12 Bolt Rear End Gear Locker?

[GMCStepper76]

Hello Guys,

I have a mystery on my hands. My buddy and I were cleaning all our old axle housings and sheet metal, old frames etc. to go to scrap yard. My buddy’s son in law is restoring a 76 Toyota Land cruiser FJ40. He has a bunch of old axle housings to Frankenstein good ones for his rig.

While moving the "old" ones to the scrap piles my buddy and I noticed one of the rear ends seemed like a locker (both wheels rolled, stop one wheel the other stopped immediately) So we decided to pull the cover. Now I know it’s a GM axle housing made to go under the FJ40. The axles are obviously shorter. The housing is marked clearly GM. It’s a 12 bolt housing (exact same on my 76 GMC K15)

So we opened it up and there was a BRAND NEW differential. No gear oil had ever been put in housing. The yellow assembly grease was still on the ring and pinion teeth. Also it looks like a locker to us. There are 2 square blocks (thrust blocks) that slide on the pinion shaft. There are no spider gears or limited slip packs (sorry if that’s wrong terminology) The back of the diff carrier is clearly marked GM with a bunch of other numbers (sorry didn’t write em down) On the side of the ring gear it is marked GM-12  4.11 stamped in it!

I have looked in my Chilton book and can only find very basic info.  We took out the locks screw, pulled the pinion shaft out. Pushed the axles in, C-clamps came right off. Took out the axles. Then we took out the caps holding the diff in the carrier, removed yoke to pinion nut, popped out the pinion. Everything is BRAND NEW. It’s never been run. Looks clean as a whistle.

Now after all that, what do I have? Is it worth anything? Will it work in my 76 GMC K15 shortbed (as long as ratios match...right?)

Can anyone please shed some light? I have everything carefully wrapped up and in a cardboard box. I was able to get everything out except the races. Even the yoke looks brand new.

Thanks in advance guys. I appreciate the help.

[dvdswan]

I'm guessing its the pinion races that you couldn't get out.  if that is the case you can pick up new races for your install.  me personally like to know that the race and bearing are a set. 

if it is indeed a 12 bolt it should drop right in with your current 12 bolt axle.  yes, you want 4.11/4.10s in the front so they match.  if you have a 205 t/case you can install the carrier and gears now, just don't use 4wd or pull the front driveline out or don't lock your hubs so you can't.

IDK if the car 12 bolt is different from a truck 12 bolt but wouldn't think so.

[Captkaos]

I would need to see what you are describing.

A 12 bolt car is NOT the same as a 12 bolt truck...  Other than the number of bolts on the cover.

[dvdswan]

A 12 bolt car is NOT the same as a 12 bolt truck...  Other than the number of bolts on the cover.

that's good to know.