C2 differential ID

[Michael G.]

Re: C2 differential ID

We certainly want to include all the various and sundry MIke's who populate the forum, the more the merrier.

In any case, as long as we have such an illustrious crew of Mikes and other equally special folks here, and we're talking differentials, a couple of real technical rear axle things are of particular concern to me:

1. With my 65 on the lift, if I turn the rear tire, at one point in the rotation there is, what I would describe as a "hitch". Is this a u-joint issue?

2. My diff now has two bottles of posi additive fluid in it and after the oil was warmed for 20 miles or so, it has a huge clunk after I stop and turn left. Is there a limit as to how much posi additive I can add, or is there perhaps something wrong with the posi?

Thanks,

[Joe L.]

Re: C2 differential ID

We certainly want to include all the various and sundry MIke's who populate the forum, the more the merrier.

In any case, as long as we have such an illustrious crew of Mikes and other equally special folks here, and we're talking differentials, a couple of real technical rear axle things are of particular concern to me:

1. With my 65 on the lift, if I turn the rear tire, at one point in the rotation there is, what I would describe as a "hitch". Is this a u-joint issue?

2. My diff now has two bottles of posi additive fluid in it and after the oil was warmed for 20 miles or so, it has a huge clunk after I stop and turn left. Is there a limit as to how much posi additive I can add, or is there perhaps something wrong with the posi?

Thanks,

Mike-------


1) If the suspension is "hanging" when you rotate the tire, that is likely the source of the "hitch" you describe. However, if the suspension is at or near normal, on-road configuration, then what you describe is very likely a half shaft u-joint problem.

2) I don't think there is any sort of limit as far as posi additive use goes. However, I've never known a differential to require more than 2 bottles to eliminate "chatter".

[Mike T.]

Re: C2 differential ID

Mike - What kinda lift? Is it a 2-post where the Trailing Arms hang down? if so, could it just be the u-joint at an extreme angle?
On your second question, are you saying it doesn't happen when going straight or right after a stop?

[Michael G.]

Re: C2 differential ID

1. Suspension hanging down.
2. I've only seen it on L.H. turns after a stop sign, after the fluid is hot. Its so severe that I stop driving when it happens, so I don't have a lot of data points...

[Michael G.]

Re: C2 differential ID

Thinking about draining all the fluid and starting over with all new. The posi additive I used is not Delco, so I ordered some Delco and it'll be here tomorrow.

[Duke W.]

Re: C2 differential ID

1. With my 65 on the lift, if I turn the rear tire, at one point in the rotation there is, what I would describe as a "hitch". Is this a u-joint issue?


,

...could be a u-joint grounding problem. If you apply a bit more torque when it stops rotating notice if the wheel rises a bit, starts to rotate and then drops down again. This is U-joint grounding. It's most common on '63s with the early cast iron axle drive flanges.

Rebound is controlled by shock extension, and some may extend too far.

All OEMs that offer clutch type LSDs use the same anti-chatter additive. Napa sell it, p/n NCB 4285V.

Duke

[Michael G.]

[Joe L.]

Re: C2 differential ID

Hi Duke, thanks. There doesn’t seem to be any contact with either flange when the axles rotate to the position where it takes more effort to turn. I couldn’t see any significant lift of the wheel in that position either. It only happens at one rotation position, not the two I would expect if the flanges were contacting. I think it might be a good idea to take the axles off and inspect the u-joints.

Mike------


How old are the u-joints?

[Michael G.]

[Michael G.]

Re: C2 differential ID

Well, I got around to doing one side today and both u-joints and the bearing seem fine. More tomorrow.

[Michael G.]

[Mark M.]

Re: C2 differential ID

Mike, there is a chance the posi case inside cracked at the cross pin. I set up a lot of these rear ends. I had a friends 66 BB car here a few years ago doing similar symptoms. His cracked from the pin to the large window area on one side. The other side was still holding and in turns the stress on the case is the greatest. Back in the 80's I took a hard turn in a 65 and the case split locking up the rear end leaving me in need of a flatbed. When I set up a posi case I polish the window area and do a dye test for cracks. Often the cases have cracks you can see before doing any thing to them but didn't break. The late 69-79 cases are the strongest as are new eaton units. A scope camera in the filler plug may be able to see an obvious crack. Unfortunately the only other way to check is pull the rear end.

[Michael G.]

Re: C2 differential ID

Thanks Mark. I've been wondering all along if there was something wrong with the posi. The noise involved is not just a clunk, its loud and metallic, enough to make me thing something is significantly wrong. Now that I know that the other possible causes of the noise are ruled out, we'll give this fluid change a chance, before taking out the differential. I'll probably throw in the 3.36 in the pics above, while I get the 4.11 looked at.

[Mark M.]

Re: C2 differential ID

The noise may be the ring gear digging into the inside of the cover. Seen a number of these on rear ends with partially cracked /split posi case. Good luck

[Edward J.]