[pablo]

yeah they do 700+ whp through this transmission and the F23 and F35 variants.

I thought the F35 was having problems with cases breaking at a lot less than 700whp? Like closer to 400whp. That's what's got me concerned about the F40, because it is so close to the F35. The OEM Quaife in the Cobalt interchanges with the F40, so a high quality LSD is available.

I've got an F40 on the shelf, I bought it years ago when they changed the gear ratios in 07 and blew out the 06's. I don't see why it wouldn't be an option for the 3S since an adapter plate would be needed to an EA or EB also. The F40 is narrower than the E153 so other than all the custom work, it should be doable.

 

[pablo]

I though the EA / EB did bolt to the 3s without an adapter plate?

I heard the F35 had cracking issues too, and the F23 was actually stronger than it, but I did not hear anything bad on the F40. Either way, It is cheap for a brand new transmission!

The EA uses an adapter plate in the Lotus to mate to the 2GR. So bolting it to a 3S wouldn't be difficult since there is a part being produced. But there is still an adapter plate. The EA trans is also used in the Mazdaspeed3 and the Mitsubishi Eclipse with the 3.8L V6.

I haven't heard anything bad about the F40 either, but I've only seen it used in a few Fieros, and judging by the body kits and 20's on the cars, I don't think they ever planned on putting a lot of power through them. For example, supercharged LS7:

If you read the thread, I think the gears were micropolished and cryo treated. But with that much power, and a less than ideal chassis setup, breaking the tires loose at the first blip of the throttle really doesn't do much to test the limits of the trans, since as soon as the tires slip the gearbox is seeing a lot less load.

I'd have to find the threads on the Cobalt F35 again, but IIRC(and this was a lot of years ago that I bought the F40), the F35's were cracking at where the intermediate shaft is mounted in the case, on the bellhousing side. And I think it was happening with stock power levels when people were launching the cars hard. I seem to remember the webbing in the trans to be pretty close between the two transmissions as well.

I'm not saying not to use the transmission, but if I were planning on putting a lot of power through it, I'd have a plan B in case the transmission just isn't up to the task. At $400 you could just buy a few transmissions and replace when necessary, but I would rather overbuild everything and never work on it again.