Hello all, I have read this is a great site to ask questions on these trucks. I have a '99 rodeo with the 4L30E auto with a strange problem. Sometimes it will stay immobile and not shift down from 4th gear. I can select L manually and it will move.


This issue happens intermittently and only on the first drive of the day. I can turn off the car and wait about 20 seconds. When I turn it on again, the transmission shifts. PERFECTLY!

Read it could be the shift B solenoid malfunctioning. Replaced fluid and changed solenoids and no improvement. Also adjusted band.

Read it could be range sensor. Cleaned. Shifted better but still drops out. Replaced sensor. Same result.

I know the range sensor communicates with the PCM. This issue being intermittent leads me to believe the issue may be electrical... I.E the PCM. Since this issue goes away after I shut down and turn on again.

Has anyone experienced something similar? I find it hard to believe the issue is purely mechanical... Intermittent almost always means electrical but not always. Any insight would be very appreciated.
This truck has been particular about alternators too but this alternator hasn't blown up... Yet.

Oh and no check engine light or AT light.

Thanks guys and gals. I really don't want to get rid of this thing.