krf

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

Shemp....

They say "a picture is worth a thousand words", well you "nailed" it!

I'm sold!

Many thanks!

Keith

Powershift

Brian and Ed at Bair's did my trailing arms last year. Quality work and good people. You made a good choice.

Larry

MiguelsC2

I suggest clear coating all that pretty clean metal. It will keep things looking new longer and prevent ugly surface rust. It will also extend the life of the Cadmium on the brake shields.

Revette

I see my initial question has not been answered by anyone in this thread. I asked about the hardness of the splined yoke ends because my '79 (same rearend configuration as my '66) had massive problems in '81 with only 12,000 miles on the car. I asked because my ex-wife ended up replacing the rearend with someone's aftermarket unit when the original GM unit failed and since this was prior to the internet, was there GM service bulletin?

krf

Revette,

I'm sure I'm not qualified to answer this, but from what I have read the original yokes were only hardened for a limited amount on the business end if any at all. In time, the limited hardened area would wear away, giving way to the softer metal which was much quicker to fail/wear thus resulting in more and more yoke play.

I have spoken with a shop who specializes in differentials for corvettes and they commented that they used Yokes that were hardened on the ends, but cautioned that some were not.

Also, others have commented on this forum about adding hardened steel to the end of the yoke (welding), then machining it to "tighten" the tolerances, thus limiting the amount the side yoke can actually slip.

I too had a 1979 when I was in the military, and my differential went out on me while TDY at Luke AFB to the tune of $1200 bucks! (a lot for a 2nd lewie)

I would think the lesson here is to make sure if you replace your side yokes that you do so with ones that have the ends hardened. If you find yours have worn, there are those who have welded on a hardened area, machined it to whatever specs they desired, and put the differential back in service.

Not sure if that answers your question or not....I have no idea on the existance of a service bulletin....maybe someone else knows???

Keith

Mike Ward

Yes, the late 70s yokes were of poor quality due to insufficient depth of case hardening. The additive your buddies made you add made no difference. I've never seen a service bulletin on this and would be surprised if there was one.

65tripleblack

I believe that 1/4" to 1/2" of end play is impossible! If you have 1/8" end play, then you have a fairly severe problem. As someone said before, you are looking for less than 0.010" end play, ideally.

Excess end play can be due to the inner stubs of the yokes being worn, as was mentioned before (once the .005" case hardening wears away, erosion is fairly rapid). The center of the spider shaft, where the yoke stubs abut and rub, tends to wear flat. Another cause of play is excessive wear in the clutch pack. If you raise one rear wheel, and rig up a torque wrench to the hub, then the break-away torque should be 60 foot-pounds. Check this number, but fairly sure that it is around 60. Last time I rebuilt my posi unit, I measures the breakaway torque at 80 ft-lbs.

magicv8

IMO because gymkana/road racing hi lateral Gs with wide tires on uneven tracks that allow cars to unload (or even become airborne) would hammer the diff between the yokes.

All I do is drive my car hard in the streets on radial tires that fit in the wheel wells - from coast to coast and border to border - occasionally at triple digit speeds - sometimes power shifting through the gears for fun. No clips are no problems for me in the 24 years I have owned my roadster and it has been without them.

As a side effect, having no clips makes installing new Ujoints or diff seals really easy.

63Corvette

Brand new, there was significant lateral movement of the stub axles in the differential housing.
Note: for drag racing, the circlips could be left off entirely. Therefore the differential could be changed out in half the time if there was breakage during drag racing launches.

66since71

Because the half shaft is also the upper control arm. The loaded side's shaft is in tension when cornering, so the clips do matter. If youre replacing the strut rods with rod ends for racing, then the half shaft ought to be just as tight.

Obviously it works without clips, but it's not what the engineers intended.

Harry

DansYellow66

My differential lacked clips when I bought my car. When I rebuilt it I installed new yokes from Bairs and clips - because that was what the GM assembly manual said. One new yoke had almost no play while the other had noticeably more - never measured but probably not much more than 1/8 inch. That may just be the way they are as someone indicated above, or may be some wear in my rear end. But - I'm suspicious if those C-clips were really intended by design to take any regular and significant loading to limit outward movement of the yoke, even in aggressive driving with stock tires. I think that stock - outward movement and loading must be a rare situation because I don't see those clips and the yoke grooves being capable of taking a 100,000 miles of regular cyclic loading. My 2 cents

Pilot Dan

Keith, with the side drive shafts removed, see what the side to side play is like in the differential itself. I had over 1/4 inch play in mine and was convinced my side axels were worn to a nub. When I pulled the differential, I discovered the center pin was moving side to side in the case which was allowing both axels to move in and out at every turn multiplying the play. The cure was to install an oversized center pin in my case and not to replace the axel shafts. You won't know for sure until you drop the rear and take a look. GTR1999 (a/k/a Gary Ramadei) did a super job on the rebuild. Check the threads for a wealth of info he has posted on these rears. Pilot Dan

krf

[QUOTE=Pilot Dan;1576584470]Keith, with the side drive shafts removed, see what the side to side play is like in the differential itself. I had over 1/4 inch play in mine and was convinced my side axels were worn to a nub. When I pulled the differential, I discovered the center pin was moving side to side in the case which was allowing both axels to move in and out at every turn multiplying the play. The cure was to install an oversized center pin in my case and not to replace the axel shafts. You won't know for sure until you drop the rear and take a look. GTR1999 (a/k/a Gary Ramadei) did a super job on the rebuild. Check the threads for a wealth of info he has posted on these rears. Pilot Dan

Thanks Dan....

I plan to get her on the lift next week to pull my trailing arms....good time to open the differntial and see what's going on in there.

Many thanks!

Keith

riacreedon@gmail.com

Interesting stuff here.
I'm rebuilding my '70 rear. Thinking of buying trailing arm ***'ys from Duntov Motors. Any opinions about their materials and workmanship? Also, regarding the side yokes: anyone heard of the clips coming adrift, getting into the ring & pinion - and destroying the diff.?

Mike Ward

This topic gets thrashed here occasionally but more frequently on the C3 board. There's a small but vocal minority, most of whom I believe are sporting a cranial Faraday cage, believe that large amounts of yoke end play constitute a road safety hazard.

TheSaint

I was told to change the bolt(looking like the one to the left on the picture)everytime i change oil on the differential
Where in the differential is that bolt supposed to sit?

Also if the strut rod bushings are worn i suppose you will get play?

It cant be that hard to change the side yokes, bearings, seal and snap rings? I suppose the most difficult thing is to pull the old bearings?

Note that if i have to do this i have never done it before but i have a friend that have been working with Corvettes his hole adult life

Mike Ward

That bolt attaches the trailing arm bushing to the frame. Nothing to do with the differential.

TheSaint

Mike it is not the bolt on the picture but it is small and looks like the one to the left on the picture

Mike Ward

There's no bolt near the differential that looks like that, nor do I know of any bolt that needs/should be changed with fluid change (?)

nassau66427

I think you're talking about the pinion shaft lock bolt.

The pinion shaft may get screwed up as the yokes wear.

It's a good idea to replace it if you replace the pinion shaft.

Don't overtorque it.