Benefit of a spool vs posi?
Benefit of a spool vs posi? I'm getting ready to purchase a rear for my M6 car....I was set on a posi 12-bolt, 33 splines, etc, but was told (Justin- 2MuchRice and a few others) that I'd benefit from a 9" w/ spool even more. It's for a street car to see some track use. I know 9"s are heavier, stronger, and and have more drivetrain loss, but what else should I factor in to make my decision?
On an everyday car I would stick with a posi if it were me. My original 33spline 12 bolt eaton I bought a year ago and put over 200 dragstrip passes on dumping the clutch at the rev limiter with slicks is still surviving in a friends heavy WS6 that runs low 7s with a M6. Gear is noisy (3.90) but its had a hard life and its still going. Some guys blow up the 33 spline eaton 12 bolts though so its more then possible.
OTOH you will most likely never break a 9"/35 spline spool no matter what you do. Its a good feeling when you are at the track to know you can dump the clutch whenever and never have to worry one bit about it breaking - I was never that confident with 12 bolt/posi. You can try the spool and if you dont like it you can always switch to a 35 spline locker down the road.
If you daily drive in the rain/snow I wouldnt use a spool though. A 9" has a lot more gear options but will cost you some power. Its a tough decision. If you have 3 channel ABS and you want to keep it you only have one choice though, 12 bolt, if you want a bolt-in setup.
Its a tough decision but it reall depends on what you will do in the future with the car, if you think it may turn more and more into a race car get the 9" right off the bat IMO.
OTOH you will most likely never break a 9"/35 spline spool no matter what you do. Its a good feeling when you are at the track to know you can dump the clutch whenever and never have to worry one bit about it breaking - I was never that confident with 12 bolt/posi. You can try the spool and if you dont like it you can always switch to a 35 spline locker down the road.
If you daily drive in the rain/snow I wouldnt use a spool though. A 9" has a lot more gear options but will cost you some power. Its a tough decision. If you have 3 channel ABS and you want to keep it you only have one choice though, 12 bolt, if you want a bolt-in setup.
Its a tough decision but it reall depends on what you will do in the future with the car, if you think it may turn more and more into a race car get the 9" right off the bat IMO.
11 & 7 Second Clubs
Joined: Oct 2004
Posts: 1,299
Likes: 0
From: Motorhome, Freeways, Truckstops, Pits
Originally Posted by Pimpium57
I'm getting ready to purchase a rear for my M6 car....I was set on a posi 12-bolt, 33 splines, etc, but was told (Justin- 2MuchRice and a few others) that I'd benefit from a 9" w/ spool even more. It's for a street car to see some track use. I know 9"s are heavier, stronger, and and have more drivetrain loss, but what else should I factor in to make my decision?
Last edited by bickelfirebird; Mar 17, 2005 at 04:07 PM.
Teching In
Joined: Oct 2004
Posts: 36
Likes: 0
From: Wisconsin
I have blown the spiders in my 12 bolt, foot braking. 3500#'s 11.50's.
BBC chevelle, I called eaton and moroso and was told by both I would probably break their's also. So It is spool for me, no problems since. Also I drive it on the street all the time, and run 30x12.50 et streets. No probs, just wouldn't call the spool "daily driver friendly" where it would see rain/snow etc.
BBC chevelle, I called eaton and moroso and was told by both I would probably break their's also. So It is spool for me, no problems since. Also I drive it on the street all the time, and run 30x12.50 et streets. No probs, just wouldn't call the spool "daily driver friendly" where it would see rain/snow etc.
