# Auto-downshifting **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** chevrolet, s-10\ **Created:** [November 9, 2009, 10:49pm UTC](https://community.cartalk.com/t/auto-downshifting/39254 "2009-11-09T22:49:28Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![fleeingIndiana](https://avatars.discourse-cdn.com/v4/letter/f/d6d6ee/32.png) [@fleeingIndiana](https://community.cartalk.com/u/fleeingIndiana)\ **Post date:** [November 9, 2009, 10:49pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/1 "2009-11-09T22:49:28Z")
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? Thanks. ---
**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\ **Post date:** [November 9, 2009, 11:18pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/2 "2009-11-09T23:18:13Z")
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. ---
**Author:** ![transman618](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/transman618/32/24_2.png) [@transman618](https://community.cartalk.com/u/transman618)\ **Post date:** [November 10, 2009, 6:11am UTC](https://community.cartalk.com/t/auto-downshifting/39254/3 "2009-11-10T06:11:32Z")
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. transman ---
**Author:** ![fleeingIndiana](https://avatars.discourse-cdn.com/v4/letter/f/d6d6ee/32.png) [@fleeingIndiana](https://community.cartalk.com/u/fleeingIndiana)\ **Post date:** [November 10, 2009, 5:43pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/4 "2009-11-10T17:43:04Z")
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. ---
**Author:** ![transman618](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/transman618/32/24_2.png) [@transman618](https://community.cartalk.com/u/transman618)\ **Post date:** [November 11, 2009, 11:41pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/5 "2009-11-11T23:41:52Z")
Need to scan for codes first. How is the 1-2 shift?? transman ---
**Author:** ![fleeingIndiana](https://avatars.discourse-cdn.com/v4/letter/f/d6d6ee/32.png) [@fleeingIndiana](https://community.cartalk.com/u/fleeingIndiana)\ **Post date:** [November 11, 2009, 11:59pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/6 "2009-11-11T23:59:28Z")
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. ---
**Author:** ![fleeingIndiana](https://avatars.discourse-cdn.com/v4/letter/f/d6d6ee/32.png) [@fleeingIndiana](https://community.cartalk.com/u/fleeingIndiana)\ **Post date:** [November 12, 2009, 2:04am UTC](https://community.cartalk.com/t/auto-downshifting/39254/7 "2009-11-12T02:04:27Z")
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. Thanks. ---
**Author:** ![waterboy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/waterboy/32/764_2.png) [@waterboy](https://community.cartalk.com/u/waterboy)\ **Post date:** [November 12, 2009, 2:55am UTC](https://community.cartalk.com/t/auto-downshifting/39254/8 "2009-11-12T02:55:46Z")
Assuming of course you are not using cruise control. ---
**Author:** ![transman618](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/transman618/32/24_2.png) [@transman618](https://community.cartalk.com/u/transman618)\ **Post date:** [November 12, 2009, 3:10am UTC](https://community.cartalk.com/t/auto-downshifting/39254/9 "2009-11-12T03:10:28Z")
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. transman ---
**Author:** ![fleeingIndiana](https://avatars.discourse-cdn.com/v4/letter/f/d6d6ee/32.png) [@fleeingIndiana](https://community.cartalk.com/u/fleeingIndiana)\ **Post date:** [November 12, 2009, 12:57pm UTC](https://community.cartalk.com/t/auto-downshifting/39254/10 "2009-11-12T12:57:40Z")
Thanks. Will do.