8.75 cone sure grip locked on turns

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plumkrazee70

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I have a cone type sure grip in a 489 case with 4.10 gears. I had @RustyRatRod rebuild/resurface the cones and had a local shop set up the new 4.10 gears. All the parts (gears, seals, bearings, etc) I got from Dr. Diff. Also used a crush sleeve eliminator.

I put 80-90 Sae fluid in it with a bottle of AC Delco friction modifier.

However no matter what the rear end acts like it's locked when making a turn, shaking the whole rear end.

I added a second bottle of modifier, but no change.
 
Works the clutch cone back and forth to get it doing it's thing. Works great with clutch units, nothing to lose trying it with a cone.
 
Start big and work tighter and tighter till you're going full steering wheel lock.
 
My cone unit did the same thing after I rebuilt it. Figure 8's worked perfectly. Just have to get the oil and friction modifier worked into it.
 
Ok. Well that makes me feel better. Is the Delco friction mm modifier ok? I've read that the ford modifier may be better. But I work for a GM dealer.and.we had it on the shelf.
 
FURD is the best or Spicer which is the same. Give what you have a few loops and see if it cleans up.
 
I have a cone type sure grip in a 489 case with 4.10 gears. I had @RustyRatRod rebuild/resurface the cones and had a local shop set up the new 4.10 gears. All the parts (gears, seals, bearings, etc) I got from Dr. Diff. Also used a crush sleeve eliminator.

I put 80-90 Sae fluid in it with a bottle of AC Delco friction modifier.

However no matter what the rear end acts like it's locked when making a turn, shaking the whole rear end.

I added a second bottle of modifier, but no change.
Give it time. It'll break loose. Try doing some figure 8s slowly in a parking lot.
 
Might also try a different oil, one that comes ready for use with limited slip diffs. My car, also, has the cone type LSD, had a slight whine on coasting. Redline oil cured the whine. I know the whine was caused by gear noise, not the cones, just pointing out how different oils can make a difference...
 
Might also try a different oil, one that comes ready for use with limited slip diffs. My car, also, has the cone type LSD, had a slight whine on coasting. Redline oil cured the whine. I know the whine was caused by gear noise, not the cones, just pointing out how different oils can make a difference...

Is that a synthetic? Is it ok to use a synthetic in these old rear ends?
 
Is that a synthetic? Is it ok to use a synthetic in these old rear ends?
Yes. It won't hurt a thing. I would read up though, as you may still need some sort of friction modifier. Being synthetic might mean that it's not necessary, but I am unsure.
 
Plum,
Yes synthetic. No additives reqd. I believe all Redline oils, greases etc are synthetic.
 
Be sure your rear seals (all of them), and gasket seals are up to it, synthetic leaks from Much tighter spaces...
 
Be sure your rear seals (all of them), and gasket seals are up to it, synthetic leaks from Much tighter spaces...

I have green bearings on my axles. I don't believe I have any axle seals. The third member is a gasket. I'll see how the figure 8 works out. Weather has been choppy here lately.
 
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