12 Bolt vs 10 Bolt Rear

[Dan Fahey]

Originally Posted by impstocker

Dan
Isn't that a 7.5 inch 10 bolt in the Impalas. ? I had to run Pro Gears in my 68 Impala, broke street gears, but then again a 4000 l b BBC stick car at that point. Running same 4:88's in my 65 automativ car.

Will Lamprecht
65 Impala 396/325

Camaro’s and Firebirds got that rear.
B-body’s got the 8.5 inch rear.
None of us in the Impala club are having problems.
Unless they are using a Stick.

Chipper brought up that the 8.5 rear uses the same bearings as a 12 Bolt.
That makes it stout.
Wonder if a 12 bolt ring and gear and Spool will fit in a 8.5 Pumpkin?

[Dan Fahey]

Still trying to figure out the best gear ratio.
Using 4.56s with a 4L60E trans.
Not using the locking converter now.
Looking at 5.38’s and locking it up in high gear.
I can program that in the PCM...

Hope to get close to the K/SA index with current cam.

[Mark Yacavone]

Originally Posted by Dan Fahey

Camaro’s and Firebirds got that rear.
B-body’s got the 8.5 inch rear.

Not correct.
The Impala SS may have all come with the 8.5.


Pinion bearings and flange are different, for one thing.
8.5 and 12 bolt take different side shims.

[Dan Fahey]

Originally Posted by Mark Yacavone

Not correct.
The Impala SS may have all come with the 8.5.


Pinion bearings and flange are different, for one thing.
8.5 and 12 bolt take different side shims.

The 91-96 B-boys are the Caprices, Impalas, Roadmaster and Caddy’s.
All were 10 bolt 8.5 rear

Camaro/FB all came with smaller 7.2 rear.
They can surprisingly survive with a good bit of power too..!

About a $1k less to beef up a 10 bolt than installing a prepared 12 bolt unit.
They make them to fit our B-body.
Interesting being the same suspension configurations as the early Chevelles, GTO, Cutlass, GTX.

D

[Rick Schilling]

Generally the B bodies with the Baby LT-1 or 305 have the smaller rear. The LT-1's generally have the 8.5 (Impala and Caprice).

[ss3011]

The later F-Bodies got a beefed up 7.5 rearend , with a bigger 7 5/8" ring gear .

[Mark Yacavone]

Originally Posted by Rick Schilling

Generally the B bodies with the Baby LT-1 or 305 have the smaller rear. The LT-1's generally have the 8.5 (Impala and Caprice).

Shhhh..Don't tell Dan. He's spent too much time on the SS forum, and not under those cars.
Whatever you do , don't tell him the early Chevelles did not have the same suspension. Although it looks similar, it is not a metric configuration.
Also , I have never seen a bolt in 12 bolt for those cars. Maybe those SS guys can help him. Apparently we are not qualified here.

[Dan Fahey]

Originally Posted by Mark Yacavone

Shhhh..Don't tell Dan. He's spent too much time on the SS forum, and not under those cars.
Whatever you do , don't tell him the early Chevelles did not have the same suspension. Although it looks similar, it is not a metric configuration.
Also , I have never seen a bolt in 12 bolt for those cars. Maybe those SS guys can help him. Apparently we are not qualified here.

You are right again....bluster blossom...
I am not under my car often...and that is a good thing!
and It helps to have a Forum to share experiences!

Mark you car is so slow.
It’s shadow waits for you at the end of the strip !

Dan

[MR DERBY CITY]

If Dan runs K SA and if I have figured his combo correctly at 299 HP the total weight including driver is 4055 lbs. I sure hope that 8.5 is as durable as a 12 bolt.

[Mark Yacavone]

Originally Posted by Dan Fahey

You are right again....bluster blossom...
I am not under my car often...and that is a good thing!
and It helps to have a Forum to share experiences!

Mark you car is so slow.
It’s shadow waits for you at the end of the strip !

Dan

Wrong again . I don't own a race car.