late part throttle shift 4L60E

[tayto]

should be throwing a code 38 if that's the case. FWIW, my 700r4 doesn't shift to 4th until 45 mph. in your datalog you should see if it's commanding shift solenoid A ON and B off @ 45mph (or whatever your shift table says), if it is and not shifting probably an internal problem with the trans.

[JD1964]

should be throwing a code 38 if that's the case. FWIW, my 700r4 doesn't shift to 4th until 45 mph. in your datalog you should see if it's commanding shift solenoid A ON and B off @ 45mph (or whatever your shift table says), if it is and not shifting probably an internal problem with the trans.

Thanks. I need to check the flags in the bin to see how they are set. The previous tuner turned some stuff off but I'm not sure exactly what was turned off or left on.

[JD1964]

Worked on it a little this evening. I fixed the brake switch and now it has the signal it needs to allow converter lockup which I verified on a test drive.

I have not changed anything in the bin yet but I hooked up EEhack and noticed a code logged. 21 - throttle position high - cleared the code.

Also in EEhack I observed the TPS % readings with KOEO. It went up normally as the pedal was pushed from 0 to 100 but at 100, there was still a little bit of pedal movement available towards the floor. I continued to push it down and when totally floored, the TPS percentage suddenly drops to 4.3 %. That can be good can it?

Earlier in the project I had been chasing suspected vacuum leaks and I was fiddling with the throttle stop screw and TSP adjustment (slotted mount holes). What do you bet I need to revisit that throttle stop and TPS position adjustement?

Since discovering the TPS percentage drops to 4.3 % at WOT, I test drove limiting the throttle opening to about 50%. It drove and shifted great.

[JD1964]

Btw, I understand that the brake pedal switch may only control unlocking of converter.

Speaking of lockup, under normal operation of the 1994 Z28 4L60e, does the converter only lock up in 4th, or does it also lock up in 2nd or 3rd?

Meanwhile, I’ll keep you posted when I get to sorting out the possible TPS issue. I’m fairly confident there’s not an internal transmission problem.

[LeMarky Dissod]

Speaking of lockup, under normal operation of the 1994 Z28 4L60E, does the converter only lock up in 4th, or does it also lock up in 2nd or 3rd?

Under normal operation of any LT1 coupe, hatch, sedan, or wagon, the TCC can lock in 3rd or 4th.
Although we COULD command it to lockup in 2nd, even if the correct 'TCC Lock' & 'TCC Unlock' values are used (and I personally do NOT believe in PWM of the TCC, I only use '94 values), locking it in 2nd is just not worth it under most circumstances. GM did not lock the TCC in 2nd.

Preaching to the choir, but … GM rushed to upshift to 4th ASAP to appease unrealistic CAFE MpG tests.
At boring TPS% & decidedly boring road speeds where MpGs are a major goal, 3rd&Locked is almost always better than 4th&Unlocked for the 4L60E - with <3.73 axle.
It may feel a bit odd until you calibrate the TCC Lock & Unlock road speeds to your foot & taste.

Once you've readjusted the physical throttle body properly, your TPS percentages - or are those Voltages? - should behave properly.

[JD1964]

Under normal operation of any LT1 coupe, hatch, sedan, or wagon, the TCC can lock in 3rd or 4th.

Once you've readjusted the physical throttle body properly, your TPS percentages - or are those Voltages? - should behave properly.

3rd or 4th, got it.

Those numbers I reported are throttle opening percentages. I plan to investigate the voltage values as well.

[tayto]

my current non-ecu controlled lockup is useless until about 100kph. Shifts into 4th and immediately locks up. I've been driving around in D until I swap in TBI harness and/or re-gear (currently 3.42s, want 4.11s or 4.56s). I will be keeping Qjet for now and have ECU control timing and lockup.