I have a transgo shift kit installed in the tranny and a 3000 stall and the shop tuned to ecu to allow the tranny to shift at 6,400 rpms. For a while the car was shifting at that point at WOT. But recently the car is shifting before this point. Yesterday it shifter at 5,500 and today it shifted at 4,500 from first to second gear. I couldn’t tell you about second to third though (to many cops in the area) If I manually shift I can reach these rpms just fine. What do you guys think? Tuning issue tranny issue?

 

Shift timing in the 80e is strictly a function of the PCM It can only do what its told nothing more, So something must be changing in your tuning to cause this to happen .Bad sensor ETC

 

i know i have a bad o2 sensor but that cant be the issue. What sensors should I be looking at. I haven’t made any tuning changes since the actual tune. I made some changes to the car recently. I installed a ported intake manifold, 58 mm T/B and a CAI. Those changes should be irrelevant to the problem though.

Thanks for your help

 

Actually that would not be correct, The PCM uses many many interrelated sensor readings to determine how the trans performs. Its a common mistake to assume that only trans setting affect trans performance, I hear it all the time. The likely culprit is the larger throttle body and TPS calibration, There a place in the tuning that need to be changed concerning the min and max TPS range it should be reset to MIN 0% and MAX 100%. oddly what happens is the PCM looks at MAF figures for load then looks at the throttle angle and sees an unexpected variance. So it reacts and changes the shift timing and pressure accordingly. Trans shift timing and pressures are affect by.
MAF READINGS,TPS READINGS,MAP READINGS,ENGINE RPM, ENGINE TEMP,TRANS TEMP, SPEED any mod that changes any one of these can change the way the PCM tells the trans what to do , This is true of the 4l60e and 4l80e and really any electronically controlled trans.
I hear from guys regulary having shift issues after CAM,INTAKE,TB, INTAKE and HEAD changes of complaints of quick shifting at WOT.

 

It makes alot of sence that the tps would need to be re adjusted after the tb install. The tranny would shift earlier if it dident know it was at WOT. So this is some info I need to give the tuner to allow him to make the adjustment or am i going to have to slot the tps?

 

He should know how to do it in tuning