2000 Buick Lesabre 6 cyl Front Wheel Drive Automatic 70,000 miles
The transmission no longer shifts from 3rd gear into 4th (or overdrive). I didn't notice this until one day I was driving to my son's and happened to look at the tac and the engine was turning at 2000 rpm's driving at the speed of 55 mph. I have an appointment at the Buick dealers sevice shop in the morning. I called the service manager and he said it could be a thermostat or something else not too expensive. I'd just like to know what you think it could be.
Thanks in advance.
A bad thermostat could be the problem. The transmission will not shift into overdrive unless the engine is at operating temp and if the thermostat is stuck open then it will not reach operating temp but usually the check engine light will come on and set a code. Otherwise you will have to rebuild transmission. Lets hope for the best. That transmission will cost about $1500 to $1800 to completely overhaul.