Transmission Slipping

Truck seemed to be working fine until I descended about a three mile steep dirt hill. Truck was in 2WD and I was alternating between first and second gear.

Back on the paved tode the transmission started acting like it forgot how to work. Revs would come up with no power. Seemed to be searching for the correct gear.

Pulled over, turned off the truck first about 15 minutes and then started it back up again.

Then it ran perfect. Shift points and power returned. Did great up a couple long hills in UT. Easily held 75 plus on the freeway. For about 125 miles. Then it started slipping again. Almost no power but will hold speed without hills.

Shut truck off, works fine.

Any guesses? Fluid level or quality?

 

Three mile steep climb? Heat.

 

Sorry... I wasnt clear... descending in low gears

 

That's my bad for not reading your post more carefully. Not sure what to tell you as nothing comes to mind.

 

Have you ever exchanged the factory transmission fluid?

 

I honestly don't know the service history on the truck.

I have not changed it for the 15K I have had it... the truck has 170K on it.

 

170K and thirteen years old, I’d say you’re way overdue for trans fluid. Hopefully no damage has been done.

 

I would agree... but I am not saying 170K with no change is the case... i just don't know.

Would old fluid slip like that... or would the actual levels need to be off?

Would you get the transmission flushed at this point... or just try new filter and fluid?

Its my understanding that flushing high mileage transmissions can cause more harm than good...

 

Sorry. I can only add this, https://www.google.com/search?q=sli...VJDQIHfetDlUQrQIoBDAAegQIAhAL&biw=360&bih=616
lots of threads on slipping trannys

 

Old fluid will absolutely cause this, or cause abnormal wear/damage that will cause it.

At this stage, assume it was never changed. No flush, do a drain and refill, change the filter, pray.

 

There's not enough information to proceed intelligently forward at this point.


Fresh ATF contains additives that protect the components inside the transmission
Time kills these additives
Heat kills these additives
Once the ATF is flowing without additives, components wear at an accelerated rate
However, fluid still exists in the closed system so the hydraulic action of the automatic transmission still functions
Slipping in a transmission could be due to worn frictions or valve body problems


Supposedly fluid that has never been changed contains the microscopic debris from worn friction plates, which allows the transmission to "feel" like it's working correctly. People will then do a line flush of the fluid, and shortly after begin complaining of slipping.

If you are inclined to do a fluid change, I'd recommend only doing a drain from the pan with the engine off. This will replace around 3 quarts of WS ATF and leave behind some of the old stuff. You'll gain fresh additives from those 3 quarts, which could help if the issue is sticking valve body components, since the additives include detergents that clean. You can keep draining 3 quarts at a time this way, which is the safe approach, but give yourself time to drive a few hundred miles between each drain to gauge if you can keep doing it.

 

There was a Toyota overfilling procedure to raise the pressure in the tranny so it didn’t stay in neutral and jam into gear. I’d just try changing your fluid and filter(do the whole drivetrain). I just had a shop do mine and it works perfectly and they didn’t use the overfill procedure that the dealer did years ago...