Does any one know why the transmission temperature gets higher while the engine is off "auto stop". assuming there are no moving component in the transmission while parked.

I have been experiencing higher temperature while parked than climbing a mounting. 64 degree when start and stays in the 170 range during normal driving. get little low in the highway but it shoot up while parked on auto stop.

If any one can share the temp / volts


Omar.

 

I don't have your vehicle, so just based on my experience with conventional, non-hybrid vehicles we had in the past: I've found overheating often occurs after the engine has been under heavy load, when the vehicle has stopped, just idling.

For example: driving up a steep, sustained slope on a mountain, and then arriving at the entrance to the summit parking lot. If there is a lot of traffic, and a wait to get into the parking lot, this is one time we would often get overheating.

I think the reason is that while driving up the mountain the engine was high revving and under heavy load, but still the car was moving at a fair speed and able to cool more efficiently, due to good air flow through the radiator.

But at the summit parking lot, the engine is still hot, but stopped, so there is no natural air flow through the radiator.

One thing that can help if the overheating is severe is to turn the passenger compartment blower up to full and set the temperature to high. Also disable air conditioning if possible.

 

Omar: The position of the transmission oil temperature sensor is above the solenoids that control the valve body.

When the oil is not actively flowing it will read higher beacuse of the heat from these solenoids.

 

This make since, I'm going to experiment this for longer time and see if the temperature will rebound some.

 

There you go Omar

 

Left the Truck on "auto stop" for 15 min, Temperature gone up to 190 degree and did not drop.

I still don't have a conclusion on why the transmission is generating heat while on auto stop.

 

The transmission is not generating heat. A little electrical solenoid that is very close to the temperature sensor is. Since the sensor is right above an operating electrical coil it is effected by the heat rising off the coil. The solenoid is part of the 12 volt electrically controlled valve body and transmission computer. These things get hot. Ever feel the heat of a PC?

The heat rising off the little solenoid is what you see in a prolonged Auto Stop.

You can do the same experiment by turning the key to accessory first thing in the morning. Over several minutes the temperature will appear to rise.

When you start the vehicle or drive in Auto Stop... The oil gets mixed up again by the motion of motors, clutches, and gears and the little local hot spot dissapears.


Hope this helps explain.

 

Marty, I'm getting the feeling you are a bit more than a causal "enthusiast" of the GM Hybrid technology.

 

Your are rite Jason, I start to think Marty is one of the designer for two mode transmission. I honestly stopped worrying about the temperature since his last replay. lol

 

dissipating heat from metal is very hard to do. I am heavily involved with air racing and heat is the biggest nemesis to both air cooled and water cooled raicing aircraft. once they get hot they don't cool down. the cockpit of a P-51 will be 110 or more degrees an hour or more AFTER the race is over and the plane is on the ground. I think the temp is RESIDUAL in nature and remember its reading the temp at one exact spot when the fluids are not moving, so it could easily spike at that point.