I've got a 97 4x4 5.2L Magnum with automatic, and the overdrive is inconsistent in engaging. I just had the trans serviced (fluid, screen change, etc.). When cold, the overdrive engages as it should and I'm cruising at 50 mph (the speed limit here on the island) at 1,500 rpm. When the motor/trans gets warmed up, however, it gets stuck in regular high gear and won't engage the overdrive, and I'm cruising at 50 mph at 2,250 rpm, and sucking fuel. The O/D switch does not seem to have any effect one way or the other (no indicator light, either). Bought the truck last week from a private party, and happy with it overall. Can't seem to figure out this issue, however. Any thoughts?

 

I had a similar issue.. Overdrive Solenoid in the Tranny.. The first time, I didn't get a light. And now and then, when OD engaged, it would rev up and down, up and down, when I wasn't pushing it. If I pushed the gas, it would stop. Replaced the Solenoid, and it worked great. Then, I had the front band replaced, and it started again, this time popping a P1740 code, so I replaced it, AGAIN... Fixed the issue, light went away.

 

Mahalo (Hawaiian for thanks) RaissiKitten...was leaning toward that as well, although I don't have the surge problem...just the inconsistent in and out with the OD. It's a relatively cheap fix to try.

 

Relatively.. Be cheaper if ATF4 was cheaper. LOL. But, at least you get a good filter and fluid change if nothing else. Something else you might look into while your in there, Is getting some electrical parts cleaner and cleaning the governor solenoid and pressure sensor off. They get kinda nasty after some time. Good luck. I hope it fixes your issue!