I have a 1995 Dodge Ram 2500 with 312,000 miles and whenever the temperature is below about 40 degrees Farenheit the torque convertor will unlock and lock back up. However when the temperature is above 40 degrees it does not do it at all. Does anybody have any ideas why it would be temperature related?

 

My owners manual said the converter wouldn't lock until the trans reach 40 degrees. I found out that most of my trouble was from the throttle position sensor being dirty inside. Got to assume the dirty TPS was confusing the computer because, as soon as I changed it, everything was back to normal. There's a way to clean the TPS but, I've never done it, maybe try a search for TPS cleaning.

 

I actually cleaned the tps already(still unlocks) and i dont understand why if it is a dirty tps why it only does it under 40 degrees?

 

Your tranny temp sensor may be acting up. Easy way to check it is to unplug the cable to the sensor and jump across the wires to the PCM with a 1000 ohm resistor- Radio Shack 25¢. The sensor is located on the hot line to the cooler, driver's side a little forward of the tranny.
If the resistor does the trick sender is the problem. Replace the sender or just leave the resistor in place.

I've been assured by a couple of tranny gurus that not having an operational sensor will not hurt the tranny in the cold but you should have a sender that works or an aftermarket gauge to warn of high temps.

 

if it is to do with the temp circuit, OD should also be affected, and I believe my DC manual calls 59* the magic number.

 

Under 40, goodness, we are still trying to get under 70 so the air can go off at night...

 

59F is the number for the block heater. Don't recall the exact temp for the tranny to shift into OD but believe it's in the 70s. Unless it's below 40 it will reach this temp very fast, you won't notice the loss of OD unless you live at the base of a freeway on-ramp. The sender is in the hot line, it will start seeing heat the second you go out of park. About the longest I've had to wait to shift into OD was two miles when the outside temp was minus 30°.