8.5 10 bolt ...need more info..

[Krazy Kracker]

Been debating on what rear end to go with. Heard 12 bolts are out...Ford 9" is the best,but not just a bolt in. For now until I can build one up from scratch, everyone keeps mentioning the 8.5 out of some "special" GM cars -IE Grand National, Monte Carlo SS . What years and models would I be searching for? Will these bolt right when I drop the 7.5? Anyone got one laying around, and willing to part with it,please let me know. Thank you

 

[lilbowtie]

They make a bolt-in - mine in a Moser

 

[Kansas Bu Wagon]

Monte ss had a 7.5.

8.5's came in GN's, T-Types, hurst olds, and I think 442's. but not all were posi or had desirable gears like 3.42 or 3.73. So know what you're buying.

 

[Krazy Kracker]

They make a bolt-in - mine in a Moser

Currie has a bolt in also,that was gonna be the "Winter Project". But for now I was gonna try to pop that 8.5 in it if I could find one.

 

[Krazy Kracker]

Monte ss had a 7.5.

8.5's came in GN's, T-Types, hurst olds, and I think 442's. but not all were posi or had desirable gears like 3.42 or 3.73. So know what you're buying.

so ..any 80"s models will work? Even if its not posi, to get the 8.5 would be a good start.

 

[Kansas Bu Wagon]

Yeah as long as its out of a g-body. I paid $400 for mine with a broken axle, mini spool, and 4.56 gears. It's sitting in the shed until I have money for a posi, moser axles and different gears.

Can you tell the difference between an 8.5 and a 7.5? If not I can get some pics of mine so you don't accidentally buy a 7.5 lol.

 

[Fox80]

I have also been looking into this, I think I would go the Moser route. The money that guys get for a bare 8.5 housing is nuts, and when your all done you still have a GM c-clip axle that is prone to failure with good power. I looked into a Moser for $1,800 you can have a 9" with disc brakes and parking brake, and powder coated. I build gears myself all the time so building a center section is no big deal. I think I could be all done for around $2,400 with a locker and quality set of gears. Granted u won't have quite that much in a 8.5 but when your all done you will have a drum brake weaker rear-end. Lilbowtie did you use Moser brakes? Were you able to use the factory parking brake cable?

 

[galeaiii]

I went with the 8.5 from a 442. It literally took me by myself about 1 hr to bolt it in and about another half hr for me and someone else to bleed the brakes. I found one for $1000, sold my original rear end for $700, then put $700 in the 8.5 fully rebuilt and powder coated. As far as the disc brakes go, my 7.5 had them on it (very easy to do and the parts are cheap enough) the 8.5 is drum and I honestly can't tell a difference in the stoping power. The same disc brake swap that works on the 7.5 rear will work on the 8.5 rear. Both my old rear and the new are 3.73 posi, the 8.5 feels a lot different (in a good way) I believe it's the different posi units. Unless you plan on running some crazy HP and or torq the 8.5 will be fine. There are GN's that have at or near 1000 hp that run these with no problems, of course they change the axles and posi units but like I said they are fine for what the average person needs with a rebuild. I believe Tobyp has one from a 442 that is a 3.73 posi for sale, look him up. Here's mine, completely a stock rebuild.

 

[jpoole]

I have a 10 bolt 8.5 posi 3.73 coming for my 83 Hurst, does the drive shaft need shorting to install this one in place of my 7.5 10 bolt?

 

[spidereyes455]

I have a 10 bolt 8.5 posi 3.73 coming for my 83 Hurst, does the drive shaft need shorting to install this one in place of my 7.5 10 bolt?

Yes the 8.5 rear uses a driveshaft that is about 1 inch shorter than the 7.5 rear. It's always a good idea to try and get the matching driveshaft when you buy an 8.5 rear.