rear end ???

[sparkie]

1)I found a 12 bolt 303 posi from an old impala. Will it fit in my 81 g-body? Am I limited to a certain size gear with that carrier?
2) Will a rear out of a 71 monte or 60's el camino fit my 81?
If so, will a 8.5 posi unit out of a IROC fit either of these rears?

I found a yard that has these items and would like to make something work for me.
Thanks

 

[equalizer442]

no, no, and irocs never had 8.5s

 

[onefastjackass]

Why would you worry about putting a twelve bolt in in the first place.The aftermarket make almost bullitproof parts for our rerarends.And the ring gear in a twelve bolt is not that much bigger then an 8.5.

In my opinion if you already have an 8.5 keep it upgrade it if necessary unless you start running in the 9 second range then think about going with a built 9 inch.

Changing it just to say I have a twelve bolt is pointless.Unless you don't have an 8.5 and then I say go ahead and put in a nine inch now then you will not outgrow it.

 

[b4black]

He has a 1981. No 8.5" there.

The best rear that will bolt in place of your 7.5" is a 8.5" from a 1984/87 Turbo Regal or HO/442. Expect to pay $750+ for a complete, limited slip 8.5" rear.

 

[Red Regal T]

Perhaps you mean an 8.5 out of an earlier z-28. Those were leaf spring cars. I think you're stuck with finding an 8.5 G-body rear. You can get one for around $600.

 

[GNVAIR]

With any G body, you dont have too many options of bolt in rears except the 8.5 10 bolt from a GN/442 as others mentioned.
To install a 65-72 10/12 bolt requires a SSM (south Side Machine) kit and requires welding of spring perches and lower shock mounts as well as rims with more back spacing since the rear is wider. This is on top of the $600+ cost of a 12 bolt.
You can buy a brand new bolt in Moser 12 bolt complete for approx $2k or a bolt in Ford 9" for about the same price.
Leaf sprung rears will not work and neither will 73-77 A body rears or 77-96 B body rears. Its an unfortunate thing, but if you want to go fast with a G body, its one area of the car that requires spending some money.

 

[turbofish38]

If done properly an older 10 or 12 bolt from a GM A-body can be a bolt in with the right kit. For example I have a 8.5 from an 72 Skylark in my GN right now and with the special wheels and some junkyard scrounging I have about $600 invested. Agreeing with everyone else posting here the best bet would be to spend the money for a TR rear. Eric Fisher

 

[GNVAIR]

Originally posted by turbofish38
If done properly an older 10 or 12 bolt from a GM A-body can be a bolt in with the right kit. For example I have a 8.5 from an 72 Skylark in my GN right now and with the special wheels and some junkyard scrounging I have about $600 invested. Agreeing with everyone else posting here the best bet would be to spend the money for a TR rear. Eric Fisher

There is no such thing as a "bolt in" early 10 or 12 bolt. The coil spring perches are in the wrong spots and the lower shock mounts must either be bent to gain the correct angle on the shock or cut off a replaced with the piece SSM supplies in their kit.
Remember, the SSM kit is approx $300 alone and that is before you buy a rear. Then there are the other issues of brakes, driveshaft and wheels. So it can get expensive very quickly.

 

[turbofish38]

The SSM kit is IMO a race only piece. I used the kit from hpmotorsports.com which at the time about 10 years ago went for $200. Yes you do have to cut the spring perches and weld new perches and shock mounts which to those of us without the equipment and welding skills would not qualify as a bolt in. I was just stating it can be done if you have the resources. It would have just probally been easier to say "if you have to ask you shouldn't be doing it" Eric

 

[sparkie]

Thanks for the info. Appreciate it!
I gues I am back to the drawing board.