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1994 F150 Harsh shifts - PSOM to blame?

O'Rattlecan

Redneck Prognosticator
26,689
797
Belton, MO
Hey guys,

If you read my posts (God bless your patience) then you might already know I've been fighting a harsh shifting transmission for about 5 years. The transmission even was freshly rebuilt and it's still out of control. I've thrown speed sensors (VSS), throttle position sensors, fluid changes, solenoid packs... No matter what I do, it persists.

There is a component that I didn't know existed. It's called the PSOM, which is short for Programmable Speedometer & Odometer Module. I knew the transmission used the speed sensor to determine the strength of shifts. However, I didn't know it routed through this PSOM module.

I haven't ever touched this PSOM module. Most guys with a bad PSOM complain of a speedometer not working, harsh shifts, and sometimes even the odometer is blank. The only symptom I have is the harsh shifts.

Anyway.... Has anyone dealt with this issue? Vince, have you repaired these boards or replaced them completely? I can't find them for sale, so I'm thinking I will have to have it rebuilt or get something from a salvage yard.

Ryan
 

O'Rattlecan

Redneck Prognosticator
26,689
797
Belton, MO
Update for the curious!

The harsh shifts were caused by a bad connection with high resistance in the wire harness that connects to the E4OD on the passenger side of the transmission. Over the years, the road salt and heat from the nearby exhaust deteriorated the wires and their insulation.

Problem solved, it shifts smooth as butter now.

Ryan
 

Lost

PA Chapter leader
3,288
33
central PA
I'll have to try this . My truck 15000 on trans will shift harsh . shut it off fine. Next time might act like in neutral under light acceleration .

Another wont shift out of 1 ,or 2nd gear once in while then fine for months .

Trans shop no help .
 
I'll have to try this . My truck 15000 on trans will shift harsh . shut it off fine. Next time might act like in neutral under light acceleration .

Another wont shift out of 1 ,or 2nd gear once in while then fine for months .

Trans shop no help .
Hi there, my truck is doing the exact same thing. Ever figure out what was causing it?
 
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