72 10 bolt Rearend

[Big Jim]

Is the factory 10 bolt 2:73 gear on a 72 Monte the Big 10 bolt?

The code on the factory sheet shows a GW5.

[Mike 57]

Jim,

Check out this link it may be helpful richmond gear

[Sam (Bones)]

Jim, hopefully Alex will pop in here, or PM him, he should be able to help you

[Guest Jabo]

My 72 has a 12 bolt 2:73 gear.

What is a preferred ratio if I go with a 700r tranny behind my 383 stroker?

 

Jabo

[Ian]

Jabo it depends on what you are going to use it for, but when I get around to putting my 700R4 behind the big block, I plan on 3.42's in my 12 bolt.

 

Ian

[72MC]

First to Bigg Jim's question. The "big 10 bolt" if you will, is the Pontiac version of the BOP 10 bolt rear. It has the half moon cut outs in the cover at the 9 and 3 o'clock position. Probably the strongest of the GM 10 bolts.

 

Secondly, any of you guys running an overdrive tranny should really consider running 4 series gears. I originally set up my rear with 3.31 in a 12 bolt behind a 4l80. With a strong engine the gears seems to be to high in overdrive. I recently bought a set of series 3 carrier 4.10 gears to install once I am back from Galveston/Houston in a couple weeks. In overdrive, the ratio is like 3.08's on the highway. Best of both worlds, stop light to stop light and good highway rpm's. - Dave

[Guest Jabo]

Hi Guys,

I came back to this older post because I'm still trying to learn how to manuver around in the chat forum. Tough being a rooky!!!

I was looking for a replacement drivers door hinge when I found a 72 parts car with a full running gear still under it. It has a 10 bolt differential where my car has the 12 bolt. The gears and axials in this parts car are in great shape. My question is; are gears and axials interchangable between 10 and 12 bolt differentials. I counted 41 teeth on the ring gear but couldn't really see the pinion that well. Can you determine the gear ratio from just knowing the ring gear count?

Another question I have is; does the stock 72 Monte driveshaft spline up with a 700R tranny? I will get the driveshaft off this parts car so I can keep mine uncut when I change to the 700R tranny.

I did get a like new hinge off the car. That was real easy since the fenders were already missing. I've never pulled a fender off my car however I understand that's probably the best way to change out the hinge. Don't know which would be the most risky, removing the fender or removing the door. I can see that trying to make the hinge adjustments with the door on the car won't be fun. Thanks to everyone for the tips.

Jabo

[monte70car]

jabo the gears and axles are not interchangeable between the 10 and 12 bolt. the 12 bolt uses a bigger ring gear then the 10 bolt. the only way to determine the gear ratio without knowing the pinion gear is to hold one tire while turning the other and count how many times the drive shaft turns. most likely it will be a 2 something rear end. if the drive shaft on the 72 monte is a 350 it will fit. if its a 400 trans the yoke will need to be replaced. depending on the tail shaft of the two trans you might not have to cut the drive shaft at all.

[alex's72fgmc]

the gear ratio is stamped on the ring gear you just need to do a little math. 41 divided into what the other number is. the options for the different rear axle housing just varied with what they had on the line at the time

 

Corporate 10 bolt or the Buick, Olds, Pontiac aka bop rear end. as long as it is the same length flange to flange on the backing plate and the control arm mounts are in the same spot it will work.

 

if you have any questions pm me and i will get back to you