rear end rebuild.

[tscott9330]

Alright the frame is painted and now it's time to start puting her back together. I want to overhaul the rear diff., but i cant seem to figure out what it is. Jegs lists the rebuild kit as just a corvette 68-82 but doesn't mention any other designation. Is it a 10 bolt, 12 bolt or what? when I rebuild I also want to install a 3.7 or so rear end to give the old girl a bit more pep. any help would be greatly appreciated.

Thanks Tom

P.s. Also I would like to know how good the stock limited slip is. If I stomp on it does one wheel spin and the other do nothing or what?

Thanks again

 

[72Mako]

Tom, I've tackled a lot of stuff on my '72 including rebuilding the muncie and trailing arms. But I felt that rebuilding the rear diff was a bit beyond my abilities. After talking with Bairs at Bloomington Gold and viewing their free video on how they rebuild rear diffs, I decided to go with them. They did a quality rebuild and I now have a number of trouble free miles on it including a number of drag sessions. I reused my original gears as they determined that they were in good shape. I also had them put in the yokes with the hardened tool inserts as mine were worn down- a common problem. I got back my original date coded unit as I requested. Since you are considering a gear change, you might consider this route as setting up new gears is sort of a black art. But if you have the abilities, you certainly save some money doing it your self. Charles

 

[JohnZ]

Forget Jeg's - they don't know Corvettes. If you haven't set up a Corvette rear end before and don't have the special tools required, send it to Bair's or Van Steel - they do it every day. The OEM Posi unit is an Eaton, and it will need to be rebuilt as well.

 

[tscott9330]

Ok, thats not the answer i was expecting. Let me rephrase the question, I am going to rebuild my rearend myself, what ring and pinion gear do I need and what special tools will be required? I know ecklers sells a rebuild kit, but I cant seem to find a reduild for the posi. I am in this project to learn all I can and I want to know how to do this, so any help anyone could give me would be greatly appreciated.

Tom

 

[GTR1999]

You can rebuild it yourself,you have the right attitude. too many people are afraid to touch their cars when they can do a lot of other things. Guys do body offs and engine rebuilding but then send out the rear bearing and differential jobs?

The 63-79 vette rear is a 10 bolt Eaton unit. Posi was optional until 1970 then standard feature.

If you replace the the gears use the best available,which is now made by US Gear sold through Tom's Differentials In CA. They sell a 3:73 which you're not going to notice the difference between the GM 3:70 ratio. I used it and it's a good setup with just about any tranny you have.

Buy the rebuilt kit from Bairs or Randy's. The posi clutches are still sold by Eaton through their distributors,Tom's is one. Shop around and you should get the kit for about $95-100 and the posi $80. You can setup the posi according to the GM overhaul manual or custom shim them according to Tom's. If you follow Tom's procedure then buy their posi shim kit too,about $25?

Drain the rear and mount it on an engine a stand,it's much easier to work on this way. Follow the GM overhaul manual again. I don't use a pinion depth tool,you can set the gears by pattern.

So what special tools do I use:
1/2 socket set
bushing drivers
2 jaw puller
0-30in/lb dial torque wrench-maybe you can rent or borrow one?
0-100 ft/lb torque wrench
1/2" impact gun
20 ton press
die grinder or Dremal tool
file
small pry bar
combo wrenches
1" dial indicator w mag base
1" micrometer
snap ring pliers
1/4" NPT tap if you want to put in a drain plug,I always do on my cars.
If you have most of these tools you can do it. If you don't then you might want to consider sending them out. You will also use them torebuild the steering box,rear bearings,transmission,etc so they're a good investment. BUY good tools,not the imported crap.

Not including my time the parts with rebuilt hardend yokes run me about $550-600.

Hope this helps but if not let me know.

 

[tscott9330]

Thnak you coupman, I appreciate the info. I have 90% of the tools required and need to buy the rest to rebuild the engine anyways. i agree with you that many people have a strange fear of certain parts of the car. I believe that the only way to be comfortable around these kind of cars is to know every bolt in them.

I appreciate the detailed run down and the supplier names.

If anyone else has any helpful hint to save on time or money I am always up to try something once


Tom

 

[GTR1999]

Any time Tom, I can scan soem pictures for you too if you want. I have just completed a 72 diff with new 3:08's and have a 78 on the stand that's been trashed. Let me have your email and I'll pop these out to you.

 

[phungus]

I have a question since we're on the subject.

What is a good upgrade to beef up the rear-end on a '75? I'm going to be pushing 600+HP with my blown engine soon, and I'm 99% sure the rear-end in my Vette is stock and original. I seem to recall Tom had some upgrades for them? I'm going to be replacing the U-Joints with the non-serviceable Spicers, adding dragvette 1/2-shaft loops and 6-link kit. If I determine that the side-yokes or the diff itself is not up to par, what should I be upgrading to?

