C2-3 differential backlash

[Michael H.]

Re: C2-3 differential backlash

Gary, when you tune a posi I assume you shim each side gear to where the breakaway spec 50-70 ft.lbs is reached without springs. What happens when the clutch pack wears, there is no tension to take the slack and maintain a preload..

I think the 50-70 ft. lbs spec is WITH the posi springs installed. There should be very little clutch drag without the springs.

Also, from LOTS of experience, I learned in the mid/late 60's that if you set the differential pinion gear rotational backlash at specs, especially the tight end of specs, the positraction will almost always chatter on corners, no matter how many of those little bottles of additive you add.
If I remember correctly, the GM manual called for a rotational clearance of something like .003"? I would shoot for a bit more clearance.

Torque input is what makes the positraction clutches function. The small pinion gears force the side gear into the clutch packs under acceleration. The harder you accelerate, the more force is applied.

The spring pack with plates is also used to load the side gear and clutches so the positraction functions when only a light throttle/load is applied, such as when one wheel is on snow/ice.

[Timothy B.]

Re: C2-3 differential backlash

Thanks Mike,

That's interesting about the differential pinion backlash and the chatter you report. I wonder how close to spec these were set from the factory.

Does the tight backlash make the clutches want to grab at slight difference in wheel speed so it only takes a corner to chatter?

My question is about the crush sleeve being installed just to check the drive pinion tooth contact during set up after the ring gear backlash is set. Is it really necessary to use the crush sleeve when just checking the gear pattern?

[Michael H.]

Re: C2-3 differential backlash

My question is about the crush sleeve being installed just to check the drive pinion tooth contact during set up after the ring gear backlash is set. ?

You should be able to assemble the pinion without the crush sleeve and still make an accurate pattern check,
Since the pinion position/depth is controled by the large rear bearing, and that bearing is pressed completely down to the shoulder on the shaft, it's position is established and won't change.
The crush sleeve is there to keep the front bearing inner race from moving rearward on the shaft.
If you run the pinion nut down just enough to make sure the bearings are making full contact, with a slight drag to remove all end play, that will be sufficient and will work well for pattern check.

[Dick W.]

Re: C2-3 differential backlash

Merry Christmas everyone..



Is the tool that's used for pinion depth still available for the GM ring and pinion gears?

Nominal depth setting tool, available from the aftermarket