I have a 94 F-150 w/ a 302 (5.0L), 4x4, Automatic. The transmission was re-built and a new torque converter put in about 12,300 miles ago.

My truck has an issue with the rpm's going up (over 500 increase) intermittenly, with no change in speed. This would happen with me holding speed and on level ground. I usually drive in town so between 20-35mph. I took it in last week to the transmission shop that did the rebuild and torque converter. They said it sounded electrical, after a drive test and scan they told me it was the speed sensor that is located on the rear end and replaced it.

However later that day going up a hill after a stop it did NOT want to accelerate above 10-15 even while I was depressing the pedal, then all of a sudden it shifted violently and the speed increased. Tonight the truck was going up hill and again 10-15mph, when I tried to accelerate the rpms would go up (over 2500-which is high for my baby), but the truck did not speed up.

Ideas??

 

The other night I was driving and it had problems accelerating from stop lights. Tonight I decided to see if I could get any more clues by keeping it in the driveway. I turned my truck on and after it warmed up (and knocked down to it's normal idle of about 800rpm I decided to take it up slowly and let off the gas to mock a gentle acceleration. I did this to 1000, 1500 & 2000rpms. When I let off it went down, bouced up , down and settled.

Then I decided to pretend I was taking off from a stoplight. I took it up to 2000 and let go. The rpms went WAY down (to maybe 300) the truck wanted to die. I noticed that the amp meter also fell dramatically. I am leaning more and more towards electric. If she "acts up" like before you can manually shift her and she's fine. She had her tranny/torque converter done @ the best tranny shop by an experience professional. He has done well over 50 trannys.

 

This transmission has exactly one pressure test port. It's line pressure.

The intermittent 500 RPM slip is a common problem with this transmission. It is caused by a faulty Transmission Range Sensor (TRS.) The TRS, also called the Neutral Safety Switch, is located on the driver's side of the transmission.

When the TRS starts to fail it randomly tells the computer that you have moved the shifter from D to N. The computer then tells the trans to shift to neutral. Usually the fault only exists for a second or two, and then it reads D again and the computer tells the trans to shift back into gear.

If the trans shop got a code for a speed sensor and replaced the sensor, they need to understand that the code does not necessarily mean there is something wrong with the sensor itself. Quite often the problem is a damaged or corroded wire to the speed sensor.

 

The shop did tell me the code doesn't mean it's the speed sensor 100% and that if the problem occurred again (which it has) that it is something in the wiring. (ex: bad wire, TRS, or TCM).

Would a bad TRS also make the amps draw down when I let off the accelerator?

 

No, it would not.