Can you slide a beefier unit inside there?

I would not be doing the work myself, unless the shims were pre-set and the pattern was setup right. I learned not to work on diffs when I had my Jeep.

I'm beefing up a TH-400 to work so at least I won't have a stick to shock the drivetrain as much.

 

[GTR1999]

Tom's can custom fit a 12 bolt Eaton carrier in a vette housing,They have been doing that for 30 years that I know of. The guy that started the trick sold the business to Tom years ago. I actually have a pretty good procedure guide line for doing this retro-fit but I neve have. For the power you're talking about,you want the best you can get there. Cold stabilized yokes and posi gears,10-17 posi gears,steel bearing caps with 1/2-13 SHCS bolts, radius the carrier,tune it to work without the 4 Eaton posi springs,HD rear cover,maybe the HD 1/2 shafts. The best thing to do is call Zeus at Tom's and go over it with them. If you have access to a good machine shop then you can build it yourself. If not be prepared for about $2500-$3,000 to build one of these rear ends.
With the HP you have then, a 34 element sprag wouldbe needed in the TH400 too.

 

[phungus]

Tom's can custom fit a 12 bolt Eaton carrier in a vette housing,They have been doing that for 30 years that I know of. The guy that started the trick sold the business to Tom years ago. I actually have a pretty good procedure guide line for doing this retro-fit but I neve have. For the power you're talking about,you want the best you can get there. Cold stabilized yokes and posi gears,10-17 posi gears,steel bearing caps with 1/2-13 SHCS bolts, radius the carrier,tune it to work without the 4 Eaton posi springs,HD rear cover,maybe the HD 1/2 shafts. The best thing to do is call Zeus at Tom's and go over it with them. If you have access to a good machine shop then you can build it yourself. If not be prepared for about $2500-$3,000 to build one of these rear ends.
With the HP you have then, a 34 element sprag wouldbe needed in the TH400 too.

Whoah holy crap I didn't know it was going to be that high. That's like almost as much as it would be to custom fit a Ford 9 inch in there.

Man, I didn't know they were THAT bad off....

Jeff

 

[tscott9330]

Coupman I appreciate thje offer for a little help with a few pics.

My email is Tscott9330@aol.com

Thanks
Tom

 

[GTR1999]

Tom I'll get some out to you right away. 5:00 pm est 2/11

 

[Gary]

Rear end rebuild

I am replacing the side yoke seals in my '69 vette. I have a few questions; are there any tricks to installing the small pin/bolt that holds the larger pin; is there a torque spec when tightening the small bolt, and do I need to use a locktite on the small bolt? Also, I think the torque spec for the rear cover is 40 -50 ft/lbs, is this correct?
Sorry, I don't know the correct terminology for the pins/bolt.

Thanks,
Gary

 

[GTR1999]

Gary
I don't remove the cross shaft or bolt if only removing the yokes. A good pair of 90* snap ring pliers work. I have an old set I got 35 years ago and they work great. With the yokes out you can pry out the old seals and replace- use National or CR only. I think CR are the best.

The rear cover bolts I torque to 55 ft/lb or 60 if using socket heads on the HP jobs.

 

[Gary]

rear end rebuild

GTR1999, thanks for your reply. I have already pulled the cross shaft and replaced the seals. Do you know the torque spec on the small bolt, and should I use locktite?

Thanks,
Gary

 

[Gary]

rear end rebuild

GTR1999, thanks for your reply. I have already pulled the cross shaft and replaced the seals. Do you know the torque spec on the small bolt, and should I use locktite?

Thanks,
Gary

Gary, I have the same questions regarding the small bolt's torque and use loctite or not. Did you ever find out?

Thanks in advance, Gary also!

 

[GTR1999]

Those are 1/4 -20 threads so I don't jump on them with a TW. I use 242 blue and tighten them by hand. The original bolts are pretty good and have 4 lines on them, some of the new ones are plain and I twisted & almost sheared one once, that was enough for me.

 

[Gary]

rear end rebuild

When I removed the small bolt, there appeared to be no lock-tite or a lock washer. I was thinking with the rotating centrifugal force, I think the small bolt will not loosen whether I use lock-tite or not. What do you mean by 4 lines on them?

Thanks, Gary

 

[GTR1999]

They have 4 lines on the face of the bolt, just like any bolt rating. There should be an internal star washer on the bolt. They didn't come with loctite orignally, but a drop of the 242 won't hurt it.