towerhand

installed a 9 inch rear in my car with 3.89 richmond gears and a spool with 31 spline axles. I had a stocker with 3.73 gears. My car is a 02 ws6 m6. Seems like the car slowed considerably with the new rear, sounds crazy, i know, but does the 9 have that much more rotating weight and mass to cause this?

Prorac1

iTrader: (4)

No, not usually. Is this "feeling" seat of the pants, or do you have some track times to back this up. Report back with track times and let us know. Eric L

towerhand

No just installed, havent had it at track yet, but there is definite noticeable" seat of the pants" difference

senicalj4579

iTrader: (41)

I believe it no doubt. If your anything like me then you know your car just like its attached to your body. Call me crazy but I could tell the difference after taking the back seats out of my car and its only 30lbs.

pewter2002

iTrader: (4)

OP may be on to something. The 9" has more parasitic drag than a 12 bolt. I am not sure how noticeable it is though. Chevy High Power or GM High Tech did a test that included these two rears and maybe a couple of others too. My memory is that the 9" had the most loss through it by a large margin. Obviously it is very strong so it is a good choice, can't remember how the 12 bolt compares to it strength-wise...

Prorac1

iTrader: (4)

Yes, because of the offset pinion, the 9" has the most parasitic loss. Acording to the article that Jeff Smith did in chevy hi performance, the 9 inch had a 10 hp disadvantage compared to the 12 bolt. Eric L