Differential specifications for 81 Corvette

[Kachina]

Hi everyone -

I'm new to this forum and hope to find answers to some questions to prgress a rebuild of an '81 (specifically about the differential specifications).

What is the break-away torque for the limited slip?

What is the correct backlash setting?

Unlike the Eaton type positraction, this model does not have a locating screw thru the pinion shaft. If there some secret to preventing the pinion shaft from slipping out of the housing?

Can anyone help please?

Kachina

 

[69MyWay]

Great questions!

Sorry I did not see this post earlier.


One of our mods here Stingray6974 is an expert on rear ends. Let's see if we can get him to catch this thread.


The best I can tell you is #1, I don't know the break away torque. As far as the front pinion, it is pretty much pressed into place and held there by the crush washers and pinion nut. You won't find a side mount pin to index or hold it into place.

The trick is of course, setting up the rear so that the pinion gear is shimmed for the most appropriate alignment on the rear gear. Otherwise it will not last very long.

 

[Kachina]

Thanks 69MyWay... any help would be useful as it's hard to get hold of really detailed/useful information here in Australia.

 

[Stingray6974]

Hi Kachina,
I too must apologize for not seeing your post earlier.
Backlash: .008" - .009"
The pinion shaft is held in by two small retainers. There should be two small grooves on the shaft about a third of the way up the shaft. The retainers snap in these grooves and ride against the small pinion gears inside the unit.
I'm not sure what you mean by "breakaway torque"?

Mike

 

[Kachina]

Hi Kachina,
I too must apologize for not seeing your post earlier.
Backlash: .008" - .009"
The pinion shaft is held in by two small retainers. There should be two small grooves on the shaft about a third of the way up the shaft. The retainers snap in these grooves and ride against the small pinion gears inside the unit.
I'm not sure what you mean by "breakaway torque"?

Mike

Thanks Mike. Given this is not my car (it's my Dads) and I'm mechanically challenged - I will try to explain...

The diff has been disassembled and there were no retainers for the pinion shaft! The quote "stupid idiot" who worked on it before Dad bought it had "no clue" what they were doing. They now have some retainers.

In some of the reading they have been able to do here, they were reading a recommended backlash setting of .005" to .008" - they were going to work on .006" - but you are suggesting otherwise?

As for the 'breakaway torque' (good question cause I don't know either) but apparently this is the setting on the limited slip unit/positraction and should be somewhere around the 50pound range?

Kachina

 

[Stingray6974]

Hi Kachina,
.005 is too tight for backlash.It will cause a howl and not allow for heat expansion. Too loose is much better than too tight.
I understand now what you mean by breakaway torque. Honestly no one ever uses this type of setting. A new set of clutch discs will have a much higher rating when checking than will a set with 1,000 miles on them. If you like I can post several other adjustments for you.

Mike

 

[Kachina]

Thanks!

Thanks Mike ;worship

I'll relay that information to Dad and let you know.

Thanks to you and 69MyWay for replying. Very much appreciated!

The sooner the Vette is registered and back on the road - the sooner I can plead my case for car-sitting, taking it out for a run etc etc

Kachina