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OK, this is the first of several Digital Corvette Forum Picture Posts.

This is a 1971 LT1 Diff a local guy brought in to me to check for him last winter.

This car was just purchased and he was told no one worked on the diff to their knowledge. I checked the side yoke play. .020-.025" was found but the play was in the sloppy stock posi not yoke wear. This will be discussed in another post or two so you'll just have to wait!:smack What I did was to mount the diff on my engine stand and put some gear oil it. After 5-6 hours I noticed a leak at the pinion seal and proceeded to replace it.


Here is the diff sitting on the stand with oil in it. I do this with every rebuild as well just to be sure. I let them sit 24-48 hours sometimes more.


Here is the close up.




Before tearing it apart you want to know where the reference points are. If doing this in the car you need to mark the pinion yoke,nut, and pinion end so that they all go back together in the same relationship to maintain the bearing preload. Since I have it out it is much easier to get a precise reading of drag with my 0-30 in/lb dial wrench. Used bearings should spin smooth and have about 5 in/lbs of drag.





I found someone was into this before. The witness marks were there and I heard the replacement seal hitting the yoke shield when I turned it by hand.



I use a puller to remove the yoke, this is one my friend Tom Buddy clued me in on years ago. Works great on these and rebuilding a diff when you have to pull the pinion off a lot during setup.




You want to look over the parts when you remove them. Here is the seal the previous mechanic installed.You have to look at the gap between the flange and housing. Usually it's about .125" but that can vary. Hitting it home will distort it and leaving too high the yoke will hit the flange as on this one.





You can see where the seal flange hit the yoke.



Also the last guy was clueless installing the seal. Here are the pinion yoke splines- no sealer. Oil will wick up and out if installed like this.



Here is the yoke. Look at the OD where it mates with the seal. If there is wear there you need to buy those expensive speedy sleeves or you'll have a leak.


Unlike some places my goal is not to sell parts or services. Instead of telling the guy the yoke was NG I cleaned it up and checked it on our scope. This one didn't need the sleeve.



Here's the new CR seal. Spend the extra couple of bucks and buy the best parts. Not all seals are the same and I have seen some rebuild kits on the market with the cheapest junk you can find. This is a CR/SKF seal.


Here is the secret to stopping a future leak- good old #2 on the splines. A few bucks for the right stuff saves you a lot of swearing in a few weeks!:spanked:







Back together, torqued and ready for the leak test.



24 hours later dry as the moment I installed it.



I reused the yokes with 90k miles on them, replaced the seal, installed Lucas 85-140 gear oil and GM additive, Back to the owner.

This is the type of post I usually do. What is your feedback?

Gary
 

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as always, good stuff Gary. I went ahead and stuck it for you. :thumbsup:
 

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Excellent as usual Gary. Your posts are very informative.
 

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These are the type of posts that helped me go through my rearend last rear. Great job, Gary - nicely detailed and very informative. :thumbsup:
 

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3 MINUTES

Got to be a record for the FASTEST sticky!!:laughing:
 

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as always, good stuff Gary. I went ahead and stuck it for you. :thumbsup:
Thanks Jason! :thumbsup:

You beat me to it! :cheers:
 

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For anyone changing the seal in the car I find it almost impossible to drive the new seal into place in the tight confinements of the drive shaft tunnel.
After a flustrating attempt I made a in car seal replacement tool.
As you can see I used a piece of exhuast pipe adapter and cut it down so it fit perfectly inside the lip of the seal. I welded a plate to the top of this adapter and then welded a 2 foot length of pipe to this plate.
I can install a seal in a few minutes without the flustration of starting the seal and trying to tap around it's perimeter.
Just hold the seal in place, install the tool and a few hits with a big hammer drive it into place effortlessly.
I have loaned this tool out to a few guys doing this change and they all find it extremely easy.
 

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Very good work as usual Gary. I know mine is leaking and needs replacement. I guess I will get after this one this winter. When I pull my yoke if it is sealed with sealer like you mention, what it the best way to clean the yokes splines to get the old sealer out?
 

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Discussion Starter #11
Very good work as usual Gary. I know mine is leaking and needs replacement. I guess I will get after this one this winter. When I pull my yoke if it is sealed with sealer like you mention, what it the best way to clean the yokes splines to get the old sealer out?
Eddie,
I use a scribe that Sears sells. It is long and one end has 90* tip. Workg great to scrape the old junk out- if there is any. A smal wire wheel works good too.
 

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For anyone changing the seal in the car I find it almost impossible to drive the new seal into place in the tight confinements of the drive shaft tunnel.
After a flustrating attempt I made a in car seal replacement tool.
As you can see I used a piece of exhuast pipe adapter and cut it down so it fit perfectly inside the lip of the seal. I welded a plate to the top of this adapter and then welded a 2 foot length of pipe to this plate.
I can install a seal in a few minutes without the flustration of starting the seal and trying to tap around it's perimeter.
Just hold the seal in place, install the tool and a few hits with a big hammer drive it into place effortlessly.
I have loaned this tool out to a few guys doing this change and they all find it extremely easy.
If I dont have access to a welder can anyone think of a similar tool? Im not familiar enough with the job to know what will work and what wont.
 

