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When i start the truck up and drive away it takes off just fine. After a few starts and stops through out town it almost seems like its not downshifting to first and is taking off in second. It revs high just to get itself moving. Get to my buddies shop, put in neutral and check fluid. Everything looks good. I turned the truck off for about 2 minutes and go to leave and it shifts just fine again. Anyone have a clue as to what might be the problem?
I'm going to take a guess here on the year of your truck. You are probably in the '96 to '98 range. If my guess is right, then chances are you are actually starting off in 3rd, not second. If my guess is right, then you are in what's called "limp mode" when this happens. The PCM is getting a signal from inside trans it does not like and is causing the 3rd gear starts. First step is to check for codes and go from there. If no codes you may need to check pressures in trans to make sure they are up to par.
Once you pull the code, most times it will come back as governer pressure sensor/solenoid voltage too high or low or something like that. At this point a check of pressures would be appropriate and then replace parts as needed. Pulling codes gives you a point to start checking. Another thing to do is to simply manually shift trans. If you can manually shift trans you basically eliminate any hydraulic problems. This is not 100% foolproof, therefore checking trans pressures is recommended. If pressures come back good, then it is time for replacing parts. If pressures don't come back good, then it could be time to start scheduling things. You need to know some history of trans, as an aftermarket performance trans or one with modified valve body can come back with some high pressure readings. Some performance trans will not shift perfect when dead cold. You are fighting the PCM factory settings, cold oil and an aftermarket high pressure trans. Put all three together and sometimes you'll get weird shifts when ice cold, normal shifting after a short drive to warm fluid.
Ill have to wait until next week to throw my buddies snap-on reader to it. the tranny was rebuilt with a high pressure valve body. the weird thing is though is that ill start it up when its been sitting all night. let it idle for a bit, hop in and drive away and it shifts great. takes off perfect, firm shifts, torque converter locks up every time in OD with no slipping. Its like after driving it for a bit then it starts to act up. only on starts though. real sluggish taking off. like you said, like its starting in third. ill shut the truck off and start it back up and drive away and all is fine again.
07 QCLB 5.9 - 6 inch Top Gun Customz, 35x12.5x18's
Yea i have same problem with my tranny but only after driving it for a constant highway speed then when i slow down it wont downshift pass third gear. I have to stop shut truck off then disconnect pcm for it to reset itself. Pain in the but because anytime i drive on the highway for more than 40 miles or so it goes in limp mode! When it does go into limp mode you can't manually shift it without resetting pcm. I'm not sure whats going on here
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