Anyone know if an '82 factory 12 bolt limited slip has anything metric about it?

[72timemachine]

I'm looking to build a '72 5 lug factory 12 bolt limited slip rear end. My friend has an '82 limited slip rear end he will give me out of his diesel c10. Strange thing I encountered last night was when I took an '82 lug nut and tried to thread it onto the '72 lug stud. It did not want to thread on, felt as though it was going to cross-thread, however, when I put the lug nut on backwards, it threaded on fine until it hit the taper or front of the lug nut. The '72 lug nut threaded on the '82 lug stud just fine and with no slop. What's up with that?

I was hoping to use those axles unless I can simply switch the lugs studs from the '72 over the the '82 axles. The '72 rear end was in a dump bed and the person destroyed everything inside by hitting the front pinion yoke which caused the seal to leak. It turned the remaining gear lube into a thick metallic pudding. Clearly I have to remove all the internals, races and all, chemically clean it and start from zero.

Main question is, will I be able to use the limited slip carrier out of the '82 and install it into my '72 housing? If so, I would have to get a different ring and pinion gear, such as a 3.73 because the '82 has a 2.73 set up when I looked at the numbers stamped on the ring gear, 15, 41.

Thanks for any help it is much appreciated.

[MJN]

You may want to check the dates on the ring and pinion of that '82 rear end, they did not come with 12-bolts in those years, so it was swapped in from something older at some point. an '82 would have had a GM 10-bolt axle from the factory. Also, if I read it correctly the lug nut would go on until the taper- I would suspect the lug nut is worn down or crushed on the taper end from years of use. They should both be 7/16-20 threads unless in the past 30 years someone put metric studs in it, hard to say without checking with a thread gage or thread die.
Carriers are different as well- 3.73 and numerically higher use a series 4 carrier where 2.73/3.08 gears used a series 3 carrier.

[72timemachine]

Ok, thank you, my friend brought over one of the '82 axles last night, that's how I got hold of the lug nut...he's not a mechanic and may have thought he had a 12 bolt. Appreciate your help.

Tell me something, Have you ever heard of the 12 bolt pinion gear cracking...as in this is its weakness or is this just something I read which is not accurate. Under normal wear and tear that is.

Thanks.

[gmc684x4]

Pinion gear is pretty tough on the 12 bolt even fairly tough on its lesser truck 8.5 10 bolt
Had a 8.5 10 bolt pinion nut loosen off pinion hit the housing leaving large bite marks after looking around for a

[72timemachine]

Thanks, here is what happened to this rear end. (see photo)

[68Stepbed]

Originally Posted by MJN

You may want to check the dates on the ring and pinion of that '82 rear end, they did not come with 12-bolts in those years, so it was swapped in from something older at some point. an '82 would have had a GM 10-bolt axle from the factory. Also, if I read it correctly the lug nut would go on until the taper- I would suspect the lug nut is worn down or crushed on the taper end from years of use. They should both be 7/16-20 threads unless in the past 30 years someone put metric studs in it, hard to say without checking with a thread gage or thread die.
Carriers are different as well- 3.73 and numerically higher use a series 4 carrier where 2.73/3.08 gears used a series 3 carrier.

Actually, the 81-82s had 12 bolts if they had the diesel engine. My son's 81 had the 12 bolt and it was originally equipped with the diesel.

[72timemachine]

Thanks 68stepbed, I'm going to go over to my friend's house and dive under that truck and check it out, there could be hope yet.

[gmc684x4]

Check the Pinion teeth are any damaged ?
my Brother had his lesser 8.5 bolt do that we looked high and low for another diff with 3.73 gears gave up checked the pinion no damage bearings felt good
pinion nut backed off installed a new nut with locktite 3 years latter it still runs and drives with no issues

[gmc684x4]

This pic is a gov Loc diff lots of ppl avoid them
A posi will have a spring and clutch pack

Also take your diff cover with you or use the two pics you can see in my pic the ten bolt is a more round case then the 12 bolt

[72timemachine]

You got lucky I suppose. I'm not kidding when I said "metallic pudding", so I cannot imagine anything inside escaped surface damage from all that metallic grinding away....eh gad but thanks for the tip.

[72timemachine]

I have to leave right now but doesn't the gov lock work by way of centrifugal force?

What causes the limited slip to engage? Does that too use centrifugal force?

Thanks for the information.

[Greg58]

I used to have an 82 Sub 1500 4x4 and it had a 3.42 12 bolt.

[68Stepbed]

Originally Posted by 72timemachine

I have to leave right now but doesn't the gov lock work by way of centrifugal force?

What causes the limited slip to engage? Does that too use centrifugal force?

Thanks for the information.

Gov-bomb- Centrifugal force and friction clutches. However, they tend to only work in a straight line or left turns. The reason behind the nickname "Gov-bomb" is sometimes, the centrifugal weights don't engage the clutches and only wheel spins then the weights suddenly lock both axles together and if wheel speed is fast enough....BOOM!!!!

A true limited slip(posi) uses clutch packs with pre-load springs and plates. The springs give enough under side load to allow the inside wheel to turn slower, while still maintaining grip.

[Bigdav160]

This is how the G80 works. It works well and reliable when not abused and the vehicle is in stock form.

Inside the Eaton G80 Locker - YouTube