D
dirkmc3
Guest
Ok...official road test today on the 97 Land Rover Discovery after replacing the valve body assy due to a shifting problem..... and.....no difference in the transmission. The initial shifting problem is still there!!!!
The trans is a ZF4HP22 4sp manual (The valve body is not controlled by the ECU)automatic.
Here is the description of the problem...the trans will not upshift into 4th (hangs in 3rd)unless its cold. As it gets hot, it then begins to hang in 2nd. In both cases I can slide the gearbox into Neutral and pump the accelerator to build engine pressure and drop back into Drive to prompt the upshift, but as soon as I come to a neutral throttle position or let off the accellerator, it will immediately and somethimes abruptly downshift back into 3rd, or 2nd .
Questions...there is some type of a tourque converter or clutch pack lock up mechanism is there not??
Is there some type of TPS or electronic modulation of input to the transmission that could be malfunctioning when it gets hot?.
Or could the transmission oil pump be bad...(hence the revving to build pressure prompts the upshift) ?
Could Vaccum leaks or dirty lines may be causing a pressure problem?
So far.. fresh fluid and filter, new valve control block assy. >
Hell...I think I'll just get one from a breaker...Any transmission Mechanics out there with ideas
Thanks!!
__________________
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants".
...Thomas Jefferson.....
The trans is a ZF4HP22 4sp manual (The valve body is not controlled by the ECU)automatic.
Here is the description of the problem...the trans will not upshift into 4th (hangs in 3rd)unless its cold. As it gets hot, it then begins to hang in 2nd. In both cases I can slide the gearbox into Neutral and pump the accelerator to build engine pressure and drop back into Drive to prompt the upshift, but as soon as I come to a neutral throttle position or let off the accellerator, it will immediately and somethimes abruptly downshift back into 3rd, or 2nd .
Questions...there is some type of a tourque converter or clutch pack lock up mechanism is there not??
Is there some type of TPS or electronic modulation of input to the transmission that could be malfunctioning when it gets hot?.
Or could the transmission oil pump be bad...(hence the revving to build pressure prompts the upshift) ?
Could Vaccum leaks or dirty lines may be causing a pressure problem?
So far.. fresh fluid and filter, new valve control block assy. >
Hell...I think I'll just get one from a breaker...Any transmission Mechanics out there with ideas
Thanks!!
__________________
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants".
...Thomas Jefferson.....
