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Author Topic:   Changing 7.5 Rear End to 8.5?
busch17
Dirt Roller

Total posts: 19
posted January 25, 2001 11:47 PM UIN: 67129301
I have a 85 Monte Carlo that I'm building and I'm taking out the 7.5 rear end and putting in a 8.5 from a 1977 Monte. What do I all need to change to make this fit? Please help. Thanks!!!!!!

BK19
Dirt Forum Racer

Total posts: 97
posted January 26, 2001 05:58 AM UIN: 40696038
you need to shorten the upper mounts and make new shock brackets. but my local chassis builder has a jig he puts it in he uses the old mounts off the metric rearend welds them on the 8.5 rearend and uses DOM tubing for the upper mounts he charged $75.00 dollars i would check your local builders to see if they do that i hope that helped a little

Pit Bull
Dirt Full Roller

Total posts: 42
posted January 26, 2001 09:06 AM
I did this in my car last season, and it worked out great. All I did was lengthen the bottom control arms approx. 1 inch and shorten the upper ones approx. 1.5 inch. This will probably vary a bit for your application. Just move it around until the punion is just about level with the frame, maybe slightly upward. You could even build yourself some trick control arms out of some rectangle tubing. This will help prevent axle hop and come off the corner better. Im going to build some for mine this season. Oh - one suggestion about the 10 bolt - keep at the very least a FULL gallon of fluid in it, and use good synthetic fluid to help it run cooler. Just jack up the right hand side of the car so you can overfill the pumpkin. The main reason you do this is to keep the fluid in the pumkin where it belongs when you turn left. Lots of people bash the 10 bolt saying its weak and can break on a rough track, but ive had no trouble with mine. Good luch in 2001, and have fun!

junebug
Dirt Maniac

Total posts: 132
posted February 22, 2001 03:10 PM
will your rules not allow the use of a 9" ford busch17

busch17
Dirt Roller

Total posts: 19
posted February 23, 2001 11:43 AM UIN: 67129301
Hey Junbug I can't use the Ford 9". My rules state GM parts in GM cars. So I can't use the Ford 9"

Pit Bull
Dirt Full Roller

Total posts: 42
posted February 23, 2001 06:44 PM
Oh yeah one more tip I just heard about the 10 bolt axles. MAKE SURE you have the axle shafts magnafluxed for cracks BEFORE you run them. Ive seen many axleshafts that have cracks just outside the bearing race, and snap and put the car on its lid. Hope this helps...

racer17j
Dirt Maniac

Total posts: 165
posted March 06, 2001 02:53 AM UIN: 54865418
the bottom arms should fit and the tops just drill a hole 7/8 in in front of center of the old one should slide right in

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