'77 42kmiles

When I pull on rear wheels @ the 12 an 6 position I get movement in the stub axles.... somewhere between an 1/8th and a 1/4 in. I'd say. Normal wear for this mileage?

I believe I'm going to clean up/paint everything back there...I have some Bilsteins to install and thought maybe do the 'glass spring also so please tell me if I need to address the stub movement.
Thank you.

 

Although there is no official spec for max acceptable wear, 1/8" is way too much and indicates severe wear.

Take it apart and measure from the inner end to the snap ring groove. New is 0.187". The ends are only surface hardened. Once it wears through the hardening it chews through it pretty quick. Personally I would replace once the end-to-groove distance has decreased by 0.030" or so as that is well past the hardening.

 

Measurement I was given by Gary (gtr1999) for the distance from the snap ring to the face is that it should be between 0.180" and 0.200".

 

Thanks guys.

Yeah, I've got a problem here....just went and looked at it up on the lift and I can see the stub u-bolts are starting to hit the diff. housing. Yikes!

Is this common @ 42k miles...or do I need to be looking for something else that is wrong?

 

Common for late 70's cars. Earlier (60's) had much better hardening and lasted longer. I'm using a used set from a mid 60's car and you can still see the machining marks on the end and they measured 0.187", same as new.

 

I replaced my 3.55 with a 4.11 earlier this year. It had about 100K miles on it and never opened to the best of my knowledge having bought the car with 43K mile on her. I can confirm the 0.187" noted by Zwede as mine measured that. My stubs had worn down about 0.120". I had measured wear over the past few years hence my decision to replace the rear end this year.

 

excessive side yoke end play can come from two places worn side yokes and/or worn posi plates.

 

I have worked on plenty of original 63-72's that had over 100k miles and the axles were still good. The best of the bunch, from 63- 67 were .190-.200" measured from the axle face to the snap ring. There was some variance with the snap ring thickness of 001-003" as well. I think that was just from different suppliers of the period.

The rebuilt axles are all over the place, where they were once consistently in the 180-185 range I see them now in the 170-172 range which is terrible. Then the last group I got in I found one at 200, another couple at 180-182, and the last one was under 180 if I recall. Splines were not machined correctly and would not fit the side yokes, as well as some other things I found. The last new axles I had in was a few years ago and they too were all over the place, many were not hardened. I just checked a new source for HD axles and they were dialed in perfectly. They were hardened correctly, slide right on a side gear, and when checked in the tuned posi I had on the bench had 005 endplay in both sides. I will be checking some others next week.

Axle endplay comes from 3 places

1 - posi setup
2 - axle face wear- not hardened enough common from around 72-79
3- enlongated cross shaft holes in the posi

Most likely it is #1 and #2. Your 77 must have the original soft face axles and if they hit the housing already you should check to see if the seal boss is still there or if the axle crashed into it and faced it off. I have had those in too and some of the housings were wrecked. The cost to machine sleeve them was more then just replacing the housing.

 

If yours look like this one you have issues. I scrapped this out a few years ago, the housing, axles, clutches, posi, were all junk. The only thing worth saving was the pinion yoke and cover. Oil was pouring out the damaged axle seal, the yoke became a fly cutter into the diff ear. The ear means nothing and can actually be cut off as I do with the super 10 and 12 bolts but the damage to the seal bore was too much and again wasn't worth the time to repair.

I would address this now and not drive it until it's fixed. You're never too old to learn how to rebuild a differential at home. Good luck and hope it's still good.