Keeps dropping out of OD when warm....

[7FA]

Need some help here. Have a 93 CTD w/ auto transmission. Past few weeks I've noticed that the transmission want to kick out of OD when I let off the gas at50+mph, but as soon as I gave it gas it would drop back in. I adjusted the TPS per the SM and the reading were within specs (. 85vdc at idle). Weird thing is this seems to only happen once the transmission is up to operating temp.



Well today the transmission started dropping out of OD at 70mph unless I get my foot in it pretty good. I pulled over and tried to tweak the TPS adjustment some, but I could not seem to get it any better.



Any suggestions??

 

[dan brooks]

Try cleaning the connections on the temp sender, speed sender, and TPS, then use dielectric grease on them before reconnecting. That normally solves about 90% of my overdrive problems for a while.



It may also be the temp sender in the transmission line. It is supposed to kick the transmission out of overdrive when it hits a certain temperature (~280* - after damage is already done). If cleaning the connections doesn't solve the problem, try using a jumper to bypass the temp sender. The temp sender is a dealer-only item and isn't cheap, so I'd avoid throwing money at a new one until you can be sure that is the problem... .

 

[cerberusiam]

First clean all the connections and grease them then try it again. Not all TPS/PCM's like the . 85 for a setting. Try testing from . 85 to 1 volt at rest and see what reactions you get. Two things could be causing what you describe; the voltage is too low when you are cruising and causing the down shift, or, the solenoid that runs the OD shift can come loose and leak so when the trans warms up the OD doesn't want to hold. The speed sensor starting to go south will cause the same symptoms and if al else fails try replacing it. You will not see a bounce in the speedo but the signal is off enough to cause the hunt in and out of OD.

 

[7FA]

Thanks for the tips guys. I'll give them a try tomorrow and report back!!