Strange Overdrive Issue on A343F transmission (97 80 Series) (1 Viewer)

[manunavasd4x4]

This problem started about a year ago but it was so rare that I couldn't get much info on what or why but it's happening more and more often that I'm starting to get an idea of the problem.

I'd be driving in the highway over 70 mph (hasn't happened under that) and everything seems fine; if I decelerate for a couple of seconds and accelerate, I feel like the transmission goes into neutral
-RPM'S goes all the way up
-SPEEDO goes all the way up, kinda like in sync with tach
-Will not get out of that "limp mode" for about 10 seconds or if I dont press the OD button

After this happens, it goes back to normal like nothing happened and will not do it again for days/weeks or it could do it again 30mins later.

I'm trying to find someone that has seen this happen before in hopes of finding a fix for this instead of replacing or rebuilding the transmission.

 

[cjmoon]

Sounds to me like torque converter slip. Fluid full. That’s the first to starve.

hot in N flat ground.

tps could have a bad spot where the trans isn’t happy. It only sees it in odd conditions. Just an idea.

 

[jonheld]

-RPM'S goes all the way up
-SPEEDO goes all the way up, kinda like in sync with tach
-Will not get out of that "limp mode" for about 10 seconds or if I dont press the OD button

Does the engine RPM actually go"all the way up" or does the tachometer just read it incorrectly?
If the speedometer and tachometer go "all the way up" together, then there is an electrical issue.

 

[manunavasd4x4]

Does the engine RPM actually go"all the way up" or does the tachometer just read it incorrectly?
If the speedometer and tachometer go "all the way up" together, then there is an electrical issue.

No, it doesn't go all the way up. The tach is fine but the speedo "mimics" it when this happens.