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.

 

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.

 

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. ..

 

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

 

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

 

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.

 

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.

 

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

 

Correct- this will not be my G-block. It runs very strong, but not quite enough for my taste. It will be re-sealed, painted and sit in a bag in the garage.
I am building what will be about a 480ci stroker.
I am leaning on seeing how it goes-- being careful not to hook up. Having the original 15' skinny BFGs, already spin with the G block, so I think it might be OK-- just a smoke show until I have the money set aside for something else.

I do like the idea of a Ford 9inch- the made-ready kits from Moser might be the ticket.

 

Thanks Ralph-- I'll be using a TH400

 

Then you have nothing to worry about. If you do happen to twist an axle, you can replace it with a Moser or Dutchman axle. I think you are worrying about something that doesn't need a solution.

 

thanks- just wanted to make sure. Appreciate all the input!