8.75 cone sure grip locked on turns

[plumkrazee70]

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.

 

[dadsbee]

Go do figure eights in a parking lot for a bit.

 

[plumkrazee70]

Go do figure eights in a parking lot for a bit.

I read that, what does that do?

 

[dadsbee]

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.

 

[plumkrazee70]

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.

Huh. Worth a shot. I'll have to try and find a big empty parking lot.

 

[dadsbee]

Start big and work tighter and tighter till you're going full steering wheel lock.

 

[mopowers]

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.

 

[plumkrazee70]

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.

 

[dadsbee]

FURD is the best or Spicer which is the same. Give what you have a few loops and see if it cleans up.

 

[RustyRatRod]

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.

 

[Bewy]

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...

 

[plumkrazee70]

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?

 

[RustyRatRod]

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.

 

[Bewy]

Plum,
Yes synthetic. No additives reqd. I believe all Redline oils, greases etc are synthetic.

 

[plumkrazee70]

Plum,
Yes synthetic. No additives reqd. I believe all Redline oils, greases etc are synthetic.

Thanks. What weight?

 

[Bewy]

I use the 80w140

 

[str12-340]

Be sure your rear seals (all of them), and gasket seals are up to it, synthetic leaks from Much tighter spaces...

 

[plumkrazee70]

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.