Transmission Hot Mode

[jeffreydmet]

In digging through my Helm Service manual I come across a single statement about how the thermistor in the transmission will put the transmission in "hot mode" and lock the TCC in 2nd. It is really not very specific on what all hot mode entails. Hot mode is supposed to set a history code in the computer but does not turn on the SES.
I put a switch with a 50 Ohm resistor (this tells the PCM that the trans is about 300 deg F) in parallel with the transmission thermistor to force it in hot mode. The manual says it takes 10 min to set hot mode. It seems to be more agressive with the TCC use like I want it but I have not towed with it yet to see how that acts.

Does anyone out there know what all running characteristics change in hot mode and am I likely to cause any problems running for extended periods in this mode? All I could find for sure was that the shift pressure adapt freezes during hot mode.

[turbovair]

Why do you want to do that? What is the benefit of forcing it into hot mode?

[HowieE]

Are you sure your mode is in fact locking the convertor and not just increasing the line pressure?
My first guess about Hot mode would be it is another term for Limp Mode and is intended to protect the trans under some conditions such as overheating. If this is the case what is happening is the trans line pressure is increased from about 90lbs to about 140lbs. thus reducing slippage at the clutch plates that may be causing the overheating.
Yes this will result in more agressive shifting through the gears in a functioning trans and if not towing feels like a trans kit has been installed. However while towing the shift from 1st to second feels like it would like to twist off a u joint.
My BD Torque Loc cause the limp mode problem and I have more than enough experance with towing under these conditions. It is not something I would recommend as a long term situation.

[jeffreydmet]

The goal is to use the TCC in 2nd on long hills towing.

My GM service manual list for DTC P0218 (transmission fluid overtemp) says that if this code appears that the action taken is to freeze shift adapts and store this code in history.
Under DTC P0712 which is a temp circuit low (occurs for a short or very high temps) increased line pressure will be commanded and shift adapts frozen.

Under DTC P0741 TCC system stuck off it has a statement "The transmission must be in hot mode or experiencing a wide open throttle maneuver in order for the TCC to be commanded ON in 2nd and 3rd gear"