krf

I found lots of info on this subject matter on here, but not sure I have the correct "picture".

I recently purchased a 67 Coupe that has had a new rear end installed recently (last 6 months or so). Half shafts, u-joints, differential case all looks like new....you could eat off of it!

Anyway, thought I would like to set a "baseline" for the car, so I took it in for an alignment at a shop that has some experience with corvettes. While there , the alignment tech called me back to show me something that concerned him.

With the car on the rack with the wheels hanging, both the left and right rear tires would flex noticeably top to bottom and side to side. I had him move the tires while I looked underneath. When he moved the tire, the only thing moving underneath was the half shaft yoke moving in/out of the differential case approximately .25 to .50 inch. Everything that I can see bushing wise underneath the rear looks new...the car had a suspension rebuild back in 2001 or so, and has 5000 miles since then.

The alignment tech checked the front end alignment and rear alignment with the car now sitting on the alignment rack and both front and rear were spot on with minor tweaking!

I did see a small amount of differential fluid residue on the floor of my garage about the size of a quarter directly under the diff.

I just drove this car over 600 miles with zero issues (no noise, just smiles).

My concern is whether I have a bearing or trailing arm problem that I am not seeing. I have no noise and the car tracks perfectly. Other than figuring out where the diff fluid is coming from I have no complaints. My understanding from the post that I have read on here is that the side shaft yokes moving in/out is normal....should I be concerned?

Thanks!
Keith

larrywalk

The C2 and C3 side yokes are almost always forced inwards by the force reactions of the suspension geometry. Each side yoke end bears on the spider gear axle between the yoke ends. As wear continues over the years, the ends of the side yokes wear and allow the yokes to gradually move inwards.

At the inward end of the yoke, there is a thin circlip which keeps the yokes from falling out during installation, but if the wear on the end of a yoke exceeds about 1/8 to 3/16", it reaches the near end of the circlip's groove and will cause the circlip to fall off into the differential case.

Generally, a rebuild of a diff will reduce the end play of the side yokes to less than .030", but if you have more than ~ .080, it's probably time for a rebuild and side yoke replacement.

Look for forum posts by GTR1999; he does a great job of explaining the rebuild operation and has lots of good pictures of the diff innards.

Revette

Did GM ever have a problem with the yoke ends lacking hardness? I had a '79 that had a real "clunking" as I would turn a corner and many of the old-school guys told me to add whale-oil (or whatever the GM additive was) to the rearend for the posi clutches. My '79 was very low mileage (a year or two old) when we pulled the rear end, we found the ends of the yokes had mushroomed over and trapped the clips in the destroyed ends of the yokes. The rearend was total junk. When we pulled it apart, if you put the car on a hoist, while grabbing a wheel with one hand at the top and the other at the bottom of the tire, if you rocked the wheel, I swear you could slide the yoke in and out of the housing about 5/8 of an inch. When the car sat on the ground, the rear wheels had a definite tip with the tops of the wheels in toward the center of the car.

Ironically, my '66 still has a totally original profile when viewed from the rear of the car. I checked alignment two of three years ago and it was "spot on".

larrywalk

I also should add that over the years this kind of yoke wear will cause the required toe-in of the rear tires to eventually become toe-out. If you've ever tried to corner hard with zero, or worse, toe-out, on the rear tires, it will be VERY loose!

nassau66427

Another possibility is that your side yokes could have been assembled without the clips. The absence of clips would allow the movement you describe.

Some guys swear by not using them.

MiguelsC2

Sounds like they did everything but redo the bearings. They can be real tricky. Maybe they were just done wrong?

Ps. The diff. fluid is probably coming from the filler plug. I added an o-ring to mine.

krf

Thanks for the "heads-up" on the Oring! Might as well replace the wheel bearings just to be sure....everything else looks new.

Thanks again!

Keith

krf

Thanks for all the excellent replies. Sounds like I will just pull the side yokes and find out for sure, then do the wheel bearings for "peace of mind". Gotta love this forum!

midyearvette

...........they should be used though( clips)

66since71

Before you open up the differential, actually measure the side yoke end play ( a cheap Harbor Freight dial indicator will work). I would have bet mine were moving 1/4 inch, they measured 0.040"... i.e. Just fine.

