I have found a 12 bolt posi. trax. I want to install it in my 72 what exact questions do I need to ask the seller for to make sure it is what I want and will fit my car. It is about 3 1/2 hours from the house or I would drive over to look at. If I can get the info needed I wil drive over an look at it. Just don't want to go by his "It will fit".
Thanks

Ask Him, what year car it came out of, What is the part # on the ring gear. You can research the # and find the ratio and the series of the carrier assy. To be sure it will handle the gears you want to install.
If he has the housing, get the ID. on the right hand tube.
You can run those #'s and be sure it is a 12 bolt.

Ask Him, what year car it came out of, What is the part # on the ring gear. You can research the # and find the ratio and the series of the carrier assy. To be sure it will handle the gears you want to install.
If he has the housing, get the ID. on the right hand tube.
You can run those #'s and be sure it is a 12 bolt.


Many thanks, I will email him now :beers:

Also verify the housing casting number

12 Bolt Housings:

3859140N 1965
3875745N 1966
3894939NF 1967
3917124NF Late 1967
3917124NF 1968
3917124NF Early 1969
3959038NF 1969
3969278NF 1970-1972

I know where your at I just bought a crv code 3.31 ,I talked to the guy a couple times, it also was a pretty good ride to get it.Like the other guys said the info is out there to figure the numbers out.But i dont trust anything i read, so i guess take a few measurements on your car and write them down. Good luck

Make sure it is for your Chevelle. I have looked at a lot of 12 bolts that were "for a Chevelle" that turned out to be from a full sized car.

For a 66, will a 12 bolt from a 68-72 fit as a direct bolt on? or would it need to be a 66-67? Thanks

A 68-72 12 bolt will bolt in but it is an inch wider. Also you may have to swap springs because the saddles are different