1994 Ford E-Series Van Slipping of transmision at 45 to 55

DWMCDOUGALL

MEMBER
1994 FORD E-SERIES VAN
V8
2WD
AUTOMATIC
75,000 MILES

E350- 460 engine with heavy duty auto trans. W'o'drive in Chinook motorhome. After driving about 150 miles, the engine slowly rev's up while the speed slows down with transmission softly disengaging. Release of pressure on accelerator for a few seconds will result in a correction of the problem. This typically happens about 1 to 3 times on a 300 mile trip.
Took to Ford dealer 8-25-06, no problems found on eec check. Took to dealer again 10-27-07 and no problems found. Updated to newer version TR Sensor and VSS sensor.
Took back to dealer as new sensor made no difference. They checked hyd pressures and found ok. Rec. Try new transmission. Put in Remfg. Transmission, cooler, and rear speed sensor. Problem is still occurring! What is wrong?

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

This can be real tough to diagnose, as you have found out, but IF tranny is the correct E4OD and line pressures are good, it could be nothing to do with the tranny, a faulty TPS(Throttle possition sensor) that is a bit out of range, can cause shift problems and NOT set a code in the PCM.
Throttle Position Sensor (TPS) The TPS is a potentiometer mounted to the engine throttle body on gasoline engines and fuel injection pump on diesel engines. The PCM receives a signal from the TPS relaying throttle plate position (gas engines) or fuel delivery (diesel engines). TPS failure will cause PCM to operate in fail safe mode and raise line pressure to prevent transmission damage. This condition will result in harsh engagements, firm shift feel, abnormal shift schedule and TCC not engaging or cycling.