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Discussion Starter · #1 ·
My '74 diff was totally rebuilt 10 years ago when I did a complete frame off resto and now has approx 7,000 miles on it.

Now that spring is around the corner, I started doing some of the little projects before I return her to the road (checking for loose bolts, touching up the painted calipers, adjusting parking brake) and I found that there is alot of endplay between the rear wheels and the diff and I know that its all between the yokes and the "C" clip that holds the yoke in place. I have to assume that maybe the rebuilder didn't believe in shimming this tigher. (don't belive their is a failure happening do to how smooth it seems to operate)

MY QUESTION: If I remove the rear cover and find no metal particals, Can I simply buy a shim kit and install them with simple hand tools? I do not own any dial calipers or bearing press. I have never seen anybody remove a yoke from a Corvette diff (but doesn't look too tough), am I right? (Keep in mind, my diff should be still brand new on the inside, I had the builder change out the ring and pinion and new spool)or should I drive my car to my local speed shop (very good with Corvetts) and pay them to do it. I would like to try it myself ( to learn) plus get the satifaction I did it myself. On my frame off I did all the dis-assembly and re-assembly by myself except I jobed out all the machine shop work AKA diff, trailing arms. A-arms motor and trans.
 

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well since no one else responded I can answer your question.

Can you remove the diff and use basic tool to shim the axles(yokes)? Yes you can, is it the right way to go- no not in my opinion. You will need 90* snap ring pliers to remove the axles. Some "rebuilders" do shim the yokes at the snap ring ( C-clips are not used in vettes diff's unless it's a Tom's 30 spline axle).

The problem most likely is not with the axles unless they are undersize. Were they replaced at rebuild or kept? Some rebuilt axles have issues,most are good. New ones I believe are imported these days.

If you decide to dig into this you first need to check the axles to see how much is worn away from the face. Look over my threads, I cover this.

If the axles are good then the play is in the posi setup and or the cross shaft hole. Getting into this is really not for the first timer unless you have some guidence and more then hand tools. I use die grinders,belt sanders, lathe and surface grinder when I set them up. Most won't have this machinery and so you'll get the basic factory setup. Now not to discourage you since you may in fact do a better job then a shop that pops them out in 5 hours, but you're have to do your homework and really decide if that is what you want to do.

Are you using the plates and springs or tuning the posi without them like I do? IMO, the springs are a band-aid for production builds and what I suspect you got. The keep constant tension on the side gears and clutches but will not correct improper spider setup. This is the reason these hammer a lot, improper setup with the springs loading them. Again look over my threads on diff's.

If the axles are still good, a correct tuned posi will often require grinding the face a few thousands to setup the endplay to 005-007"

So I would measure the exact endplay you have, do it in the car. Pull the 1/2 shafts if needed, get an indicator and see what you have. If under 050 and no other issues, then drive the car. If over 050 then consider correcting it but do it the right way.:thumbsup:
 

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Discussion Starter · #3 ·
well since no one else responded I can answer your question.

Can you remove the diff and use basic tool to shim the axles(yokes)? Yes you can, is it the right way to go- no not in my opinion. You will need 90* snap ring pliers to remove the axles. Some "rebuilders" do shim the yokes at the snap ring ( C-clips are not used in vettes diff's unless it's a Tom's 30 spline axle).

The problem most likely is not with the axles unless they are undersize. Were they replaced at rebuild or kept? Some rebuilt axles have issues,most are good. New ones I believe are imported these days.

If you decide to dig into this you first need to check the axles to see how much is worn away from the face. Look over my threads, I cover this.

If the axles are good then the play is in the posi setup and or the cross shaft hole. Getting into this is really not for the first timer unless you have some guidence and more then hand tools. I use die grinders,belt sanders, lathe and surface grinder when I set them up. Most won't have this machinery and so you'll get the basic factory setup. Now not to discourage you since you may in fact do a better job then a shop that pops them out in 5 hours, but you're have to do your homework and really decide if that is what you want to do.

Are you using the plates and springs or tuning the posi without them like I do? IMO, the springs are a band-aid for production builds and what I suspect you got. The keep constant tension on the side gears and clutches but will not correct improper spider setup. This is the reason these hammer a lot, improper setup with the springs loading them. Again look over my threads on diff's.

