midwestdave33

Forgive me if this has bee asked before. I searched and couldn't find an applicable thread.

I'm looking to buy a set of MT ET drag radials to run at the track. My street tires are 32'' tall and the truck/trans is programed for that size.

The best drag radial that will fit on my extra set of existing 20'' wheels are 28.7'' in diameter.

Question is: Is the trans programed to shift at a given rpm or mph in my 6sp automatic trans?
Will the shorter slick affect the trans programming at the drag strip?

I'm aware this will lower my overall effective gear ratio and my speedometer will not be accurate but I just want to make sure the truck will shift right and not mess everything up.

Thanks in advance everyone!
dave

FFDP

iTrader: (2)

Yes, it will mess with the shifting.

The transmission uses both vehicle speed and rpm so the smaller tire will for sure mess with the shift points if not tuned for.

ZO6Ted

Agreed. I recall changing both in HP to get the desired shift point.