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Gary,
Thanks for providing me this info. Exactly what I needed.
For clarity's sake, once I install the seal do I just run the nut back down until I get to my original pre-disassembly torque reading?
Again, thank you so much for providing us with the technical write-ups!
Much appreciated
 

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Discussion Starter #16
If you are doing the job on the car then I think the best you're going to get is back to the witness mark you made. If off the car like this one then I go back rotational drag with my in/lb TW. Used bearings should be about 5 in/lbs.
If you do have it out of the car pull the cover and check the other things as well.

Howard,
You don't want to move here, a little state between NY & Boston and one of the most expensive places to live. Cost of living is too high here and the mfg jobs are just about gone. I'm going the way of a trolley car mechanic!!!!~obsolete. :laughing:
 

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If you are doing the job on the car then I think the best you're going to get is back to the witness mark you made. If off the car like this one then I go back rotational drag with my in/lb TW. Used bearings should be about 5 in/lbs.
If you do have it out of the car pull the cover and check the other things as well.

Howard,
You don't want to move here, a little state between NY & Boston and one of the most expensive places to live. Cost of living is too high here and the mfg jobs are just about gone. I'm going the way of a trolley car mechanic!!!!~obsolete. :laughing:
Gary...did you say 5in/lbs for used bearings? That sounds kinda loose....forgive me master for I do not know what I speak of:laughing:
 

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Discussion Starter #19 (Edited)
Hi Guys
I guess a lot of you have been working on leaking pinion seals this winter because I have been emailed and called about installing them and I also have seen threads on various forums about it.

Now I think this thread should really walk you through the job but to recap some of the questions I was asked recently I will post them here. There is NO SECRET with this job, qualified mechanics with a car on a lift and tools can do this in short order. I prefer to have the diff out but it can be done on the car. You will have to get the yoke held in place with a tool or even Large pipe wrench.

Ok Questions

1- What is the depth of the seal, should it have a gap?

This does vary from housing to housing. With the exception of some mid 70's housings that were not bored deep enough, the seals usually will have a gap. Now the old manuals did reference about an 1/8" gap but I always measure the bore depth. They may sit flush or have a gap, it doesn't mean the seal is at fault.

2- What brand seal should I get?

My opinion is the USA made CR/SKF brand is the best out there. The seals I see in some kits are similar to CR but I did have one rip and never used one again. They should be about 1/2" thick, some of the junk I see were blue and thinner. National isn't a bad seal.

3- Where can I buy the seals?

If you want the ones I use I can supply you with them or just go to NAPA and they were stocking CR under the NAPA brand. You will probably pay a little more but maybe not. The CR number is 17190 about $12 each.

4- How to install in the housing?

With the diff out I just use a hammer and tap it in evenly. I let the weight of the hammer seat the seal and tap it on the inner radius. When it's home it will stop and you will feel the difference. STOP there or you will distort the seal and it will leak. Doing this on the car is not the same because you won't get the same feel but it will stop the same.

5- Do I have to replace the outer bearing or crush sleeve?

Unless there was an issue you should not have to as long as you don't over-crush the sleeve installing the yoke back. Crush sleeves will not make it out past the outer race so that would mean tearing into the diff and removing the posi case- something you don't want to do if you have not worked on a diff before. If you have a solid sleeve like I fit then it will come out the outer bore.

6- How tight do I set the nut to?

Here some believe you are looking for a ft/lb rating, which if you have a solid sleeve you are. With a stock crush sleeve you are not, you want to dial it in with a 0-30 in/lb TW like I show above. If you don't have that or are doing this in the car then make witness marks before you start,again like I show above. Used bearings I set to 5-7 new bearings 18-20 in/lb.

7- Should I use a new pinion nut?

Not really, if you are using the witness mark method then you have to reuse the original locking nut. when I rebuild a diff I always fit a new nut but you can use yours. Clean it and use brake cleaner on the threads of both the nut and pinion. Then use Loctite #271 RED threadlocker and stake the nut when done.

8- What about the pinion yoke?

Check the yoke OD where the seal sits. Use some scotchbrite to polish the OD and see if there is a wear groove in it. IF so then I use the Speedy Sleeve. These are expensive and not stocked at many places. IF there is no groove then I always measure the seal, bore and yoke to be sure there is clearance under the yoke shield and seal flange. USE Permashield OR #2 Permatex sealant on the yoke splines and RTV on the seal OD.

I think that covers the questions I was recently asked, if you follow these and still have questions let me know. Out of the car it's not a hard job as long as you have the correct tools.
The CR seal is all I use and have for years.:thumbsup:
 
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