Differential Yokes

[matthud]

Is it possible to put new clips on the end of the differential yokes without removing the entire diff from the car. I was replacing my bearings and halfshafts this weekend and found that the one yoke pulled right out. There was no clip at all on it. Is it possible to take the rear cover off and put on a new clip.

 

[GTR1999]

No, you have to remove the differential. The clips are snap rings and the snap ring groove is .187" from the end of the yoke~+/- .010" If you can pull the yoke out either the snap ring fell off- unlikely or the yoke is worn down to the groove- more likely.
Some of the later year C3's had softer yoke shafts then eralier cars or the current aftermarket supply. A lot of guy ask me if it's ok to just replace the yokes and leave the rest alone. I don't do that because if the yoke worn down to the point of the ring falling off where did the metal go to? the oil and into the bearings gears etc. You can if you want to just replace the yokes, but I do a rebuild at this time as it's usually a high mileage and you'll have it out anyway. Of course the factor is cost- $100 for a yoke vs $1,200 for a full blueprinted rebuild with new yokes,gears, bearings,etc.
Check to see if the yoke has already started to hit the housing and "mill" into it.
If you need any help let me know.

Good Luck,
Gary

 

[80convertible]

Gary knows more about corvette diffs then anyone else. He has a great white paper he authored which I read many times. I had the same problem... snap ring was missing. In my case the end of the yoke was not worn (taper was still visible) so I replaced the snap ring. Not sure why the snap ring was gone but I think it was because someone replaced the yoke and either forgot or was to lazy to replace the snap ring. I also found a small hole in the case which I repaired with some JB Weld. I also replaced the seals/gasket and fluid and it's running nicely.

Replacing the snap ring is a good reason to pull the diff, paint it and replace all of the seals and fluid. Here is a before and after of my diff...

 

[matthud]

I am hoping that is what the reason is. The previous owner of my car was incompetent beyond all thinking. I am hoping that he replaced the yoke and didn't put on a clip. But since I have to drop the diff to do any of this I will be able to get a good look. The part that really ticks me off is that I just had the rear bearings done and I put the entire rear drivetrain back together before I discovered this and learned that I can cause major damage driving on that. The part that worries me is that it was like this before, I guess its a good thing I got new rear bearings.

 

[waterboy1976]

Im sure Ill get some flack for saying this becasue technically you can run without the clips holding them in. and truthfully, if a ring falls off into the rear end it really wont do that much damage, BUT coming from experience when I put my new rear end in this year, I was adjusting my strut bars and at the same time watched the side yoke pull out as I was adjusting the alignment...so I pulled the whole thing and put the ring back on. MAKE sure the ring is seated all the way around the yoke, Its easy to install the ring and it looks like it is on but part of it may not be and eventually it will work off.....Crack open another beer and get to yankin........

 

[Vettehead Mikey]

Im sure Ill get some flack for saying this becasue technically you can run without the clips holding them in. and truthfully, if a ring falls off into the rear end it really wont do that much damage,

You shouldn't get ANY flack for this because you are correct- the clips perform no real function at any time the wheels are on the ground.

I did an analysis several years ago and found that there is a MINIMUM of 300 lbs. lateral force 'pushing' the yokes toward the center of the diff, even under the worst turning/sliding conditions.

If someone has a habit of driving with the rear wheels off the ground, or sliding sideways into curbs then the clips would have relevance but probably would also have other issues to deal that are more important.

 

[lone73]

I did an analysis several years ago and found that there is a MINIMUM of 300 lbs. lateral force 'pushing' the yokes toward the center of the diff, even under the worst turning/sliding conditions...

WOW ! That is fascinating. How did you figure that out?
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[waterboy1976]

Thank you Mikey. I am also aware of those facts you present.. I am friends some of the guys at Mallett Motorposrts here in Berea Ohio and they have told me similar things.

 

[Vettehead Mikey]

WOW ! That is fascinating. How did you figure that out?
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Pretty easy- I just gave the basic project data to one of the junior co-op engineering students working in my department at the time and let him sweat it out. Didn't tell him what the application was till he was done with it.

It's actually a fairly simple engineering exercise, to do it you need-

-radius of the tire and wheel (= centre line of the axle)
-vertical distance from the axle centre line to the outer strut rod pivot point
-horizontal distance from the wheel centre line to the outer strut rod pivot point.

With these three dimensions, you can create a map indicating the angle of thrust through the strut rod pivot point. Think of the pivot point as a 'lever' causing the wheel to try to tip inwards. Because it tries to tip inward, the load on the half shaft and side yolk increases, pushing towards the centre line of the diff. If you were to change any/all of the three dimensions above, the load would vary accordingly. I used the stock dimensions as an assumption.

Additionally, if you change the vertical load on the tire and/or if you induce a side load on the tire (simulating going around a corner) the net inwards load on the side yolks vary.

Where we got into the area of having to make assumptions was knowing how much the vertical load on the tire changed as we varied the side load (and vice versa) under actual driving conditions. As a car goes around a corner, weight transfers off the inside tire, but goes onto the outside tire. This increases the force pushing the yolk inwards but at the same time the lateral force on the tire tries to pull the yolk outwards (this applies to the outside tire in a turn). Using the maximums of the total weight of the car in vertical load and 1G in horizontal, the lowest yolk load we could plot was approx. 300 lbs.

We did not take into consideration the suspension extending or rebounding in this exercise, but would think that if you are in a max G turn and just hit full extension of the suspension, you potentially have other more important repair bills coming up compared to a 50 cent snap ring.

 

[GTR1999]

Mike,
It certainly gives good reason for the yokes ends to wear,especially with poor case hardening on some of the later year yokes. Nice info.
Gary

 

[matthud]

How much is a good differential rebuild going to cost me?

 

[waterboy1976]

$500 to $600 for a rebuilt one......with core exchange.......

 

[GTR1999]

I suggest you look into what you're getting for the various price ranges.
Gary

 

[matthud]

Can anyone recommend a place to send mine to be rebuilt if thats the route I choose?

 

[John Kuzman]

I had my '69 rear differential (and trailing arms, strut rods, drive/half shafts)re-built by Bair's. Great service and always available for follow-up advice. They will even send you a shipping box!

www.bairs.com​

 

[Stingray6974]

Matthud,
I can rebuild your differential for you. I have thirty years experience and references. A standard rebuild costs $450.00. It includes:
Timken bearings
Torrington stub axle bearings (the correct ones)
New crush sleeve
Eaton steel clutch pack
National seals
New GM cross shaft
case and housing deburred
caps squared and fitted
spyder gears set at .001-.003 backlash
ring & pinion set at .006-.008 backlash
media blasted and painted
additional parts:
New stub axles $110 each
New gears prices depend on brand and ratio.

Shipping weight is 99 lbs.

Mike