I have a stock 2.56 carrier in my 70SX and picked up a posi carrier, is there anything I need to know to change these out? is there spacers or shims I need to deal with? Should I have a shop replace this for me or is it fairly easy?
Thanks in advance

 

Doug, is it a 2 series carrier? Three and four won't work because you can make a gear thinker with a spacer but you cant make it thinner. That is if you reusing the 2.56s.

 

Look for the 3 large numbers cast between the ribs on the end of the carrier. That ID's the specific carrier.
http://www.supercarsunlimited.com/in...id/diff_id.htm

 

671 3 series 28 spline axles 3.08 -3.23 and aftermarket 3.42-3.90 gears, with spacer 3.42-5.00
673 2 series 28 spline axles 2.56- 2.78 with spacer 3.08 -3.23 and all the aftermarket 3.42 3.90 gears
588 4 series 28 spline axle 3.42 -5.00 ratio
672 4 series 31 spline axle 3.42 -5.00 ratio

these number will be in the webbing check the reference picture of the webbing .

358 2 series open
156 3 series open
359 4 series open THANKS

Jim
J D

 

The posi carrier I have to swap out has 153 on one side and 30153 on the other. Is this compatible?
Thanks in advance.

 

Doug, does that carrier have a 10 or 12-bolt ring gear flange?

 

359 carrier - 3.42& up - open - 31 spline !

 

It has a 12 bolt ring gear flange.

 

Sounds like you have a unit from a fullsize car.That will not fit the 12-bolt O-axle.The O-axle has a 10-bolt ring gear.The O-axle carriers are listed above.

 

Why would they skip around on casting numbers like that? 358 359 I would think 360 or 357 would be in there some where...lol. NOT 156 ...???

 

Hpw many bolts on the cover?

Show us some pictures of the unit. Jim

 

12 bolts on the. cover as well. I will get a pic or two in the next day or two.

 

Jim,
My guess is they already had some sort of casting number with those other digits. Just like 671,672,673,but then 588.

 

Here are a few pics.
Thanks for the help.

 

Fullsize car.Could be 28-spline or 31-spline.Large 12-bolt.Could also be the one with the big 10-bolt cover & 12-bolt ring gear,like the later fullsize wagons had.

 

Brian Is correct on the 12 bolt ring gear with 7/16" left hand thread bolts. 1971-1975-6 era 28 or 31 spline (usually c-clip axles) Fullsize Pontiacs, Olds mobile and even Chevy Impalas used them.
The cover was 10 bolt scalloped on the 3 and 9 o'clock sides (kind of like the Pontiac rear cover or early 10 bolt 8.2 Olds cover) BUT LARGER over all cover ... of coarse)

I have the 153 carrier as holding the 2.73 and 3.08 ratios.

There are NO other housings this carrier will fit into... NO aftermarket gears for this rear (well that is not true ONE 3.55 set Brad at Fabcraft has a set for 450.00)

So hopefully this will give an idea of what you have or do not have. Jim

IT is a EATON unit. Clutch type.

 

Short answer is that you did not get the right posi carrier for your rear end, I think you have the 12-bolt cover Type O rear end. You might be able to sell the posi carrier you have, but only to someone who has one of those cars. Also, Fabcraft might buy it, they bought something similar from me for $75...

Steve

 

Thanks everyone for the help. Very informative group of people we have here.