LS swap transmission shift points

[DaveB]

The LS swap in my Scrambler has been running well but the transmission shift points seem a bit off. I've been reading up on how they control the shift points and found that the main controls used for the shifts are the TPS output and the vehicle speed. I realized that I never told the tuner that my gear ratio and tire size are not matching the stock ratio and tire size. The 2001 Yukon I got the engine out of had 3.73 gears and 30.6" tires (metric conversion value). My Jeep has 33" tires and 4.56 gears. Doing the math my effective ratio is 13.4% off from stock. The ECM is thinking that I am going faster than I really am and shifting up sooner than a stock setup. Shifting down should be later than stock. Have those of you who have done the LS swap adjusted your tranny shift points to compensate for tires and gears ? A lot of the tuning articles I read said it's based a lot on how you like it which is very subjective.

 

[Greg]

Your best option is going to be finding someone that has HP Tuners and they can adjust the tire size and gear ratio for you, in the ECU. It's pretty easy to do.

If they're really knowledgeable, they can raise or lower the shift points to where as you prefer, once the gear ratio and tire size is set. That might require plugging the laptop into the ECU and doing some test drives, making changes along the way and see what you like. That is more involved and takes time.

 

[UNSTUCK]

Just what Greg said. I'm really surprised your tuner did not ask you those two VERY important questions. My tuner has ridden along with me in the past and made shift point and firmness adjustments based on throttle position.

 

[DaveB]

I'll have to get back with him