Some movement at the tire is normal... Is your alignment tech current on older Corvettes?

Harry

Mike Ward

Do you mean 1/4" to 1/2" or 25 to 50 thousands of an inch? If the latter, that's normal.

magicv8

I swear by not using them. You can disconnect 4 bolts at the spindle flange and slide the axle assembly and yoke out to see if the yoke is worn.

... and IMO if your yokes wear to the point of the clips popping off, the slinger (looks like a large washer) welded to the yokes will contact the diff casting.

MiguelsC2

Make sure the wheel bearings are setup by someone very experienced in doing the Vette bearing work.

May I suggest Bairs? They are highly reccommended here on the Forum. They did mine to perfection. Worth sending out.

http://www.bairs.com/bearing.asp

midyearvette

hmmm...never thought of it that way....

krf

Harry...

You are correct....I should have taken a scientific measurement and not just "eyeballed" it. I have a dial indicator for just such occasions, unfortunately it was in my tool drawer at home at the time.

I will get the car on the lift and take some better measurements. As to the tech, knowledgeable in alignment, but probably not on older corvettes....I have to give him an A for effort however.... he called a gentleman who did, then came out as I was about to leave and asked to put the car back on the machine while he and I both got a lesson via phone link in alignment of C2's! Turns out the gentleman on the phone was busy at the time, but liked the old cars and wanted to pass it along.

I'll get some measurements, but I can't be certain on the wheel bearings as the car is new to me, so I will take 1sttexan's advice and get them done, but I will measure the side yoke deflection before sending the trailing arm assembly in and measure it again when it returns from rebuild and compare the difference.

Note: I just went through the receipts on the car from the prior owner....the car got a rebuilt differential and both side yokes replaced by a chevy garage (Eckler parts) less than 300 miles ago to the tune of ove$2400 bucks....ouch! I don't think my problem is with the differential or side yokes now that I found that....time to concetrate on the wheel bearing, rear suspension rebuild???

Thanks again for the reply!

Keith

krf

1sttexan,

Just spoke with Ed at Bairs....nice people....I'm sending my entire lower trailing arms to them for rebuild....I just found the receipt from the prior owner where the car got a new differential and both side yokes to the tune of $2400+ bucks just 300 miles ago! ouch!(read Chevy garage) Unless somebody goofed up the diff/yokes....the play I'm getting must be in the wheel bearing/lower trailing arm. Since I don't know what was done with them, the prudent thing to do seems to be to send them to Bairs and get them squared away once and for all!

Many thanks for the tip!

Keith

krf

Hello Mike,

Unfortunately it's more like .25 to .50 inches, but now that I have it in my garage...time to put it on the lift and make sure of the measurement.

Note: I just went through the receipts on the car from the prior owner....the car got a rebuilt differential and both side yokes replaced by a chevy garage (Eckler parts) less than 300 miles ago to the tune of over $2400 bucks....ouch! I don't think my problem is with the differential or side yokes now that I found that....time to concetrate on the wheel bearing, rear suspension rebuild???

I'll get the car on the lift next week, measure the side yoke endplay before taking the trailing arms off, send them off for rebuild, reinstall and check it again. If the side yokes come out while I have the half shafts off, I'll know there is no clip installed on them (even if that is no big deal, I'll have to at least open the rear end and look for them, just in case they are in there )

Many thanks for the reply!

Keith

krf

MagicV8,

Many thanks for the info....now that I have spent some time researching this, you are not alone in your assessment of what the clips do. One tech article I read stated that they are there to simply hold the side yoke in so that it does slip out during assembly....not sure on that one, but sounds logical!

Thanks again!

Keith

nassau66427

If that's the case I wonder why Chevy recommends that for severe use (racing), the side yoke end play be reduced to less than .005"? (Chevy Power Service Manual)

shemp

Keith, You won't be dissapointed w/ Bair's they did an awsome job on mine. Shemp
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