Point number one. I live in Belgium. So having cores and diff shipped transatlantic is going to be prohibitive. Best to DIM if I can.

I have no complaints about diff. It operates fine. However, my backlash is excessive at 0.017

Contact pattern looks fine. End play of stubs looks fine.

As I understand, the carrier needs to scoot from left to right (when looking at the pinion) to reduce the backlash.

My question is, what would you good folks recommend that I order to address the backlash issue but also do a few things to freshen up - without going into pressing bearings off, crushing new sleeves and measuring drag torque ?

MTIADC3

 

Super cooooool. I found a guy here willing to help me rebuild it with him !!

So I’ll go for a full rebuild.

One question. How can one tell if ring and pinion needs to be replaced? What should I be looking for ?

 

Check in on this forum with Gary or GTR1999. He is the go to guy for differential and trailing arm bearing information. I would start by searching his posts for information. They are all a good read. Jerry

 

What are readings around the gear? What is variance?
those axles look great.
might as well tune and polish you will need shims to adjust i think..
Gary and others helped me here..
https://www.corvetteforum.com/forums...-advice-5.html

 

How many miles (kilometers) do you expect to put on it in the next 10-15 years? If you have no complaints and it operates fine, why open Pandora’s Box now?

If you alter the position of the carrier, you will change the contact pattern. That may risk introduction of a gear whine. Just moving the carrier alone may result in a less desireable pattern unless you also change the position of the pinion.

Unless there is obvious damage and/or the unit howls like a banshee, no real reason why the ring and pinion need to be replaced. From the pictures, yours look fine.

If it were my unit, I would:

1. Very carefully examine the posi case for cracks. Thoroughly clean out all the fluid, then spray small areas of the posi case with a highly evaporative solvent like Brakekleen and look for any evidence of cracks.

2. Remove the ring gear bolts one at a time and reinstall with red thread locker and torque to spec.

3. Replace the pinion seal with a SKF 17190. Read up on how to do this to avoid affecting the pinion bearing preloads. It is fairly straightforward to do with the differential removed.

4. Replace the yoke seals.

5. Fill with Lucas 85w140 and 2 bottles of Delco 10-4003 additive.

6. Although you state your axle play is fine, what is it, exactly? You might want to check the Rockwell hardness of the tips just to be sure you know what you have.

If you are dead-set on restoring the lash, then you’ll want to get a replacement crush sleeve and a set of super side shims and some pattern paint and read up on how to obtain a pattern that is compatible for a used set of gears. GTR1999 has some excellent posts and recommendations on what he does for those situations.

 

Thanks @69L88 for this write up. This makes sense to me. I don’t really see any issue that warrants a rebuild and am not inclined to risk a whine. No Pandora’s box for me. Been there. Done that.

I will inspect super carefully, just to be sure.

I read up on replacing the seal and, on a bench, it is so straightforward it would be silly not to do this.

The stub axle end play is at 0.017 on both sides.

incidentally, this car sees about 2-3000 miles on a good year.

Thanks a million !

D.

 

Pinion seal leaks are the #1 issue.
Replace that and put sealer in the right places to prevent leaks.
GTR1999 has great threads to show how to do this.
Leak test it on an engine stand to be sure.
If it does not make noise, do not change any of the shims.
If you do, it might.
Cracks seem to be the #1 breakage issue, so the suggestion to check for them is extremely valid.
If you are not going to change the bearings, then why even dissasemble it.
Just change the seals.
But I do also like the bolt threadlocker idea.

Recommended Side bearings and seals.

 

Thanks for feedback. Just to be clear, are you suggesting I do just the seals and clean everything out; not replace the side bearings as risky ?

 

Once you pull the stub axles and carefully remove the side seals, you can inspect the roller bearings supporting the stub axles. Given everything else you have shown, I strongly suspect they will be fine. Keep the lid on Pandora’s Box closed!!!!

