Ric

I used to be a big Mopar nut, and I remember the 742 and 489 casting of the 8 3/4" axle having ridiculously huge pinion shafts... 1.75" for the 743, and 1.875" tapered to 1.75" on the 489. They're set up like the 9" Ford, using a removable 3rd member and whatnot. They don't have near the hypoid offset as the 9" though, which should make them more efficient. However, they don't have the 3rd bearing, either. Any strength that would be lost to that is made up with the behemoth pinion shaft sizes(which I might add are larger than a Dana 60 pinion). Is there any reason why this axle wouldn't be a good candidate for swapping into an F-body?

Please, let's keep it factual, not the same "Just get a 12-bolt!" crap. Not bi_ching or anything, I'd just like to know why it wouldn't work.

Ric

Anyone? Hello???

1999Z28

torque arm

Ric

It can be set up like a Ford 9". The 3rd member comes out of the housing just like a 9".

blky2k2z

iTrader: (2)

have a chassis shop or a circle track shop make torque arm brackets for the 8 3/4. ne thing can be done as long as you put your mind to it or someone elses.

blky2k2z

iTrader: (2)

back in the early 70's the door slamers actually used 8 3/4 rears due to the fact of thicker axle tubes. this was before they started making fabricated rear housing.

cam

iTrader: (9)

The 8 3/4 isnt a bad diff but parts are more costly and castings are WAY old now as it has been out of use for some time. It aint light either and its not overly efficient. Unless you have sweet core and gears and a new posi sitting around I could think of no good reason to set out and build one when for less dough you could do a Ford and have a hella lot more carrier/gear options.

Ric

I see. I just hear a lot of people on here griping about the 9" not being too efficient, and wondered if the 8 3/4" could be an answer to that without sacrificing strength.

Hugh betcha

iTrader: (1)

I bracket raced a 70 Cuda with the 8 & 3/4 rear end. The car is now restored back to original and the rear end is still quiet. Your challenge would be getting brackets and torque arm provisions mounted properly. Not to mention the ABS system function, and bolt patterns for your wheels. Strange now has a Dana 60 (Model S 60 ) for F body cars. This is the 9 & 3/4 inch series installed in 1970s Hemi cars. I would bet one of our sponsors that handle Strange, could elaborate.

Hot Wire

I have one in my car

https://ls1tech.com/forums/gears-axles/455986-8-3-4-rearend.html

Ric

That's some good stuff, there.

blky2k2z

iTrader: (2)

or you could do the 9" housing with the alum. center section that uses the more effecient gm 12 bolt gear setup and itll be lighter than anything around!