The automatic transmission in my 2000 S-10 will suddenly downshift from drive while driving at highway speed (65mph), on level roads. This occurs during trips of over 45 min. I just had the filter, gasket, and fluid changedf a week ago, thinking this would solve the problem. It didn’t.

Any thoughts on what might be causing this?


This is most likely NOT an internal problem with the transmission. It’s likely external, involving the transmission control module and its inputs (sensors), and outputs (solenoids and other actuators). A transmission shop has the tools and expertize to troubleshoot this problem.

Can you be a little more specific on “downshifting from drive”. Are you saying that the transmission is downshifting from overdrive to third gear at highway speeds. When it “downshifts” like you say, does the engine rpm’s increase by maybe 200-300 rpm’s or does the rpm’s increase like 500 or more rpm’s?? This is very important.


I don’t have a tach so it’s hard to say how many rpms. Yes, it goes from overdrive into what feels and sounds like 3rd. As thought the shift lever were on “3” and I’m driving 65mph.It doesn’t come back out of it when I reduce speed. The only thing I can do is stop at the first exit and shut the car off for a half-hour or so.

Need to scan for codes first. How is the 1-2 shift??


I don’t notice anything unusual in normal city driving, nor during short trips on the highway. It just happens at normal highway speeds after 30-40 mins of driving.

I’m not looking to fix this myself, so I don’t need a lot of detailed information. I was just wanting to get a general idea of what might be wrong so I could research the approximate cost.

Assuming of course you are not using cruise control.

Have it scanned. It could be something as simple as a TPS which is maxing out for no reason. I have seen that many times before.


Thanks. Will do.