So I decided to spend plenty of money on a 408 but went cheap on my 4L60e tranny and just rebuilt it and supposedly upggraded internals. Well it didn't even last me 3 months. And that's cuz I haven't even taken it to the track just street use(on drag setup)breaking it in. Can someone recommend me a strong tranny to go with for my 408 that's pushing over 500 hp N/A? I will be spraying as well so maybe 700 hp would be the number on spray for the tranny to handle! Already have the suspension and S60 rearend.

 

just go to a 4l80 and forget about it, there are plenty of well built 60s around but they still have there limitations.

 

You might consider FLT's Level 7 with billet input and output shafts:

http://www.finishlinetrans.com/trans...rmance4L65.htm

It is a whopping $3895, but billet input/output shaft contribute $1000 to the price and I've been told are highly recommended with Nitrous.

I'm thrilled to see that FLT is now using the new Sonnax "Smart Tech" input drum which both increases the size of the 3-4 clutch and significantly strengthens it. I discussed it in this thread:

https://ls1tech.com/forums/automatic...-4-clutch.html

BTW - FLT also uses the billet overrun piston (and steel forward piston) I show in that thread.

I know that other builders are successfully testing that input drum in 700HP (heavy) trucks. You should of course ask FLT if that trans would handle your needs, but I suspect it will and they will give you a good warranty.

Obviously a good 4L80E would be sturdier yet, but by the time you buy a 4L80E and/or get it rebuilt, get a converter, get a crossmember, mod your tunnel, mod your harness, mod your PCM and take care of other details, that is also a costly upgrade.

 

I killed my flt lvl 7 with a 150 shot on a cam only car

 

Do you know what broke?
I recall that just last year the billet input/output shafts were an option on the Level 7 and they were not yet using the latest Sonnax input drum and sun shell.
In particular did you have a billet output shaft? I've been told that stock shafts often break with nitrous due to the sudden impact.

I'm not trying to promote FLT; I just want to have a better idea of when to steer people away from a 4L60E and toward a 4L80E.

 

Been thinking about a 4l80 but don't know what else would be needed for this swap. Any vendor/sponsor have a good deal going on for one of these 4l80's?

 

Speartech has the adapter harness, the swap isis very simple. There's a few companies that make the crossmember, and its fairly easy to tune. You would not need to do much to the transmission to handle that power level either