General LSX Automobile Discussion - slowin down
05-22-2012, 06:27 PM
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?
05-22-2012, 07:29 PM
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
05-22-2012, 07:43 PM
No just installed, havent had it at track yet, but there is definite noticeable" seat of the pants" difference
05-22-2012, 07:47 PM
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.
05-22-2012, 08:24 PM
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...
05-22-2012, 10:23 PM
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
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