I have a 1999 s10 blazer with what I am finding out to have a 2000 or newer 4.3 engine and a 1997 4l60e. I have a 2 inch lift and 31" tires on it and have been having some issues with the transmission. After placing the 31x9.50 tires on the rear temporarily for the winter a year ago I noticed that on any kind of up hill grade my TCC kicked out almost immediately. After making it over even a small hill if it didn't have a long enough stretch of down hill to speed it up it refused to kick back into lockup on level ground unless I increased my speed and let it slow down. On larger hills on express ways it will sometimes go strait out of lockup and into 3rd gear with little notice. I have since put on the 2" lift kit and have 31x10.50 tires on it and the problem has not gotten any better nor worse. I notice that when it occurs up hill my vacuum gauge nearly hits 0 and at the point just before it kicks out of lockup or drops into 3rd I loose roughly 3 mph from where my cruise was set at. Its almost as if it doesn't have enough power to climb a hill, or the transmission isn't transferring the power to the wheels right. I have replaced many parts in trying to find the cause of my tcc kicking out prematurly and I am stumped at this point. I have new fuel injectors (upgraded from the poppet style injectors to the new style), fuel pump, Head gaskets (leaking coolant into the exhaust), O2 sensors, installed a cam and lifters, tps, cts, most all the solenoids in the transmission except the pressure control solenoid, 4th gear servo (over sized upgrade), installed shift kit, transmission boost valve, and pwm tcc eliminator. Some parts were replaced for other reasons along with thinking it may help with my tcc problem. I have also had the computer flashed as well. One of my next things I am thinking about is posibly the torque converter itself. The stock stall speed is suppose to be at about 1600 rpms if I am correct, but mine is sitting at about 2200 rpms when I try and stall it I guess you could say. I'm just stumped at this point and I can't find anything about this kind of problem. If anyone has any good ideas of what it could even be please let me know. Thanks.

 

what speeds are you traveling when this happens?

 

It seems to happen anywhere from 50 and up from there. It seems that when its between 50 and 60 it is more sensitive to kicking out of lock up on even the smallest hills on a country back road. When I'm on the interstate at about 70 it tends to be less sensitive, but if I got up a slope and it levels out with no down slope the transmission refuses to kick back into lock up no matter what speed I have it set at unless I hit the gas to speed up then slow back down.

 

tcc lockup will only happen over 55mph...

 

The larger tires might have something to do with it. Did you have the PCM reflashed since you changed tire size? The PCM uses throttle position, engine rpm, MAP sensor, calculated engine load and vehicle speed to determine when to lock and unlock the converter. Maintaining a steady 35-40mph on the flat, the torque converter should lock up.

 

Mine usually locks up on level ground as low as 45 mph most of the time. I did have the pcm flashed after I had the bigger tires put on. I forgot to mention that I do have a programmer on my truck and had the tire size changed through the programmer. After I changed the tire size it did help it a little but no major change in how it acts. Would it make any difference though if I had the tire size changed by a programmer or if I actually flashed the pcm with the new tire size. According to my scanner I have it kicks out of lock up when I loose 3mph but I'm at 28% load or less.

 

Best to have the PCM flashed. The PCM, BCM, TCCM and EBCM all communicate with each other using class II serial data, and they share all of the data. I doubt that the programmer "plays nice" with them.

 

That kinda makes senses because the programmer also can adjust shift pressures and timing and when I fooled around with the shift timing it make the kick downs a lot worse. I will have to see about getting it flashed for the size I got on it and go from there.

 

Update: I took my blazer in to get the tire size actually flashed into the computer. I found they actually had to go through the ebcm and not the pcm. After the program it does take off better and shift more of when it should. It still kicks out of tcc in the same way though. The thing that bothers me is after it kicks out it refuses to kick back in on any level ground unless I gain speed off a down hill slope.