I'm running a Borg Warner 9-bolt or M87 rear end with a rare 3.70 ratio out of a 85 or 86 T/A. Its stronger than a standard 10 bolt, but parts are hard to find, the only place I can find is 9-Bolt.com in Australia and I'd rather not buy parts way down there if I don't have to...if anybody knew of a place I figure someone on here might. I need a pumpkin cover!!! Thanks
http://cgi.ebay.com/ebaymotors/TA-P...emQQimsxZ20090804?IMSfp=TL0908041710001r25236 http://www.drivetrainspe******ts.com/categories/gm/gm-775-9-bolt-borg-warner/
While I understand working with what you've got, don't go too crazy w/ the 9 bolt stuff. It's only stronger than an 80's era F-body 10 bolt. In terms of strength and durability, the old 10 bolts (8.5" models) would walk all over either of the rears from the 80's. Back in the early 90's, I broke a stock 10 bolt in my '88 T/A with the stock, limp noodle 305 FI/700R4 combo- not like that thing was a powerhouse, ya know? I don't mean to discourage you, I'd just hate to see you sink a big wad of cash into a timebomb.
I'm just running a 250 straight six and a bucket doesn't weigh much, so it should be fine, the rear end already has all the coil buckets, brackets and what not welded on so...I didn't even know there even was a nine bolt until i grabbed a 10 bolt cover off of a buddies rear end and tried to bolt it up. I had to count the holes twice, I didn't know what the hell the deal was until I did some research. It was sorta funny
I have the same rear going behind an pontiac 455/NP440 in my 50 chevy. 3.45 gears, posi. I don't plan on dragging it, and i'll be running street tires, so i think that rear will last forever. Some love it, some hate it. Time will tell.
Good luck with that one... Even if it is a smogged up 75 455, the torque the 455's make will make that rear **** it's pants. Do yourself a favor, locate a 1st or early 2nd Gen F body rear or a Nova rear and do it once, do it right and get it over with... They are the perfect width for a 49-52 Chevy. The 9 bolt diff's are not all they are cracked up to be if you are running anything over the stock motor they came with. I blew up the one in my IROC twice before I located a dana axle for it from a turbo T/A. Don't get me wrong, I'm not trying to be a nay-sayer, just save you from being stranded with your ring gear laying on the ground. I blew up a 3.55 geared 69' Camaro 12 bolt posi that I had under my 69' Firebird convertible running a stock 70' 455/M21 on street tires. The 455's are torque monsters... My motor was rated 365 hp, 510 ft. lbs and literally twisted the body to the point where you couldn't open the door unless you put the car in reverse and gave it a goose...
Perhaps, but then i'll lose my rear disc setup or pay tons of $$$ to convert a rear to it, make it posi, gears i want, etc. If i'm gonna drop that cash, i'll get a moser 9 bolt. But until it gives me trouble, i'll run it. Some have had no trouble doing terrible things to them in the cars they came in. my car is lighter and i'll be taking care of her, and the rear was rebuild by a pro. I still bet it holds. It's like guys saying you can't run a saginaw with a powerful motor. But then you see a guy doing it no problem!
I know this is old but it might help someone, check out 9bolt.com sldo this guy had adapters and kits for huge late model brakes for that rear and others, just got a set of his plates to install the PBR rear disc off my 7.65 in my B4C camaro onto a early 9 bolt rear Im installing. Its nice heavy duty stuff. http://www.flynbye.com/
The M78 9 bolts (or BW78 in Australia) are reasonably strong factory, rated at 220KW (295 HP), as long as they are set up properly. They can handle up to 400 HP easily with a couple of aftermarket parts. If you can get a 4 spider version you'll be a happy lad. After being quoted about $5,000 to buy and set up a 9 inch, the diff guy I use said my Borg Warner will be fine for street / light racing, at around a third of the cost to set up for triangulated 4 link. I'm not running huge HP at the moment, and want some handling. The site Jim_Rockford007 has linked too does have some good basic info. http://www.9bolt.com/technical.html Here is another: https://www.streetmachine.com.au/features/1705/borgwarner-diff-conversions-tech-talk
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