4L60E issue. Torque converter problem or transmission problem
 

So I'm driving down the road with the transmission lever on D cruising around 50 mph and the TCC is locked. I shift the lever to OD at speeds over 60 mph for better highway fuel economy. So I apply about 30% throttle to pass a slow moving car. On both 3rd and 4th gear, the TCC seems to be slipping even if locked. Sounds like someone with a manual transmission when their clutch is slipping badly. On HPtuners, I have disabled pulsewidth modulation for a solid TCC lock up function and when more throttle is applied when the TCC is commanded, it is the same effect like a manual car with a slipping clutch when more throttle is given. It stops slipping when I lessen the throttle. The torque converter is a new 3800 stall Vigilante 9.5" converter. So is the problem with the 3-4 clutchpacks in my 4L60E transmission or is it the lock up clutch of the torque converter itself? I know the stock 12" TCC did not slip when lock up was commanded with more throttle to pass. Am I right?

If you have a solid WOT 2-3 shift then it's not the 3-4 clutches, it's the tuning.

Yeah, 2-3 shifts are firm as well as the 3-4 shifts, from part throttle to WOT. No "soft slippy shifts," no rev limiter banging then shifts. FIRM!

Are you saying that a bad tune can cause the TCC to slip? I don't get it. When the TCC is commanded, it would be at the 100% duty cycle lock because I tuned out the pulse width modulation feature on HPtuners to further reduce wear and tear on the TCC lock up plate in the torque converter.

In addition to this problem, TCC lock up seems to slip even more when I've been driving stop-and-go for more than 30 minutes in hot weather. Other than that, the slip is less pronounced, but still very noticeable when the motor and transmission are just warming up and at the minimum temperature for the ECM to command TCC lock up.

Well in the above post you are asking if it could be the 3-4 clutch or tcc clutch. I just suggested that if it has a good 2-3 and 3-4 then you can rule out the 3-4 clutch as being bad.

So that leaves the tcc or tuning.

Ok then so your tcc slip is a low pitch grind/rumble right?

It sounds to me like your tcc is simply unlocking because you didn't mention a horrible rumble (tcc slip). If you're logging tcc pwm you're going to see a pwm number even when the tcc is not locked.

A simple solution to answer the question is it tuning or mechanical. Go into hptuners VCM controls, lock the converter manually and see if it slips under load. If it doesn't slip under load while manually locked then it's the apply and release speeds.

If PCM detects misfires it will unlock the TCC.. so scan/log for misfires.

There is no TCC shudder or grinding noise when the lockup is applied 100%. It just slips when locked when there is 20%-40% throttle to pass someone. You can feel it unlock completely once you get over half throttle.

Bumping an old thread my 98 is doing the same thing even at low throttle at 70mph or more it feels like its slipping. Gas mileage has went from 22 to 17 in just a couple tanks. At 80mph cruising it surges like its slipping. Car has a 3400 revmax converter with upgraded tcc.