im doing the research for my turbo 3800 build. im planning to swap in a f40 tranny. anybody have experience with how much power this tranny can handle before it breaks? im planning on at least 500 horses,

also performance wise, is the 4T65E-HD or the f40 better? i plan to autocross my car regularly.

my cars a 88 GT 5-speed getreg, and i really dont want to convert it to a auto.

[This message has been edited by etofun (edited 05-20-2011).]

your car is manual yet you dont want to convert it into a manual? or do you mean you dont want to convert it into an auto??
i heard the F40 can take 300 - 350tq

crap sorry, damn typo. i thought i got them all. do you know if thats the manufactures rating?

edit: just found out that yes it is. the f40 is certified to 295 ft/lbs of torque.

i guess im asking people who have used this tranny with higher horsepower engines.

[This message has been edited by etofun (edited 05-20-2011).]

im curious to know as well. I have a 3800sc and im waiting something a little better than the getrag down the road

I know Archie has used them on several LS swaps and none have failed. Clayton used one on his car as well with a 383 Strocker that was Dynoed at over 550 and almost 600lbs of tq. and both he and I tried to break it. the best we could do was trash the hubs.
this one was stock no mods. the one I plan to use in my car has been taken appart and Cryoed as well as Rim polished the case has also been coated. I do not know how it will hold up but I plan to put about 1000 Hp to it
D.

I have put 400 WHP and 390 WTQ through my F40 with no problems yet.

Jack

------------------
WARNING: Surgeon General said it's okay to smoke 3800s

Stop thinking about HP when thinking about the trans can handle. It's mostly irrelevant. What matters is your engine's torque curve, vs. the transmission's gearing, and what the trans can handle repeatedly, if you're going to race it.

If you're going to AutoX and want to avoid breaking the trans, first thing to do is avoid installing an LSD. Having an LSD is going to put more stress on the trans.

And take the gear ratios and your torque/power chart, and figure out what RPM you would shift into each gear from, in both directions. Calculate the RPM drop, and where the RPM will be after you shift. If you shift, and the engine is suddenly making peak torque, or near it, you are much more likely to break something.

A few people have autocrossed with an F40 before, and I don't think anyone on here has broken the trans doing it. But I am not sure how much torque they were making, and how they were shifting it there, either. Zac88GT ran one bolted to a Northstar in AutoX in his old 88 gt.

so i should make the decision after im finished with building my engine? even then i wont know the torque curve until i put it in my car, since i havent been able to find anyplace here that has an engine dyno.


as for an lsd, i wasnt going to install one. ive never really had any trouble with only one tire spinning.

Well you can look at dyno charts of similar engine builds. It's not like your 3800 is going to be wildly different from most other 3800s. And the numbers should be close enough to give you a good idea of where the torque and power are going to be made, and when you're going to want to shift.

The f40s are cheap to buy, expensive to install. As far as I know it's the first gear ratio that everyone complains about, and I doubt that you'll be spending much time in first while auto crossing. The upside is that after the expensive install, you can have an inexpensive spare sitting there ready for replacement. I bought two for just that reason.

Right. If you're going to drive on the AutoX course significantly more than the highway, the F40 is probably the wrong choice anyway. You'd want to find something with nice ratios in gears 1-3, since that's where most of the time will be spent, and good 4/5 OD gears for highway/town cruising. And you need to find something with a strong second gear that isn't going to blow out easily, but that's very hard to do in the GM FWD arena.

The F23 Getrag would probably be a better AutoX trans, but it's second gear is a bit weak, so it's really what you'd be risking blowing up. And the suggestions I gave previously will still apply to any trans you are thinking about using. Just make sure the internals are strong enough for what you need to do with it, and you should be good.