Trans shifting in & out of OD
 

Totally new to the forum, not a mechanic but can follow directions well, any help greatly appreciated. Yesterday on a trip over mountain pass in the Cascades the trans. began shifting up and down, 3rd to OD and back with any change in power. Didn't matter going uphill, downhill. Up until then, truck shifted to OD ~60 mph unloaded and could pull most grades without shifting. Took it for a spin this a.m., shifts back and forth at any speed 40 -60. OD off switch works to eliminate shifting at slow speeds. This is a stock 92, no mods whatsoever, 107K miles. Transmission serviced 10K miles ago. Any ideas where to look this long weekend? Thanks. :confused:

Have now thoroughly searched this site, what a great resource. Am starting with TPS cleaning and checking.

the cleaning and re electricle grease everything fixed mine. jiMMy

Here's how I fixed mine - cheap and worked great

https://www.dieseltruckresource.com/...threadid=42003

Thank you Mr. Ouchman. I like the idea of a cheap fix. Can you tell me what the potentiometer does with the signal, send a set voltage? I'm going to try the adjustment first, now that it's clean it seems to work but has low voltage at rest. Thanks for the help.

here hope this helps http://www.piersdiesel.com/Tech1GTPS.htm
also put in a signature so we no wat you got

I know absolutely nothing about electronics. Only enough to understand what they're doing. I understood that the potentiometer was a cheaper version of the one in the TPS (throttle position sensor). I figured if I controlled the adjustment on the POT then I could "dial in" the shift point. I was right - it worked great. I no longer have the truck, but there is no reason for it to fail. If you tow a lot you might find that adjustable shift-point is very handy. Good luck!