Automatic Transmission - flywheel weight ??'s




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JL ws-6
12-06-2005, 02:18 PM
I'm looking to do a M6 to Th400 swap this spring, and am starting to get pricing and a list of parts together. I wanted to leave my clutch and whatnot together on the flywheel.. so another flywheel is in order. I know on a M6 car, a lighter flywheel will "rob" less Hp and let the motor spin up alot quicker, but not launch as good because of the lack of spinning weight to help get the car moving. Does it work the same way with a auto tranny with a big converter, or the other way around? I'm trying to figure out what to do as far as a flywheel is concerned.. go heavy, like a new stock one, or get a lightweight aluminum one. Another question.. I understand the flexplate, and that has to be heavy duty, probably weighing more then a factory LS1 piece, but what about the flywheel? how much stress does it see? Reason I ask is because if a lighter flywheel would run better at the track and does not see much in the way of a load ( little chance of failure ) I am thinking about going as far as to have an alum one lightened some, really try to get as much out of it as I can.
Anyone has any info on this, please enlighten me. Thanks.


Steve Burger
12-06-2005, 04:04 PM
Flywheel = M6
Flexplate = Auto

They are the same thing for different transmissions if that makes sense. If you convert you will not use a flywheel but will use a flexplate. Having done this swap I can tell you the flexplate is a lot lighter. I would also get a TCI or other SFI flexplate. The factory one looks like sheet metal to me.

JL ws-6
12-07-2005, 04:52 AM
O.K.... this is making a little more sense now. The SFI one was what I planned to use.. but for soem reason I thought that the flexplate was attached to the flywheel........my bad.

The TCI one that summit has listed in the catalog is o.k. then I assume? Anyone out there know of anywhere that's a better price then what Summit's offering?


Steve Burger
12-07-2005, 08:03 AM
Summit is about average. Expect to pay 200.00 give or take. One tip is to clean off the powder coating where bolts will touch metal. Then there is no chance of the bolt getting "loose" because the powdercoating gave way.

JL ws-6
12-07-2005, 09:12 AM
thanks, I'll remember that.