89 auto trans problem

[Saskjeeper]

I have an 89 Leredo 6 cyl. with automatic transmission. It usually runs great, but once in a while it doesn't want to shift between 2nd and 3rd gears. the RPMs will shoot up, but it won't shift gears. I either have to pull over to a stop, and go again and its fine, or on a busy street sometimes punching the accelerator works. Any ideas on what might be causing this?

[Saudade]

Check your throttle position sensor (TPS). My '88 had flaky 3rd-4th shifts. Changing it, fixed the problem.

You can search the forum for TPS and find a lot of posts regarding this.

[89ltd]

also speed sensor will cause same problem

[1more88XJ]

saskjeeper, You might want to change your trans oil and filter, it isn't to hard and it might help on your gears changing on those once and a whiles, also add some lucas trans fix it also helps to coat the gears better and keeps the trans oil from breaking down.