robbie21mma

im looking to buy a new mustang gt07' or 08' the thing is i want to put a procharger or some other supercharger on it and full exhaust, heres the catch i dont want a standard shift i want a automatic so my question is how much power will the auto transmission hold? does anyone know about the auto transmission in the new mustang and how reliable it iswith a power adder?

Mikes_BLK_GT

You should upgrade the TC if you go with FI, maybe a transimission coolerand bigger pan as well. The 5r55s is weaker shifting into 3rd and 4th gear and is weaker than the older c-4's and 4r70w's partially due to it's being smaller. Alot depends on how much power you want to run, my impression is that once you get up closer to 450-500rwhp you are playing with fire on both your stock trans and motor.

Wally39

The guy that fixed my transmission told me to shift it myself when racing someone. He said there is more pressure and more bands etc are engaged. I figured I'd listen to him since he runs a very well known transmission shop.

Mikes_BLK_GT

I know that shifting into 3rd and 4th are synchronous shifts which means more moving parts which means more chance of breaking something. I have not heard of shifting manually to save the tranny but if you trust the guy I'm am quite sure he know's much more about tranny's than me. A transmission's biggest enemey is going ot be heat so if you can reduce friction/heat your better off. An upgraded aftermarket TC(PI has been recommended and is whoI would go with when the time comes)would go along ways in that department since they lockup better when needed vs a stock TC which spins more causing more potential for damage.

Heavyg72

Definitely go with a TC upgrade when going F/I and if possible go with a deep pan for the tranny as well. Brenspeed did my installation and tuning and he did mention the weakest link on the auto is the 3rd gear band. I had him back off the shift pressure a bit on 3rd to help some. I did both the TC and deep pan upgrades as well and after 4K since the installation I haven't had any issues. Good luck!

johnnyv8

I know ford will only warrnaty there 400hp whipple supercharger, not there 500hp one. and they dont even mark a 500 hp superkit for an auto gt, according to ford; it wont last.

so im "quessing" around 400rwhp mark.

22kart22

You should be fine for normal "fun".

If you plan on racing and beating the hell outa the thing, then really consider upgrading!

drbobvs

Yes, 3rd gear is the weak link in our trannys. Actually it would be better increase shift pressure not decrease it going into 3rd to reduce the band slip. I've seen a tranny lose third gear running 12psi whipple, however JDM is still running his completely stock auto tranny in his blue 10 sec Saleen, and he runs it often! So your guess is as good as mine as to a safe limit overall.

I too would suggest a T/C upgrade, but more importantly a tranny cooler, perhaps 2 of them, and changing to synthetic tranny fluid. Currently, Amsoil is the only available synthetic replacement for our auto trannys. A deep pan that holds 4 extra qts, currently there is only one offered and is about $400, is another option but as long as the fluid stays cool it doesn't matter if there is 12 qts or 16qts in there. I am having all the above upgrades, except the pan,done on Friday and hopefully will be clear to up the boost to 10psi after that.