Re: Jeep Grand Cherokee 2001
So we are talking about the 5-45RFE transmission. Did the problem of putting in Drive and not moving happen after the fluid change?
The check engine light is not on? Just to be sure that there are no fault codes set, do the following: switch the ignition switch OFF/ON three times and leave it in ON at the third time. The odometer will show DONE when all ok, or a fault code, which could help in the trouble shooting.
There where cases where at first startup it took several seconds for the jeep to start moving. That had to do with a faulty checkvalve inside the round spin-on filter inside the transmission. The fluid from the torque converter could drain back to the sump and it would take some seconds after start-up to fill the torque converter. But you also have a problem when coming to a stop, so this seems to be a different problem.
New fluid has strong cleaning action and could remove particles from one position and take them to small orifices, where it can block (partly) the orifice.
Since you say that in reverse all works ok, my suspision is going to the solenoid assy or the electrical connector on top of it (reverse is using the manual valve in the valve body). Maybe you could start cleaning the big connector from this solenoid block, its positioned on the left side of the transmission, its a big square connector with many wires. There is a locking bar on it which you have to move up, so that it will push the connector upwards.
TPS and speed sensors are a possibility as well, but they generally cause shifting problems in all gears.
Another possibility is a sticking solenoid switch valve inside the valve body, but it will switch the check engine light on.