C2 side yoke end play

[John M.]

Can someone tell the spec. for the maximum end play for the side yokes on a midyear differential?

Regards, John McGraw

[Joe L.]

Re: C2 side yoke end play

John------

No GM spec was ever published. My own "spec" is that at about 1/16" end play, one should begin to be concerned. At about 1/8" end play, the unit needs to be torn down for inspection and, likely, replacement of the stub axles.

[John M.]

Re: C2 side yoke end play

Thanks Joe,

The worst side was less than 0.050, and the other side was about 0.025. I thought that I remembered something about 0.020 being max, and was concerned. The stub axle ends look very good, and the cross pin shows almost no wear at all.

Regards, John McGraw

[Joe L.]

Re: C2 side yoke end play

John-----

At those end-plays there's absolutely NO reason for concern, at all. Plus, I did not realize that you had the unit already torn down. The "final word" is the condition of the stub axle ends. If they're, apparently, unworn, all is well. The center pin rarely shows any wear. That's because it's heat treated to a much higher Rockwell hardness than the stub axle ends.

One thing to keep in mind, though: the stub axles are case hardened. So, the thickness of the hardened material is not very great. This causes wear to occur in a "non-linear" time frame. Consequently, it takes a long time to wear through the case hardening (not so long for some PRODUCTION and SERVICE examples from the later 70's that were poorly heat treated), but wear proceeds at a MUCH faster rate after the case hardening is worn through.

However, if the ends look good now and with the kind of mileage that the vast majority of these cars see now, they're, essentially, "lifetime" axles.

[Gary R.]

Re: C2 side yoke end play

As Joe said there was never a spec on this, at least I never found one. Case hardening usually is about .030 deep and again as Joe said the late C3 are very prone to failure from poor quality work of the period.
I recommend replacing them if there is more then.040-.050" on them IF you have the diff apart. If it was in a car and otherwise ok I would recommend checking them from time to time.
If you use the rebuild yokes and they are fine a lot of the endplay will be determined by how the posi is setup. As many know I set them up without the springs for several reasons. Once I'm through with a rebuild the last thing I install are the new yokes. Most times I have to face grind them to set them to the .005-.010" endplay I like. I used to set them to .002 but have since opened them up a little.
I just rebuild a 70 LT1 diff with 90k miles on it. The yokes had only .010 wear and were reused. If you have the yokes out install the snap ring and measure down from the end of the yoke to the ring. New they are .187 +/- a couple of thousands. You may find your still ok and tighter then you thought, the rest of the play may have been in the posi shims.

Gary

[John M.]

Re: C2 side yoke end play

Thanks Gary,

Just the kind of info I was looking for. I measured both stub axles today, and they both measured a tad over 0.190. From these measurments, it is clear that the side play is due to rearend setup and not wear on the axles. The rear showed no evidence of having ever been opened up in 40 years, so we will be pulling the posi unit apart to rebuild, but except for this and a new set of seals throughout, the rear will go back together as it came apart. The wear pattern on the teeth is beautiful, and the races on all the Timkens looked perfect. I marked the nut and pinion so I do not even have to replace the crush sleeve. I will tighten it to it's original location, and then add a little to it!

Regards, John McGraw