HalfTon6.5
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Hey guys. I'm hoping a transmission guru can give me some good advice as to how best to proceed with an issue I'm having with a 4l80e.
'96 GMC 1500 6.5TD/4l80e with ~240,000 miles is shifting hard at all loads. Only DTCs I've pulled are EGR related (I've known for a while that the EGR solenoids failed), and I assume that even with a relatively cheap code reader I should see something referring to enhanced DTCs if they were present. I've verified resistance of trans control solenoids, and checked pressures to be:
Park, neutral, and forward gears - ~170 PSI
Reverse - ~270 PSI
These are at rest with foot on brake. Haven't stall tested or road tested. My understanding is that 171 PSI is max line pressure for park, neutral, and forward gears. If this is the case, can I assume a mechanical cause with the lack of DTCs? Could the PCM be commanding the high line pressure even without DTCs? Anyone familiar with the 4l80e have an educated guess? I'm tempted to try a new pressure control solenoid, but I really hate being a parts changer. Wondering if there's any other tests I could perform before I throw parts at it.
Any advice is much appreciated!
'96 GMC 1500 6.5TD/4l80e with ~240,000 miles is shifting hard at all loads. Only DTCs I've pulled are EGR related (I've known for a while that the EGR solenoids failed), and I assume that even with a relatively cheap code reader I should see something referring to enhanced DTCs if they were present. I've verified resistance of trans control solenoids, and checked pressures to be:
Park, neutral, and forward gears - ~170 PSI
Reverse - ~270 PSI
These are at rest with foot on brake. Haven't stall tested or road tested. My understanding is that 171 PSI is max line pressure for park, neutral, and forward gears. If this is the case, can I assume a mechanical cause with the lack of DTCs? Could the PCM be commanding the high line pressure even without DTCs? Anyone familiar with the 4l80e have an educated guess? I'm tempted to try a new pressure control solenoid, but I really hate being a parts changer. Wondering if there's any other tests I could perform before I throw parts at it.
Any advice is much appreciated!