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Thread: 9 bolt rears
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08-03-2010 #1
9 bolt rears
I've heard different stories about the GM 9 bolt rears. Some people say they are stronger than a 10 bolt and then I hear the exact opposite. I myself had one in my GTA. It had a 383 in it and ran 12.4 @110mph and 11.4 @120 on the spray with a 1.8 60ft. the only thing i had done to it was a set of 3.73 gears because at the time there really wasn't any other upgrades for that rear. I'm curious to know how much power you can put to a 9 bolt thats been built before it lets go. I know there is more of a selection of aftermarket stuff for them now.
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08-04-2010 #2
The 9 bolt is slightly stronger than the 7.5 10 bolt. The 9 bolt used a Borg Warner 4 pinion differential which was quite a bit stronger than the 2 pinion Auburn that was used in the 10 bolt. The axles in the 10 bolt were upgraded to 28 splines fron 26 in '90, but the 9 bolt had 28 spline axles all along. The 9 bolt has bolt in axles where the 10 bolt used c clip axles. The ring gear diameter in the 9 bolt is about 1/4 inch larger than the 7.5 10 bolt, which also add strength. As far as I know there are still no major upgrades for the 9 bolt. You can get a T/A Performance alumunum cover for it, but that's about it.
'69 RS/SS396 pro street/427/4spd/9"
http://rides.webshots.com/album/576443881hfGXxd
http://good-times.webshots.com/album/568860081GZRpyZ
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09-02-2010 #3Registered User
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- Apr 2010
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- Pittsburgh, PA
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hmmm...never heard of a GM 9 bolt...heard of 12 bolt obviously and 10 bolts.... 7.5/7.6, 8.2, 8.5 bolt-in (71-72 skylark/gs/cuttlas) and 8.5 c-clip chevy...
axle tubes were pretty much all 3"' minus s10s and g-bodies which were 2 5/8?
any more info on a 9 bolt? like what car/years did it come out of, and what would it be considered 8.2 or 8.5?
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09-02-2010 #4Registered User
- Join Date
- Apr 2010
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- Pittsburgh, PA
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- 717
n/m did quick google and answered my own questions..7.75 R/P 9 bolt 85ish trans am....cool i guess
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09-02-2010 #5
The 9 bolt is built by Borg Warner and was used in the F body cars from '85 to '89. It has the 7.75 ring gear with 8 ring gear bolts and uses a 4 pinion BW posi with cones. The axles are held in by pressed on axle bearings and bolt on retainers (no c clips). Most of them had disc brakes, but some had drums. A similar differential is used in the '04 to '06 GTO and new Camaro, although these use independant suspension instead of a solid axle.
'69 RS/SS396 pro street/427/4spd/9"
http://rides.webshots.com/album/576443881hfGXxd
http://good-times.webshots.com/album/568860081GZRpyZ
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09-02-2010 #6