1992 F250 E40D Tranny problems

[stump puller]

I know there's some Tranny wizards out there, I'm new here and this is my first post, well here goes, This is a computer assisted tranny E40D, and it seems to want to shift down all the time between 35 an 50 mph, it's a diesel with 132,000 miles, the fluid was just changed 6 months ago, you can be driving at a constant speed and the tach just climbs around 500 rpm and then just upshifts again, the fluid level is right on the cross lines, someone told me the filter should be changed or the selinoid is sticking, what do you think? Is it time to rebuild or replace or could it be one of those dang sensors,etc.

[ModMech]

You should have an electric switch on the injection pump that tells the transmission control module when to downshift, or upshift later due to hard acceleration. If this switch gets out of adjustment, it can cause symptoms you describe. My service manuals are at work, I will review them an post back tuesday.

[stump puller]

Thanks Mod Mech, where is this injection pump? and is this something I can adjust? I've only owned this truck and is my first diesel for less than a year, changing tranny filter today, will watch for your reply.

[97chevyman]

It is up on the throttle body. It is called the Throttle Position Sensor. Although, there is another possibility. Is your speedometer reading correclty? The rear speedo sensor in the rear end also can cause some problems simular to that. The E4OD will judge load by how much throttle you are giving it (TPS sensor), and the speed for which you are traveling (speedo sensor). I would say the TPS sensor first though.

[stump puller]

I don't know if speedo is reading correctly, probably not with oversized tires but won't the computer compensate for tire size? To fix the tps is that adjustable or must you replace the sensor? I'd rather fix this my self than take it to dealer, Thanks!