10 Bolt v. 12 Bolt
 

I'm sure this topic has been covered a million times, but my poor searching techniques haven't been able to find an answer to my question.

I have a 1971, C10 with leaf springs and a 10 bolt rear end. The engine is a 350, slightly warmed. It currently has a TH400, but I'm debating changing it to a 700R4. With that in mind, is there any reason (aside from the fact that a 12 bolt is much more durable) that I should change the rear end if the one I have is good? Some people have said that the 10 bolt is too weak for my motor. Can that be true? That's what came from the factory. If I do change it, what can be used as a donor? Thanks!

Re: 10 Bolt v. 12 Bolt
 

I had a 10 bolt behind a 350 hp SS El Camino....it held fine for years. I doubt you'd have any trouble with it but you might have it checked anyway just in case. Personally I see no reason to change it if the gears are good.

Re: 10 Bolt v. 12 Bolt
 

I'm wondering who went through the trouble of putting a weak axle in your truck.
They never came with 10 bolt rears

Re: 10 Bolt v. 12 Bolt
 

Theres a few different 10 bolts.. some would hold up fine like the 8.5 and 8.2, but if you have the 7.2 or 7.5 ring gear Id be a little leary.
Heres a link to help you

http://www.maliburacing.com/rearend_guide.html

Re: 10 Bolt v. 12 Bolt
 

do you have a pic of the axle?

Re: 10 Bolt v. 12 Bolt
 

Here's a photo of the rear end.

Re: 10 Bolt v. 12 Bolt
 

yep, basic chevy 10-bolt. Don't know the ring size though.

I say run it till it breaks... why fix what's working.

If you decide that you don't like the gearing then keep your eye out for a 12 bolt posi unit...may pay $300-400 for a decent one.

I sold an open 12 bolt for $50 cause I was tired of hauling it around.

Re: 10 Bolt v. 12 Bolt
 

Looks like an 8.5. See the ears below the cover? Ring gear diameter is close enough to the 12 bolt to not make a difference. The pinion diameter is larger than the 12 truck (same as 12 car) The ring gear bolts are reverse threaded and larger in diameter than the 12 bolts, so that's a push. Only short coming is 28 spline axles if the rear is pre 88. Later model 8.5's are every bit equal to a 12 bolt truck.