1998 Chevy Silverado V8 Four Wheel Drive Automatic 147000 miles
I had my transmission rebuilt about 20,000 miles ago and it is working fine for the most part. Occassionally when it shifts into overdrive just after I accelerate rapidly enough to cause the transmission to downshift, there is a noticeable vibration conincident a 'service engine soon' light. The vibration stops after a few seconds, and the service engine light goes out after a day or two. It's done this maybe 4 or 5 times since the tranny rebuild. The U-joints are original to the truck but don't have any obvious slop.
Recently, I towed a trailer about 1500 miles. When I was going uphill and the tranny downshifted, I got the 'service engine light', and it flashed for a few seconds when the engine was really working hard. The light has been on steady since (maybe 1000 miles ago).
The transmission fluid level is normal and looks clean. Transmission seems to be operating normally, and I haven't had the vibration since the light came on this last time.
Suggestions? The transmission rebuild is no longer under warranty.
1st step is getting the codes
when check engine light is on codes is stored in the PCM
sorry to say but it sounds as its a tranny issue
possible sensor or solenoid
need the codes to pin point the troubled area
need an OBDII reader to get the codes for know
most local part stores and or repair shop should be able to help some do it for free check around in your area
(auto zone used to have this service available for free )