I have a 95 850 GLT auto trans. The trans will drive fine then the yellow arrow light comes on and the trans starts to slip, eventually no gears at all. This occurs over about a 2 to 3 mile distance. I check and clear the ODB codes and it runs fine again for about 2 to 3 miles. The code states wrong gear ratio (P0740?)

 

Further, I neglected to mention the car has about 150,000 miles. I flushed the fluid due to water leaking into the trans via the radiator trans cooler. Radiator has been replaced. This problem started after I discovered the water leakage issue. Also the OBD code is P0730- gear ratio incorrect. (not P0740)

 

Sorry to say but the tranny is most likely smoked.
The coolant destroys the tranny.

 

I don't understand whywhen I clear the code, the transmission operates fine.

 

Usually because it doesn't take long for a problem to show. When you clear the code the computer thinks things are fine till it see the fault again.

 

If clearing the codes allows the transmission to function normally then I must assume the transmission mechanicals are OK. The fault code itself is electrical (Digital) so I'm feeling that the problem may be an electrical component or the engine/trans control unit?

 

I would check for correct fluid level. My 850 used to do it when the fluid was low by as little as a half quart.Make sure to use Dexron-III/Mercon, and synthetic fluid isunnecessary for these gearboxes; the cheapest name-brand's fluid would be fine.


JPN

 

I would also check the fluid (Possibly flush it again just in case there is still some small amount of coolant contamination) but I too think Tech is correct, the tranny is probably toasted.

Glenn

 

The fluid has been flushed twice and is the proper color; the level checked and corrected.

 

The coolant eats the clutch material.
So I will bet it is driving fine but slipping enough to kick the code after the short drive.