How much horsepower will a stock tranny take until it start's putting to much stress on it.

 

is it an automatic or 5 speed

 

Assuming it's an auto...

Tuning and driving style will be the biggest factors. A good tuner will make that tranny last a lot longer. 500+rwhp has been done numerous times on stock trannies with no issues. I believe there were a few closer to 600rwhp on stock trannies, but if you're racing it wont last long there.

 

It is an automatic and I am looking at buying an SCT tuner will that be a good tuner to help my transmission out

 

Yes, provided you get the custom tunes. Those are what really make it shine.

 

like mud said and i found out by askin some guys at the drag strip when i went a few days ago...i talked to 3 guys in 04-07 6.0L and they where runnin stock trans at 500rwhp (it was their first or second pass down the track in the life of the truck)...but honestly if you can spare the money to upgrade/rebuild the trans it is ALWAYS a good idea...ya its expensive but if you do a good high level rebuild you wont have to worry about you trans nearly as much...

so in short...ur good to 500+ (if you baby it) but i would try to rebuild the trans ASAP just to prevent any potential problems

 

it will last a little while. i made probably 20 passes at about 575rwhp and then i sprayed on top of it for about half of those. then i was runnin 632 on fuel and made 3 passes spraying on top of that. it went into limp mode on the third pass. it was slipping bad. my trap speed was showing it. in all i think it did pretty good .

 

I meant 500rwhp BEATING on it, not babying it. How many guys do you know running over 500rwhp that baby their trucks anyways?