SJC5

Hey gang,

I'm preparing to swap out my 2.73 with a 3.42 3-rib differential I bought from a forum member. This differential came off his 2002 Z06 with about 90K miles on the clock.

It's going onto my 2004 A4 base coupe. I want to do this right the first time and need your thoughts on what I need as far as seals/gaskets etc...

I also plan to drain and refill the unit.

Appreciate any help!

Rob Petyo

You're gonna love it... you might want to think about going with a new stahl converter while your at it.

MikeV

All depends on how you drive. If you just drive 2k miles a year, just change the stub shaft seals and install with new orings. If you drive your car, I would have it gone through and replace bearings and clutches. If you plan on drag racing, I would upgrade to hardened shafts. By the way use a good corvette specialist for the work as nothing is worst than having a whine after everything is done.

Mike V

SaberD

if you bought the full diff with the carrier and it's in good shape and no whine, here is what i'd do:

-axle seals, and grease them up.
-new differential to transmission o-ring
-left and right hand cover o-rings.
-Remove the left hand cover, and clean off the circular magnet resting in the slot. (It's going to be horribly disgusting.)

And if you have access to a press, you can replace the clutch packs and belleville washers. You just need to press down on the output shaft around the cross pin that holds the spider gears to compress the washer to remove/install the cross pin. There is a kent moore tool for this, but you can probably make your own out of something as simple as a block of wood. I can almost guarantee you the belleville washers are cracked rendering the limited slip function of the differential practically useless. Chances are if the washer is cracked, you won't even need to press on the output shaft to remove the pin, but you will still need to press on it in order to put the cross pin back in with a new washer.

Go aftermarket for the washers. The oem ones are junk. DTE sells them. They sell stronger clutches too. Depending on how long the washers lasted before they cracked, you may be able to re-use the clutches. just make sure to keep them in order.

As long as you dont replace the gears or bearings, you don't need to re-shim or adjust for backlash.

Bill Curlee

I agree!!

The clutches and belleville washers should be inspected and changed. Very common for them to crack and damage the rear.

Here are some very enlighting post that you should read and then you can decide what you want to do with your differential.

I up-grader my rear last spring and it worked out very well. :

- C5, ragtopws6 , Upgrading your C5 rear with C6 Z06 guts, : http://forums.corvetteforum.com/c5-g...-z06-guts.html
-

- C5, Its_Go_Time, Output Shaft Install - Left and Right: http://forums.corvetteforum.com/c5-t...post1573407966

- C5 Differential Seal replacement: http://forums.corvetteforum.com/c5-g...on-photos.html

RonSSNova

Don't do it! The extra accelleration will injure your back and put other drivers at risk........

Put a high quality converter in it while you're in there. Yank, Circle D, etc. 3200 would be good if you aren't a racer. You will love it.

I did the shaft upgrade, but again, if you don't put sticky tires on it, probably not necessary.

Clutches were toast in mine, the bellville springs busted.
I did not need bearings. My unit had 140K on it.

I found it to be a fun job, no special tools required except for an arbor press.

Ron

Patches

Don't forget to transfer the adaper plate from the 2.73 diff to the 3.42 diff. This is only on A4's.

I did this swap as part of a larger upgrade a few years ago and posted this thread illustrating it.

http://forums.corvetteforum.com/c5-g...mega-pics.html

SJC5

Excellent advice and suggestions from all!

I'm waiting on a couple of estimates from local reputable Corvette shops now.

Thanks again

SJC5

HELP!!!

I may have a problem! I took the left side differential cover off to check the magnet.

...and found this shiny piece of metal, polished on both sides, almost a slight radius on it, and about .025 - .035 thick.

Where did it come from???

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SJC5

I pulled both side covers off to examine the bearings and race surfaces. No defects found.
Could the pieces be from the shims or something out of the clutch packs?

SaberD

looks like pieces of the belleville washer. I'd say there is a good chance this diff had a whine in it. when something like that gets caught in the teeth of the gears, it deforms the carrier, and the gear backlash and bearing preload need to be readjusted.

RonSSNova

That's pretty black inside. I think you should follow the proceedure posted by Bill Curlee and go through it. It really isn't hard, and not all that expensive to replace shafts, clutces and springs. You will be glad you did down the road.
As long as you don't remove the bearing races from the covers, and mark the case and the pinion support so it goes back in the same way, there are no setup issues to deal with. You just put it back together. I think you are going to have to trust the sellers word on any whine.

Ron

Bill Curlee

I agree!!!! I was very surprised at how BLACK the interior of the diff was!!! Either the diff wasn't properly serviced OR it was severly overheated. Ive NEVER seen one that nasty.

If you are going to keep it,, it needs a very good cleaning with BRAKE PARTS CLEANER and the entire clutch pack and hardware will almost definitely need to be replaced!

If you skimp on this step, I can almost guarantee, you will have the unit back out in short order.

How close are you with the seller????????? I do NOT think your are getting the entire true story on this unit!!

SaberD

I agree with Ron. I would see if it whines first before doing anything with the shims.

Mineral spirits mixed with ATF in a spray bottle will also clean it up pretty nicely. could probably use a good spray out with the hose first.

SJC5

Thanks Saber, Ron, and Bill!

Jeremy@RPM believes its from the Belleville Washers as well. I'm waiting to hear back from him for an estimate to R&R both Clutch Packs and associated bearings. I hope it doesn't drain my wallet too bad. The wife is already pissed at me for wanting to do this swap.

I also need to clean the insides. Thanks for the tip on using mineral spirits and tranny fluid.

Bill Curlee

Would love to have pictures of the carnage. See if they will snap a few for us.

Good luck with the rebuild and let us know when you are ready to reinstall..

Bill

kh400

I agree with Bill, but I believe the unit is toast. I would ask for my money back. Looks to me like it ran out of oil and got very hot. I'll bet the ring and pinion have "moved metal" which signals junk!!!!! Sorry for the bad news, but at the very least, if you decide to keep it, disassemble the unit completely and inspect closely and replace all the bearings and ring and pinion and rebuild the diff. Big money. Good luck!!!!

SJC5

Thanks and I hear ya but when I took a good look inside, no signs of heat damage on any gears, bearings, and bearing races. I think the gear oil was never ever changed.

Anyhoo, it's in the shop now for a good thorough inspection and rebuild, where necessary. For sure, new HD Clutch Packs are going in. Maybe some bearings. Parts are coming from RPM.

Bill Curlee

Well,,,,,,,,,,,,,,,,,,,,,,, With all the advice and your decision to keeep it,,,,,, PLEASE,,, let us know how it turns out and what all it needed to be replaced to restore it to new.

It will help us understand the stroy on what was observed.

Bill

SJC5

Bill,

It's in the shop now. Should have some news in the next week or so. I'll post a follow up when I get the information.

My background...
I work in manufacturing for more than 35 years now.

• 8 years - tool maker
• 12 years - tool & die maker
• 2 years - tooling manager
• 10 years - tool engineering manager (It was time to tell the engineers how it's really made in the shop - integrated mfg techniques with engineering)
• 3 years - manufacturing technical analyst (current)

I know quite a bit about machining, heat treating alloy steel and tool steel, hardness threshold for machining heat treated steels, and precision assembly.

I'm relying on my training and experience to help me make my decisions but there again, I don't pretend I know everything. I use a lot of luck in my judgement as well.

Thanks to everyone for all the advice I get here too. There's always room for me to learn more.
.