 

Copy

 

Tools that help are inch torque wrench and plate..

specs for used bearing in thread..good to check prior to tear down..

i would still tune it and remove springs..and polish case while its out for inspection..label everything!!!

 

If it rolled well, spins well, no noises, didn't leak excessively, etc. IIRC you are not planning 400+ HP, I would not even remove the posi housing, bolts, shims, any of it.
If it doesn't make noise, it ain't broke, why "fix" it? Why risk messing with the backlash settings & gear pattern?
The gears have been run with those settings, and now have a wear pattern, if you change them, you could very likely get a whining rear.
Just do the 3 seals 'cause they are well known to leak.
Make TRIPLE sure you don't get any dirt inside.
Brakeclean on the posi housing surface looking for cracks. 'cause it evaporates quickly.
If you use the dial version of the inch -pound torque wrench, and measure it before you take the pinion nut off, and ink mark it, and re-do it to that number, you can likely reset it and replace the pinion seal without needing a new crush collar and all the total dissasembly that goes along with that.
Now if the numbers are way off, contact Gary for assistance.

You will still need all the tools in Interpon's pics above to do the pinion seal.
That pinion nut is a *****!

 

Found it !!

https://www.corvetteforum.com/forums...-pictures.html

 

you have a diff in good shape. It appears to be a early 70's one. The posi case is not the later 71-79, that I can see anyway.

The lash is loose at 017" the axle endplay is also 017"? If that is correct, then they are probably good.

How you approach it is up to you, depending on time, skill set, tools, etc.

Since you have it out you can do some basic things like the seals and cover gasket. The lash can be adjusted but you need to understand the way it works and what preload you end up with, along with the lash. I would set the lash to 006-008", the pinion depth will stay the same since you don't need to replace the pinion shim.

I would also change the RG bolts to ARP's, if not I would remove one at a time, clean the hole and loctite the bolt in place.

Mission creep is easy with one of these.

Since you have the axles out for new seals, I would get them checked for hardness on the face and measure the face dimension to snap ring. That will tell you a lot.

You can also tap a drain hole in the bottom of the housing and catch the chips.

 

That's the one!
Sometimes less is more!

 

Replaced my ring and pinon gears with a new ratio set....thought I did everything right but only took two months before I broke a tooth off. I too recommend letting sleeping dogs lie...especially if you do not hear any howling going on.

 

What brand of gears did you use and how did you drive the car?

 

Thank you gentlemen This has been tremendously helpful.

I do plan to let sleeping dogs lie, as I am concerned that if I tighten the backlash, I will get a whine despite a perfect execution of the task. For the moment, other than the "clunk" I get when dropping into reverse/first, the posi works just fine. It doesn't even leak. However, preventively I do plan to replace the seals, replace the ring gear bolts with ARP + loctite, clean out meticulously the case, add fresh fluid and be done with it

Correct !

To see it it is possible to tighten with another snap ring ?


D

 

If you are going to use ARP bolts, you will need to make a relief chamfer cut on the posi case holes as the ARP bolts have a radius under the head. Absent the chamfer, the ARP bolt head will not contact the case, resulting in an unacceptable condition.

Unless you are very careful while you install the chamfer, you will risk getting metal contamination.

In your situation, I would recommend you reinstall the current bolts with red thread locker and torque to spec.

Relief chamfer

ARP bolt head flush to case

 

To be clear, 017" axle endplay in a stock or common rebuilt diff is good. 017" backlash is loose.

L88's pictures of the countersunk holes is important and must be done, I didn't go into the detail on it, but it is required since ARP RG bolts have a small radius under the head for strength. Always check the seating with a 001" feeler, it shouldn't slide under the head.

The snap rings for the axles are typically 066" thick. They are not a common ring to find locally here, not sure there. I have a large assortment of them I have collected over the years ranging from 055 (too thin) to 066". They can make small adjustments but you won't get them to cut the endplay down to 005-007", that would be much more involved and not necessarily what you need to do.