my transmission keeps going from 3rd to 4th. I was gogin 85 down the interstate the other day and it kicks back from 4th to 3rd. at 3rd its goverend to 72MPH. what makes it do this.

 

Assuming your talking about an automatic transmission?
(if not, you gotta stop downshifting there )

What year vehicle?

What rear end gearing, what size tires?

It is actually shifting out of overdrive.
This could be due to any number of reasons, depending on year of vehicle.



phox

 

Its a 92 automatic. Dana 60 rear end. Normal size tires. everythign shuold be ok. the guy we bought it from said spray WD40 on this black peice on the pump but that didnot fix it.

 

92 is too old for me.

Plastic piece is probably the TPS, most likely it has outlived itself.

Hopefully others with more experience with the old automatics will come back from the holiday and chime in.


phox

 

I don't own a first gen, but from what I've read it sounds like the TPS. That black piece on the pump is the TPS. With the truck off, tap on it with a hammer while working the throttle back and forth, this might get a few more miles out of it.

 

heres some reading on how to clean the tps
saves you some 250 bucks

https://www.dieseltruckresource.com/...&highlight=TPS