesting...

Are the differences from 90 to 91 related to the first gear or something or was there actually a change in the syncrho setup?

Can you change the 90 568 to a 91+ style syncrho or is the different 1st gear a problem?

Thanks,

Rich

[TurboGLH]

Interesting...

Are the differences from 90 to 91 related to the first gear or something or was there actually a change in the syncrho setup?

Can you change the 90 568 to a 91+ style syncrho or is the different 1st gear a problem?

Thanks,

Rich

Related to the unique 90' only 1/2 shift fork/pad/slider assy only, the gear makes no difference. The 90' pads are smaller than the 91+ and chryco upgrades them to a much beefier setup in 91 (the pad it self is larger) and changed the fork and slider to accommodate the larger pad.

[cordes]

I mentioned last night in a PM to James that it may be possible to use the 523/568 slider on the early hub to allow use of a early shaft in a 523/568. I don't know for sure, but it is a possibility.

This would allow use of any shaft in any year, with a careful mixing of parts. Including allowing for a 3.05 f/d in a 568.

I mentioned it because earlier parts are harder to find, but with the 3.05 he's kind of locked himself into using 88 and earlier parts.

If anyone has easy access to a 88 earlier and 89+ 1/2 synchro assy, a quick check if the later model slider fits the early hub would give a solid answer.

Also the issue of the larger mainshaft bearing is easily solved by installing the sleeve used on the 523/568 onto the early shaft. It's somewhere around $50 from the dealer, but still avail at this point.

edit: In answer to the above question, yes 523 and 568 synchro's are the same, year for year. 90 is all by itself, with 91+ sharing the same parts.

I would strongly agree with your assessment. After digging into a few transmissions now, I can see where will will be able to make combinations that will allow for massive parts interchange and keep many more of these units serviceable. I certainly won't be passing up the opportunity to pull the synchro assemblies out of 525s any longer.

[rbryant]

Related to the unique 90' only 1/2 shift fork/pad/slider assy only, the gear makes no difference. The 90' pads are smaller than the 91+ and chryco upgrades them to a much beefier setup in 91 (the pad it self is larger) and changed the fork and slider to accommodate the larger pad.

Does this mean that if someone is doing a hybrid '90 568 with a 91+ 523 and they should swap out the 523 shift fork/pads/slider assembly into the 90 568?

If so I wish I knew about that a few years back...

-Rich

[TurboGLH]

I would strongly agree with your assessment. After digging into a few transmissions now, I can see where will will be able to make combinations that will allow for massive parts interchange and keep many more of these units serviceable. I certainly won't be passing up the opportunity to pull the synchro assemblies out of 525s any longer.

I would look myself, but I don't really do car stuff anymore, plus my dads garage is in disarray while we do the finish work on his new addition.


Does this mean that if someone is doing a hybrid '90 568 with a 91+ 523 and they should swap out the 523 shift fork/pads/slider assembly into the 90 568?

If so I wish I knew about that a few years back...

-Rich

I would. Not necessary though. If you used the full 90' synchro's and the 91 523 shaft, you have a 90' 523/568. If you had switched the sliders, you would have a 91' 523/568. The 90 pads are NS1 *i think*, it's hard to keep track, so I could be mixing them up with another year/gear.

If you ever *have* to pull the gearset for some reason.....like changing a shift fork pad. Take the time, if you can get new 91+ 1/2 pads and swap out the slider, should last longer than the 90' ones did/will.

If i recall correctly, the 90' 1/2 pads are closer in size the the 3/4 pads, vs the much larger and more durable 1/2 pads used 91+

[cordes]

I'll be adding the following information to the OP. If anyone has the 555 and 520 bolt specs for sure please post them up. I've taken this info from my 90' FSM

Ring gear bolts:


Ring gear bolts:

A525 M10x1.25 70ft.lbs.
A-523, A-543 M10x1.0 65ft.lbs.
A-568 M12x1..25 80ft.lbs.

I think I'm just going to use the 525 bolts for my ring gear after seeing this info. If anyone has a different opinion based on the thread pitch let me know.

[rbryant]

I'll be adding the following information to the OP. If anyone has the 555 and 520 bolt specs for sure please post them up. I've taken this info from my 90' FSM

Ring gear bolts:


Ring gear bolts:

A525 M10x1.25 70ft.lbs.
A-523, A-543 M10x1.0 65ft.lbs.
A-568 M12x1..25 80ft.lbs.

I think I'm just going to use the 525 bolts for my ring gear after seeing this info. If anyone has a different opinion based on the thread pitch let me know.

It probably doesn't really matter. The torque on the fine threads will be more accurate and you will get more threads engaged so the fine thread is probably slightly better. Considering that they also upgraded the number of bolts on the 523 diff it should be fine.

The larger M12 bolts were probably required because they are both holding the ring gear on and compressing the diff case on the 555/568.

Use loctite on either fine or course thread M10 bolts and all should be good.

One other practical reason to use the 523 bolts is that if you are doing a side by side swap you will have enough 523 bolts but not enough 525 bolts to do the job.

-Rich

[cordes]

It probably doesn't really matter. The torque on the fine threads will be more accurate and you will get more threads engaged so the fine thread is probably slightly better. Considering that they also upgraded the number of bolts on the 523 diff it should be fine.

The larger M12 bolts were probably required because they are both holding the ring gear on and compressing the diff case on the 555/568.

Use loctite on either fine or course thread M10 bolts and all should be good.

One other practical reason to use the 523 bolts is that if you are doing a side by side swap you will have enough 523 bolts but not enough 525 bolts to do the job.

-Rich

Thanks Rich. That is pretty much what I was thinking. I have a bunch of 525 bolts lying around so I will probably use those.

[135sohc]

The 523/568 1-2 synchronizer slider does fit the 87/88 555/520 1-2 synchronizer hub. Not sure about an 89 since I dont have one of those yet but I bet its the same.

Not totally out of the woods though. Would have to use the 87/88 1-2 gears and that cuts out using a 92+ 523 or 568 gearset since the 1st gear changed on the 568 and the 92+ 523 is of course is its own unique gearset.

[cordes]

That's one more part that will work though. Thanks a ton for the info.