zader

I've been autocrossing my 2006 SLK350 for the last 5 years, it has an automatic trans that is painfully slow to engage when downshifting under heavy acceleration. I am considering the Renntech transmission upgrade but don't want to spend the money and have the same problem. Anyone have experience with this?

chglk

"Downshifting under heavy acceleration"?
That's a bit of an oxymoron isn't it?
I can see downshifting during de-celeration, and UPshifting during acceleration, but not downshifting under heavy acceleration. Sure that's what you mean?

zader

If you are cruising and you push the gas pedal to the floor to accelerate, the transmission will downshift to give you faster acceleration. My engine revs quickly but there is quite a pause before there is any forward acceleration.

chglk

Oh, so you mean auto downshift. If your's seems slow are you using the S or sport selection? This mode increases response of downshifts when WOT. The other option is to manually select gear, especially when auto crossing, which is the preferred method. A transmission mod seems a costly solution for a small improvement in performance, IMHO.

CDM Motorsports

We do allot of transmissions. So you are having a delay on downshifts. Is it on all gears?
You may have an issue, hard at this point to diagnose online. But i dont think you need a renntech trans to fix it.
How long have you had the car, have you serviced the trans? Is this a new problem. Have you had anyone reset the shift adapts?

zader

It has always been this way, since the car was new. Just not a great transmission I guess. I recently learned how to reset the adaptive shifting and that has helped with shifting in general. But it has not corrected this delay before the transmission engages when I floor it.