CrossedUp

I had a chance to borrow a lift last night for about a half hour. I wanted to do a general visual inspection and get the stamp number off the tranny (which matches BTW).

I grabbed one of the rear tires at 6 and 12 o'clock and rocked it in and out and there was a significant amount of play, felt like ~1/2" or so at the tire's outer edged. I checked the other side and got a similar result. The good news (I guess) is that the play wasn't in the spindle bearings but in the suspension. I could see the trailing arm rotating slightly back and forth. My time on the lift was limited so I wasn't able to do a thorough investigation. The BIG question for me is, is this a safety concern? It seems to drive okay but, having never driven a C2 with fresh rear suspension, I have nothing to compare it with.

It has a fiberglass spring if that's of any relevance.

Thanks,
-Doug

Easy Rhino

Without knowing the cause of the flexing, it's hard to say; however, not knowing the cause of the flexing -an unknown problem - excludes driving this car at least until the cause is understood.

Not worth risking your life, and others, as well as the car. I would recommend parking it.

Add to that, I see you are in Brentwood, and have stated a safety concern publicly. As a result, if someone gets hurt, you're gambling with a potentially huge legal judgement.

jerry gollnick

Fiberglass has no impact on this.
If you are talking horizontal displacement and NOT rotational then the movement comes from worn out or improperly adjusted bearings(not likely) or "C" clips missing or broken on axel stubs. In either case its time to have someone familiar with old Corvette suspension take a serious look at whats going on.

CrossedUp

Jerry, The movement is in the direction that would cause a change in camber. There was no perceivable play in the spindle bearings, just in the suspension. I did not check for spindle end play though.

Mr D.

What does your strut rod bushings look like?

CrossedUp

Here you go D. Bushings look old and ugly but don't move much when "nudged" with a pry-bar. I don't understand the corrosion on the left rear corner, the undercarriage looks pretty clean everywhere else. Going to have the suspension looked at today.

Order:
L. Inboard
L. Outboard
R. Inboard
R. Outboard

65GGvert

If you watch where the axle stubs go into the rear axle housing, you'll probably see them sliding in and out. My opinion is that if you do, you need to replace both side axle stubs. The ends wear and become shorter, allowing movement. If you have play there, the rear will feel like it's sliding or shifting and just loose. I had one on a 78 wear so much that the bolt on the u-joint was hitting the housing on a hard turn and causing a loud clunk.
Whatever it is, you need to fix it, you don't want the rear tires flopping in and out 1/2" depending on direction of the car turning. Verifying the axle play is easy, just watch when you push in and out at 12 and 6 as you did, it's obvious if the movement is caused by the end of shaft going in and out of the rear housing.

DansYellow66

If the 1/2 inch of movement is at the top of the tire that amounts to about 1/4 inch in/out movement at the side yoke in the differential. That is not unexpected - a lot of Corvettes do not have C-clips installed on the yokes. The yokes are kept seated by the normal load of the camber and restraint below the centerline of the wheel by the lower strut arms. If your trailing arm and strut rod bushings are all in good shape and tight, and if you can correctly align the camber and toe-in at the rear, your don't have anything to worry about. If you have excess negative camber in the rear that can't be adjusted out, then there is probably a good chance the ends of the side yokes are excessively worn and need replacing.

And lastly - while my car didn't have c-clips installed when I purchased it, when I restored it and replaced the side yokes, I did install c-clips. I know they are not absolutely necessary but if you are in there anyway, why not. As long as they are securely seated and the yokes are not excessively worn they can't harm anything.

CrossedUp

That's it GG! The guy at the shop (Corvette Connection in San Jose) said that up to 1/4" of yoke end play is acceptable which seems excessive to me. Mine are no more 1/8". If it makes any difference, it's non-posi.

65GGvert

I'm going to have to disagree with Dan on this one. Read this thread and keep in mind that even if yours is 1/4", that's .250, several times the maximum allowable. If you google corvette axle end play, you'll find some more threads with pictures and even a video of a car with worn stubs. If you have that kind of play and turn a corner, the opposite side will move out, and then when you turn vice versa. That's a lot of banging against the internals of the rear axle, and I promise you'll feel the slop in your rear during turns.
I have explained my opinion on this, and I'm not going to get pulled into a back and forth argument over this, just take a look at this and then research some other threads. Good luck with your fix, be sure to post back what you find.

https://www.corvetteforum.com/forums...-end-play.html

CrossedUp

Thanks Dan. In my first post the 1/2" of camber displacement was a WAG because I had no measuring tools when the car was up on the lift. It's actually about half that as measure from the top of the tire.

There's quite a range of differing opinions on what's tolerable. In this thread: https://www.corvetteforum.com/forums...estion-c2.html one opinion is to not let them go past .050" and yet the local "Corvette Expert" said up to a 1/4" is acceptable.

65GGvert

That's different. If yours are no more than 1/8" and you don't feel any bad effects, I wouldn't do anything. It doesn't wear quickly unless you're constantly racing or autocrossing. But if, as you said, the tire moves 1/2" in and out, that's bad for the tires, the rear, and the driving feel. I tried and I can barely feel any movement when I do as you did.

65GGvert

You can always address it if you need to get into the rear for something else, like changing ratio, adding posi, etc.

DansYellow66

I haven't found in the GM service manual where a tolerance for yoke play is stated - maybe it's buried somewhere else in a Technical Bulletin or something. But if GM did ever publish a tolerance, it would only be relevant if C-clips are installed, and many, many Corvettes have been running around for decades without C-clips and without any issues due solely to this. Or at least as long as you aren't planning any Dukes of Hazard's jumps.

So yes, if GM ever published a tolerance I'm sure it was less than 1/4 inch and probably even less than 1/8 inch with C-clips installed.

Incidentally - I believe I remember from prior posts that the only issue about measured play at the yokes (with c-clips installed) was that it could provide some indication of wear of the .040 - .050 inch of hardening on the ends of the yokes. But it's not a sure means of determination. When I installed new yokes and clips in my car I didn't measure the exact play but I recall that one side had relatively little play and the other side had twice as much. That could have something to do with some wear inside the differential on the big pin they ride against. But the best way to determine if the yokes are worn through the hardened ends is to remove them and measure them.