MPSax

I'm pushing about 600-625 ft lbs of torque on my engine build.
I am curious if you all would be fine running this with a 1969 442 rear end.
8.5" Olds 12 bolt, 3.23 gears, 28 spline

I'm open to upgrading components or is it better to switch over to a Chevy 12 bolt.

Fun71

I recall a factory 1970 W-30 4 speed car broke the original 3.91 carrier at the drag strip using sticky tires. Installed a Chevy 12 bolt with 3.90 gears and didn't have issues.

OLDSter Ralph

If you have 600-625 ft. lbs. of torque, you aren't running a "G block" 400. It isn't "torque" that kills a rear end. Its the sudden application of power to a stationary automobile..."sudden dumping the clutch" with sticky tires that "bite" at 3.000 RPM's and higher.
Every manual transmission (M-21 close ratio) or rear differential I broke was on the starting line at a dragstrip, 3,500 RPM's or higher with drag slicks. If you are running a wide ratio M-20 with street tires, you should be fine.
.......Just my two cents worth. ..

BangScreech4-4-2

If you switch to a Chevy 12-bolt, you'll probably want to eliminate the C-clips.

BangScreech4-4-2

Just out of curiosity, what engine is this build based on?

crossboss

My worthless two cents...
Use a Ford 9 inch. Its not a shame to do so. Drag racers use 'em all the time. Heck, put a fake 12 bolt 'cover' over the back of it and most folks will never know its a Ford rear end.

442Dude

I installed a 12 bolt in mine after the restoration. I have 4.10 gears, Tremec TKX and 575 HP with 600 torque. Love it.

BangScreech4-4-2

Given the differing structures of the two units, I'm wondering how this would be done. Have you seen it before?