flashing overdrive light and harsh shift

[weilertrans]

I have a 91 f250 7.3idi and the od light starts flashing and athe trans shifts harshly from 1st to 2nd but is ok going up the shift sequence. I've scanned it and get a excessive torque convertor pressure message and if i clear the code it shifts ok until the light starts flashing again. The light may come back on right away or stay off for days or even weeks and it seems that weather has some effect. If it is raining i have more trouble and if it is cold and i start to take off it seems that something is in some sort of lock up. May be my imignation and is only very slight and really could be normal but i have been in the heavy truck maintenance business for 40 yr and notice such thing more than the average person. I replaced the trans last year with one that was freshly rebuilt at a professional trans shop. I installed the torq that was with the trany BUT it wasn't freshly painted and actually questioned the "Rebuilt" status that i was told but installed it anyway. Trany was ok for 6-8 months with no problems. I've had numerous suggestions regarding electrical issues but haven't found any. Any help? Thanks and Merry Christmas!!!!

 

[sassyrel]

need to pull the codes---but you dont have in your avatar what year the truck is---pull the connector on the right side of trans,and check for corrosion or water---could be the mlps on the left side of trans going south also, or the sensor on the side of the ip out of adjustment--

 

[LCAM-01XA]

Merry Christmas to you too! About the trans, the moment you mention she acts up when it rains the light bulb in my head lites up bright - electrical issues. You say you haven't found anything wrong there, but really what you're looking for is hard to notice - water getting in the connectors and partially shorting them out internally. You need to pull every harness connector off the trans, blow both the harness and the transmission parts of these connectors clean (they sell electrical contacts cleaner for that, it's a spray much like carb cleaner only not as aggressive on everything), then pack all connectors good with dielectric grease, and plug them back like they were. You have three connectors at the trans (VSS in the back, MLPS at the shifter lever, and solenoid pack on the passenger side under that heat shield). There are also three more connectors where that harness plugs into the body harness up in the engine bay on the driver-side inner fender under the brake booster - these are right next to each other, maybe even all attached to a common bracket (which is the factory arrangement), you need to clean and grease them good too.

 

[LCAM-01XA]

need to pull the codes---but you dont have in your avatar what year the truck is---pull the connector on the right side of trans,and check for corrosion or water---could be the mlps on the left side of trans going south also, or the sensor on the side of the ip out of adjustment--

You my friend, you need your morning coffee - he said '91 F250 right in the beginning of his post

 

[topgunn]

If you haven't found the problem, check brake system. It can be as simple as the brake switch to a bad ground somewhere. Also any where in cruise-control system, as it locks and unlocks t/c. If you can't find problem- swap to a ZF5, like I did.

 

[sassyrel]

You my friend, you need your morning coffee - he said '91 F250 right in the beginning of his post

since its Christmas--ill let this pass--

 

[trackspeeder]

You might want to check the transmission computer. They can get flaky when wet. You will find it next to the e brake.