A555 -3.85 FD with an OBX

[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:



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



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:



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.