E9X 6AT Trans slipping during launch at the Drag Strip

[Silent11]

Hey guys

i have a 07 335i with a 6At trans, xhp stage 3

e50 tune, around 450 whp 550 torque

Mt ET Street SS Drag radials

I launch in 2nd and as soon as the car hooks it slips into third

if i add air to the tires , over 20 psi, it spins but stays in 2nd

Same thing on street tires, spins but stays in 2nd

i lowered the boost to 19psi from 21.5 in 2nd and it slips again and goes into third

What are my options ?

 

[chrisdfv]

What are my options ?

• Lower torque.
• If you want to consider saving your transmission. Service it. Do a zip kit to the valve body(cheap and easy to DIY).
• To further improve your 6AT on top of the mentioned items above, change the clutches and bushings to PD items.
• Manual swap.

 

[Cheezy]

Launch in 1st. Only be on the converter for less than 4 seconds. I usually pre stage, then always stage last so I can get on the converter just long enough for the lights to drop. Anything much longer it does what you're describing.

 

[Silent11]

i never spend more than 2 sec on the converter, i even tried easing into it and once it hooked at 4000 rpm it did it again, not sure about 1st gear launch, with all this torque im thinking the axles wont last long.

 

[typedRew]

When was the last trans service?

Fluid and filter and see if it changes anything. Might even have to do that a couple times to really freshen it up.

Mine has done this when I tried a 2nd gear launch with my xdrive. Basically just feels like the torque converter is spinning and not sending anything to the wheels. Like i'm asking too much of it. Of course my trans also desperately needs serviced. I plan on doing 3 or 4 over the course of a few months to try and get mostly new fluid in it without shocking the system.

 

[Silent11]

i contacted xhp and they said fluid change wont help ( ive never done it, car has 120.000 miles ) they recommended changing the clutches which is my last resort

 

[typedRew]

i contacted xhp and they said fluid change wont help ( ive never done it, car has 120.000 miles ) they recommended changing the clutches which is my last resort

well shit