I have a 1972 Cutlass Supreme. I'm looking to change it to a positraction rear end. Can somebody help me with my options on how to go about doing this?

 

You need to change the carrier to posi. You will need to re-shim for proper gear contact too.
2 of the best guys on this site that work on rears own their own businesses. Get in touch with one of these guys:
Jim Mitschke (Monzaz) see JD Race & associates http://www.jdrace.com/
Brian Trick (507OLDS) thetrickfamily@yahoo.com

They are both experts, and really nice to talk to also.

 

http://www.chevelles.com/forums/showthread.php?t=391212

You can convert your current rear end into a posi unit,if the current carrier is close to the gear set you want...3.08 are pretty common,which means you can go as high as 4.10 gearing,if you like.
I've been looking for posi rear ends,and they seem to run about $900-$1200 rebuilt and ready to go.
it's not hard to swap out the rear end..figure about 4 hours if working alone.
If your lucky,you may find one used for about $500.

 

I was watching Stacy David's Gears once and he put a "locker" in the rear of some car in about 5 min. Is that an option? How does that work? Does it change whatever rear you have to a posi?

 

Stacey David took more than 5 minutes. They edit down the production time to meet show's time frame.

Nasty: That's why I suggested he contact Jim or Brian. I got an OEM series 2 posi reconditioned with the bearings already pressed on from Jim for around 360 - shipped.

Brian can also score some great deals on carriers - it just depends on what you want and what the application is for.

 

LOL... It's TV guys. They have to fit it in a 1/2" to 1 hour program. They NEVER show what your really needing to know.

 

OK, glad I could make you guys laugh but I was just looking for a little explanation on lockers for rear differentials. I too have heard how it takes time, special tools, shims and knowledge to set up a rear diff. I also know how television works. I thought someone would just say something like " lockers work this way.... and you cant do them with all types of rears" or "to do a Chevy its this way and an Olds is this way" or " a locker works this way and a limited slip works this way" I am gonna try and post a link to the episode I watched and maybe you guys can give your opinions on it. First off, I know its a Chevy and that may be all that needs to be said? Is there such a thing for Oldsmobiles? I have no idea but am just looking to learn.
If the link doesn't work go to youtube and search Stacey David's knuckle Buster (part 2) (S3 Ep. 2-4) Locker install. Here is the link:

 

A locker might not be the best choice for a daily driven street car. You might be better off finding a used Olds or Chevelle rear end with limited slip. Generally speaking you can replace the bearings and brakes and be ready to go if the diff isn't trashed.

 

I bought Chevy 12 bolt 3:55 posi from Wayne Jack Auto Service in Johnstown, PA. Just installed this past weekend. Very happy so far.

 

There are many ways to go about getting posi

Power trax / Spartan locker etc. will install into your OPEN NON POSI carrier to give you both tires spinning with minimal extra tools needed... And you can use the gear ratio you have already in the rear.

You would just need to ID the rear you have 10 bolt 12 bolt and or size and make. Then see if they make one for that rear.

Posi units such as Eaton Auburn True trac etc will require you to set the ring and pinion back up upon installand also give you a less noisey smoother alternative... These are the type of unit a Original car optioned with Limited slip will use.

Then there is the POOR MAN posi - Mini Spool

And finally the lazy man locker - WELD THE SPIDERS.

Hope some of this info helps If you are serious about purchasing anything I will certainly take the time to help get you a unit that will fit your needs. Jim

 

the 8.5 and 12 bolt are about the same in strength usage by the way and use a posi the gears plus that good used parts i mean around 300 average just check around.