axles

[thor]

The difference in a car and truck 12 bolt is the pinion shaft in a 12 bolt is smaller, The pinion shaft in a 12 bolt truck is the same diamerter as the 8.5 10 bolt. So the ring and pinions are not interchangeable. The carrier in a car is also wider. so they don't readily interchange, if you could phisically cram it in there you're going to have to be really creative with the shims.. As for the axles interchanging, How? They are all 30 spline, but there are only 3 sizes of 12 bolt axles on cars, they are...
29 3/4" 64-67 chevelle/67-69 camaro/68- Nova
30 1/8" 68-72 chevelle/70- camaro
31 3/8" caprice/impala
Truck 12 bolt axles are 31 7/16" long so theoretically "Could" fit an impala or caprice, but have a 5 on 5 instead of 5 on 4 3/4" face. Van 12 bolt axles are 33 3/8"

Sorry for the hijack, back to the original question. There are good axles out there that bolt in, but it depends on which car you get. The 8.5 10 bolt is a good axle that will live behind most any streetable combination and comes in a version to fit nearly any gm chasis cheaply... Exception being the 68-72 a bodies as they ran the 8.2 through that whole production run, but 12 bolts were fairly plentiful for them in the early monte carlos.

IMO the 12 bolt and the 8.5 10 bolt are stronger than a 9" in stock form. Before you flame this I will say the ring and pinions in the 9 are better supported, but the axles (yes the 31 spl too) are weak, they are very soft. And for the arguement that race cars use 9"s, yes.... But with aftermarket axles and nodular cases. The 10 and 12 bolts do loose ring and pinions due to deflection of the caps, this is easily and cheaply preventable with the lpw pre-load style aluminum covers. The other downfall with the 10 & 12 bolt is the c-clips, but that really isn't much of a problem in a street car as you'd allready have had some sort of catastrophic problem happening for them to fail.

 

[84gmcjimmy]

Okay cool thanks for all the info. If you don't mind I am going to save this to my computer for when I do get a muscle car

 

[bigblock44k5]

http://www.fourwheeler.com/techarticles/129_0301_axle/index5.html

Also, 4x4 truck axleshafts are 31 9/32" long. 2x4 Axleshafts are 31 5/16. Which makes 4x4's only 3/32 longer than the measurement you have for Impala/Caprice assumming that measurement is correct. 2x4's would be 1/16" shorter. They would work. I aggree that the axles are not going to swap back and forth from any 12 bolt ever made. But there are quite a few that would swap.

Also you can put the thicker car gearset into a truck carrier depending on the gear ratio. Would be the same as using a spacer behind the ring gear which is commonly done.

 

[kennyw]

not to hijack, but what is the difference between a 2wd 12 bolt and a 4wd 12 bolt?

If your talking about axles out of GM trucks, the only difference between 2wd and 4x4 is the bolt pattern for the wheel and the shock mounts. Axle housings and spring perches are identical, but shock mounts are different (only slightly and easy to change with a grinder and welder). I have used 2wd axles in a 4x4 by simply putting the brake drums and axle shafts out of my old axle into the 2wd version. The brakes and axleshafts are identical other than the hole pattern drilled in them.