I have replaced the motor and the transmission and will not go into gear unless the rpms’ are high. The reason for replacing the transmission was that it would go into reverse but no forward gears. not sure what is going on or how to fix it. Any help would be greatful.
Have you checked the fluid level correctly??
Did you flush the cooler and cooler lines with trans flush??
Did you replace the trans with a used trans or reman or have it rebuilt by a shop??
Also try putting the transmission in neutral (before any drive gear) for a few seconds to see if that helps as the converter has drain-back complaints that are associated with wear in the pressure regulator valve and TCC regulator valve bores. Older TorqueFlite transmissions didn’t fill the converter in park and would drain back over hours not in use, so starting them in neutral or putting into neutral before D/R would fill the converter and you would be good to go… I have been using the TransGo kits for 30+ years now to solve that issue… They have a Kit for your 42RLE also…
Not saying that is your issue, but worth trying…
Suggest to provide some more info, like why did you replace both the engine and transmission, when the symptom was the transmission wouldn’t go into forward gears? That doesn’t seem like an engine problem. What’s the engine/transmission configuration, before and after? Is the replacement transmission a used unit from a junkyard wreck? Or a professionally rebuilt unit? Since your car is equpped w/ OBD II presumably, do you have any engine or transmission diagnostic codes in computer memory.
I’ll venture a guess anyway. Automatic transmissions work by pumping the transmission fluid to a very high pressure, then using the force of that pressure, routed through a bevy of valves, some spring loaded passive, some electric solenoid activated, to the correct place so it pushes on something to effect the gear change. When the gear change doesn’t occur, the problem is likely from among these possibilities
- Transmission isn’t being commanded properly to change gears. Usually some combo of mechanical or electrical problem.
- Fluid pressure is too low. Low fluid level, defective pump, leaking valves or valve body. When you increase the engine rpm, that may be increasing the pump rpm, and boosting the pressure enough temporarily. Sometimes you can get lucky and re-torquing the valve body bolts will restore enough fluid pressure.
- Internal planetary gear, band, and clutch problems. Usually caused by low fluid, transmission overheating, or just normal wear w/miles driven.
Auto trans are such complicated gadgets, probably best to take your car to a pro mechanic with expertise on that transmission and get a professional assessment. Then you can decide based on what they say whether you want to tackle the repairs on your own, hire them out, or a combo.