Are there programming tables in the 99 GMT-400 black box model PCM's that allow the PWM TCC to be set to 100% lockup on command and eliminate the converter pwm.

At 50-60 mph in OD it tries to lock the converter and then it slips from 50-125 is rpm on the tcc slip speed pid and it developes what I would call a shudder and noticeable vibration that is in perfect unison with the slip speed increasing. It does it hot or cold instantly. If you command the tcc to 100% lock via scanner while driving and during its acting up the problem goes away. Checked grounds checked power checked the trans fluid all the connectors are clean and tight.


This is on my personal 99 350 suburban. The stock transmission blew up and I installed a new SRTA GM trans in the truck and new GM computer at the same time to CYA. I noticed this problem right before the old trans failed a few weeks but attributed it to the trans failing it died at 160K stone stock. It seems the replacement trans is doing it as well so I'm hung on a trans problem or something I'm missing. I've done all the GM tests and the findings are inconclusive at best.

 

I don't see this table in HP Tuners but in Tunercat OBD2 there is this table. This table is from a 99 Suburban 5.7 file.

 

Dang that table is not in HP. All tests point at a faulty torque converter gm is sending another transmission to replace the complete unit. Hopefully that gets it. I thought about doing a transgo in it and deleting the pwm but it's brand stinkin new unit so it's got a problem and that would just mask it.

 

New tranny fixed it that was our first defective SRTA in over 30 years. Who woulda thunk it.

 

Wow, That is rare.