My 2002 mountaineer, 2WD, 4.0, suddenly started downshifting or appearing to go into neutral by itself. A scan showed no signal from the rear speed sensor which i had replaced. Problem still exists. If I manually put it in 3rd instead of drive, no problem except i can only drive 40 MPH as RPM's gets too high. Does this sound like a transmission problem? I just had a factory remanufactured transmission put in about 8 months ago. I haven't had it rescanned yet but I'm wondering if "no signal" could mean it the problem was something like the wiring harness instead of the sensor itself? Appreciate any feedback.

 

No.. you do not have a transmission problem, it is controlled by the same PCM that controls the engine and speed input is a critical parameter for trans control. So it is likely you have a problem with that signal elsewhere besiides the VSS sensor, it could be in the wiring harness but it could also be with the PSOM(Programmable Speedometer Odometer Module), have you noticed any issues with the speedo or ODO? Blinking display? Bouncing needle?

 

Conanski, Thanks for the reply. I have had no issues with speedometer nor the OD light blinking. One thing i forgot to add was that it usually downshifts when i let off the gas...almost like someone shifted down 2 gears.

 

I'm new to site so I''m not sure of correct way to reply. There has been no blinking OD light, no problems with speedometer (that i have noticed). The ABS light has been on for over a year. Also, when i drive it in 3rd gear it works ok but i can hear a fairly loud whistle that corresponds with the RPMs. When i let off the gas the whistle stops.

 

The transmission control does take input from the brake system, so that has to be functioning correctly or the transmission may not shift properly. At the very least, the transmission probably was not engaging the torque converter lockup during the whole time that the ABS light was on.

I would find out what's causing the ABS light. If there's a way to run a self test on it to get error codes, I would start there.