buddy
Active Member
Anyone have any experience as to why you would want to unlock the TCC when upshifting? GM programmed it to do this on the 4L80E, as well as downshift which makes sense to me to get some RPMs up. I have been testing it without unlocking in upshift and seems to firm up the shifting from 3rd to 4th, but I was wondering if anyone saw some downside to keeping it locked? Others also defeat the programming and install a switch to keep the TCC locked all the time when towing in 3rd or 4th, so it would be there for downshift too.
Is there some downside to keeping TCC locked in upshift?
The older mechanical auto tranny TCCs that locked from RPM obviously wouldnt unlock to upshift. It also seems that unlocking and relocking could contribute to slipping in the shift. Its going to lock up again immediately after it shifts.
When I compared the 4L60E programming to 4L80E programming I also noticed the lighter duty tranny would not unlock when slipping, like near its stall speed, which for the 4L80E 6.5 is about 1600rpm. I notice that my TCC wont lock up around 1500rpm for this reason, and the program keeps saying because of slipping. And in the code I have found that it is set this way. I can unset that, but something tells me slipping and lugging like that would not be good anyway. This contributes to why the 6.5 with 4L80E will be more efficient around 1800rpm than at 1500rpm cruising.
In the same kind of area, I also found where the code decided to unlock on low or zero TPS as well, and stopping it from doing that works really well for going downhill, stabbing the brake a good amount will unlock it if you want to coast. This is from OBD1 6.5TD programming.
Thanks for any input,
Tom
Is there some downside to keeping TCC locked in upshift?
The older mechanical auto tranny TCCs that locked from RPM obviously wouldnt unlock to upshift. It also seems that unlocking and relocking could contribute to slipping in the shift. Its going to lock up again immediately after it shifts.
When I compared the 4L60E programming to 4L80E programming I also noticed the lighter duty tranny would not unlock when slipping, like near its stall speed, which for the 4L80E 6.5 is about 1600rpm. I notice that my TCC wont lock up around 1500rpm for this reason, and the program keeps saying because of slipping. And in the code I have found that it is set this way. I can unset that, but something tells me slipping and lugging like that would not be good anyway. This contributes to why the 6.5 with 4L80E will be more efficient around 1800rpm than at 1500rpm cruising.
In the same kind of area, I also found where the code decided to unlock on low or zero TPS as well, and stopping it from doing that works really well for going downhill, stabbing the brake a good amount will unlock it if you want to coast. This is from OBD1 6.5TD programming.
Thanks for any input,
Tom