E4od delayed upshifting

He guys,
Im having an issue with my 91 f350 e4od transmission that for the past couple days has been not up shifting as it usually would, its holding gears until about 2500 pm I can sometimes get it to shift sooner if play with the throttle a bit but still holds the gears for higher rpms than usual. I checked the fipl sensor its getting .96v at idle and about 4.6v at wot. I checked the rear diff sensor and seemed good but went ahead and replaced it anyway but didn't change anything with shifting. Im not sure if the transmission uses that sensor on the diff or the one on the transmission case for speed reference. I have not checked the vss thats on the transmission yet. Also I have the banks transcomnand tcm and it shifts just fine and goes trhough all the gears it just takes too long to shift. I cant tell if the tc is locking up or not. Anyone have any pointers on what I should check or what this problem could be?

If it has a speedo cable with vss in it going into the trans or t case, the trans uses that one

Black dawg said:

If it has a speedo cable with vss in it going into the trans or t case, the trans uses that one

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Correct. Trucks up to 1991 still use the speedometer cable. 1992 and up combined the rear abs with a vehicle speed sensor, which also drives the electronic speedometer.

Thanks guys. Ill check the transmission mounted one. Do you happen to know what the test procedure and resistance/voltage reading should be?

david85 said:

Correct. Trucks up to 1991 still use the speedometer cable. 1992 and up combined the rear abs with a vehicle speed sensor, which also drives the electronic speedometer.

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Your FIPL/TPS is out of range technically. Throttle Position Sensor should read 1.2v at idle and anything over 4.0v at WOT should be good. The TPS is considered a "wear" item and I think 50k miles is its expected lifespan.
If you end up buying a new VSS I had trouble with the Dorman version in that the speedo cable would not insert far enough into the VSS for everything to be reassembled. I bought a different brand VSS and it worked no problem.

I recall reading about two replacement TPS parts to choose from - black or grey plastic with black TPS being a better quality. Anyone else?

Greenie said:

I recall reading about two replacement TPS parts to choose from - black or grey plastic with black TPS being a better quality. Anyone else?

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I think all TPS are black now since Motorcraft no longer produces them. Standard Motor Products TPS has been fine. I've compared a few NOS Motorcraft TPS to a new SMP version and they both performed the same--slightly different resistance values when testing them individually but as long as voltage range was 1.2v-4.X the shifting was proper. Just my own experience here but the idle voltage setting seems to be more important than the WOT voltage.

Dirt Leg I think) would be the one who's had a lot of bad experience a couple of years back. He'd be able to say what did and didn't work. He had one that only lasted for a few hundred miles.