Lawdog734
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- Location
- Colbert, GA
My 4L80 in my non-turbo 6.5 is giving me fits in trying to get things to operate normally - I was hoping you guys might be able to assist with a couple of questions.
A little background on what's going on.
The truck seems to operate/shift fine. When I drive it around a bit, it shifts alright - not awesome but I can deal with it. It seems to want to drag out first and second a little long, but it's probably just the way the transmission is geared I'd guess. Eventually the transmission almost "misses" for no real apparent reason and then the transmission light will start to flash in no particular pattern. I might drive it for 30-40 minutes and it happens, or it could be 5, but it always happens.
So this is what I've checked so far:
- when putting the tcm in diagnostic mode, all it does is flash 12, over and over. It gives no codes. I've driven it around and stopped the truck when it started flashing - again, no codes other than 12.
- I've replaced the tcm with another known good unit and it's worked fine
- I've ohm'd out all the connections in the J1 plug and they're all within spec. I assume this means there's likely no problem with the transmission itself?
- I have also followed the instructions from an older post here from General Bilstein on checking the throttle position sensor. He had suggested that most trucks, when you ohm the "s" and "p" pins, should show between 1850-1950 ohms. When I checked mine, it was at 1340 ohms. Adjusting the tps clockwise (towards the front) to max travel only increased it to 1460 ohms. At max travel ccw, it registered in the 650'ish range. As expected, when driving with the tps at max position clockwise, the shifts were there, but very, very soft. I have not diagnosed it any further for voltage. I've got a test gauge block, but forgot to pick up the jumper, which will be here this week.
My question is - do you think this sounds more mechanical, or electrical? The transmission does shift. What do you think about the TPS, if I can't adjust it so it's between 1850-1950 ohms, is it shot? Do they wear out?
Thoughts or suggestions?
A little background on what's going on.
The truck seems to operate/shift fine. When I drive it around a bit, it shifts alright - not awesome but I can deal with it. It seems to want to drag out first and second a little long, but it's probably just the way the transmission is geared I'd guess. Eventually the transmission almost "misses" for no real apparent reason and then the transmission light will start to flash in no particular pattern. I might drive it for 30-40 minutes and it happens, or it could be 5, but it always happens.
So this is what I've checked so far:
- when putting the tcm in diagnostic mode, all it does is flash 12, over and over. It gives no codes. I've driven it around and stopped the truck when it started flashing - again, no codes other than 12.
- I've replaced the tcm with another known good unit and it's worked fine
- I've ohm'd out all the connections in the J1 plug and they're all within spec. I assume this means there's likely no problem with the transmission itself?
- I have also followed the instructions from an older post here from General Bilstein on checking the throttle position sensor. He had suggested that most trucks, when you ohm the "s" and "p" pins, should show between 1850-1950 ohms. When I checked mine, it was at 1340 ohms. Adjusting the tps clockwise (towards the front) to max travel only increased it to 1460 ohms. At max travel ccw, it registered in the 650'ish range. As expected, when driving with the tps at max position clockwise, the shifts were there, but very, very soft. I have not diagnosed it any further for voltage. I've got a test gauge block, but forgot to pick up the jumper, which will be here this week.
My question is - do you think this sounds more mechanical, or electrical? The transmission does shift. What do you think about the TPS, if I can't adjust it so it's between 1850-1950 ohms, is it shot? Do they wear out?
Thoughts or suggestions?