If the axles are still good, a correct tuned posi will often require grinding the face a few thousands to setup the endplay to 005-007"

So I would measure the exact endplay you have, do it in the car. Pull the 1/2 shafts if needed, get an indicator and see what you have. If under 050 and no other issues, then drive the car. If over 050 then consider correcting it but do it the right way.:thumbsup:
Thank you for the info. I had the diff rebuild buy a Corvette restoration shop (I thought was very repitable) I went to him hoping my rebuild for the diff and trailings arms and steering gear box would be done correctly and be woory free for the rest of the years i own this car. (I have owned this since '86 and have only put on 23,000 miles)

Looking thru my paprer work they replaced the ring and pinion (changed it to a 355) replaced the posi unit and new rear cover. Yokes and case are reused. The chassis has 114,000 miles on it (7,000 since restoration) If I am following you correctly my case maybe worn or the posi is not set up correctly. I cannot tell you if the endplay was there when i re-installed the unit or if it happen now. but its is alot more than 0.050". Any Idea of how much shop time it would take to fix (a new speed shop has open near here since I build my car and they set up alot of Corvettes to race at Road America. My wife has me a a limited budget if you get my drift:D
 

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a new speed shop has open near here since I build my car and they set up alot of Corvettes to race at Road America.
what speed shop in Northern Wisconsin sets up Corvettes to race at Road America? as you can see by my avatar I have more than just a passing interest?
 

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Or the cirrclip/s have come off. had that happen to my 79 and also found another in amoungst the pinion bearings playing hell with the bearings :spanked:
 

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Are you gonna beat the snot out of this thing or just cruise it?

My thoughts- if it's a cruiser, run it. Fix the other 5 problems that arise once you've put 150 miles on it. That'll keep you busy all summer.

Next fall is the time to take it down for something like diff work. Especially diff work that's a borderline call like this one. Have fun with it!
 

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I don't know the shop you used but since they replaced the posi case then I be concerned, not as much for failure more on setup.

What I've seen and read online is it's very common to sell someone a new loaded Eaton posi. Now using one can be debated among rebuilders as to if it's the best option, I don't think so unless getting the job done fast and an increased profit margin is important. I don't usually use them, I don't like the way they're set up. I did just work with one. It was in the diff that lasted 800 miles built by a place in TX. Before I took it apart I measured the play in the side gears without the springs, 030" which is totally unacceptable. I wonder how many check them out of the box before loading into a customers diff?

Unless you know for certain if a new loaded case was used, new bare case built,or a good used case built them it's hard to say if that is all or part of the problem. I have also seen used parts sold to guys that were clearly worn out. I've tossed out better parts then some I've seen sold. That's another story though.

If you have more then 050 and can drop the diff out at home then I would. There is a confusion on the type of retainer used on the axles. They are a snap ring, about 060 thick and installed with snap ring pliers. They are not the stronger C-clips used on the common GM axles.

If you get the cover off and oil drained post some pictures or give me a call and I'll go over it with you.
 

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PS, I'm rebuilding the complete IRS off a '66 BB now. This car was NEVER apart and I just finished the posi polishing & tuning. The original yokes are perfect and in fact I will be grinding about 005 off them to set to 005-007". This is the way they should be and were up until about 1973. Many times I've been able to reuse the C2 and early C3 yokes over like this. Yes they do wear but not as much as the 73-79 did. Look at the face of yours if you remove them, if they have a center drilled hole they're originals, if there is a blank face they're rebuilt. If the parting seam on a rebuilt is about 1/2 way down on the spline you better replace them as those are the ones I've seen shear in 1/2 under load. I haven't a lot of them but look up the diff I did for Curby here and you'll see what I mean. Pretty bad work there with those rebuilts.



 

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Discussion Starter · #12 ·
Sorry for the long delay. Been too busy to find time to re-visit my Corvettes Dif.

I finally found the time to borrow a dial indicator and afix it to my chassis and measure the end play of the yokes. They are both at .045

Should I leave it as it is, or should I allow a speed shop to install shims between the yoke and case? I know the correct way is to buy new yokes but for the little I drive this car just wondering if I could save some cash


On another note. My Trailing arms are rebuild "New" New spindle, new bearings, stainless parking brakes, and new rubber bushings. My half shafts have new u-joints and I am using the Hevi-duty adjustable strut rods with poly bushings, K-bee gas shocks and fiberglass spring (no sway bar)

My question is, my car still feels twitchy (back end loose) in sharp corners (or agressive lane changes for that matter). Do I need to replace the trailing arm bushings with Poly bushings or add a sway bar or both? I am running stock ralley wheels with 50 series BFG's. I am also running a 1.125" front swaybar on stock front suspension (also completly new)
 

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Replacing the yokes may not do much. You really have to remove them to measure them and that will tell.I suspect the rebuilder didn't know much about setting these up beyond a stock setup. If the diff is otherwise ok then you may as well leave it alone.
The rear sway may be from the yoke endplay but I would look at the alignment again and may sure nothing is loose.
 
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