2003 gmc 3500 allison transmission torque converter relief spring kit

A few common causes are low or dirty transmission fluid, or faulty shift solenoids. The transmission uses fluid pressure to shift the gears, and does so using electronic solenoids. If there is an issue with either of these the vehicle may experience problems shifting or transferring power to the wheels. If these are not the problem then it could be possible that the transmission is having internal faults, perhaps a worn torque converter, or transmission gears, inside of the transmission. As issues like these can sometimes be difficult to diagnose, if you are unsure, I would recommend having a professional technician look ay it.

I don't know a "trick" but there are some youtube videos regarding allison transmissions.

Thats a Tfp switch malfunction..replace solenoid and torque converter. That should fix the problem.

I suspect transmission oil drain back to oil pan during night.
if you want to confirm.
engine stop take oil level place a mark on dipstick then let it sit overnight. in the morning take oil level if it raise then oil have to charge the torque converter you hear a cavity front pump noise.
when hot take oil level engine hot in park have to be at top of oil level

The P0700 is just a generic code to tell you to look for more specific transmission related codes.

The P0743 indicates a problem with the TCC (torque converter control) circuit. That can be the solenoid itself, the control module, the torque converter or any related wiring. You need a transmission specialist to look at that.

http://www.makcotransmissionparts.com/Chevrolet-GMC.html
you are stuck with the Allison 1000 tranny.

They will deefinitely providing the 2 are the same model. In 2004 the Allison tranny was available in a 5 or a 6 speed. Before 2004 only the 5 speed was used. If one is changed for the other there will be shifting issues and codes set in both the ECM (engine control computer) and TCM (transmission control computer). Make sure you are putting in a 5 speed Allison tranny.

there is a solenoid that turns it on and off, it (the lock up part) works by pressure. There is not a magic switch or valve that will turn it off. Most of the time a new torque converter is the only fix, but not always. Allison is a different bird than the GM trans. GM let us fix that at the dealer Allison would have us pull it and replace it.

Her is the definition and a list of possiable causes.


Code P1740-Torque converter clutch did not lock up when the PCM sent the command. Enabling conditions: No engine or transmissions codes are present, vehicle speed was under 70 MPH, TPS was under 33% open. When the PCM commanded the torque converter to lock, no change was detected in engine speed. Blocking action: This code can block the following monitors: none.
Testing: Check torque converter solenoid for proper operation.
P1740 TCC O/D SOL PERFORMANCE (GAS)
Theory of Operation
The Torque Converter Clutch (TCC) Solenoid is used to engage the TCC which improves fuel economy.
When Monitored
The Torque Convertor Clutch (TCC) and Overdrive Clutch (OD) will be tested each time the PCM requests TCC engagement in 3rd gear and OD.
Set Condition
The DTC will set if the expected RPM drop is not achieved while attempting to engage TCC or OD. This indicates a malfunctioning torque convertor or overdrive clutch.
Possible Causes
* ENGINE DTCS PRESENT
* TRANSMISSION DTCS PRESENT
* TRANSMISSION TEMPERATURE TOO COLD
* OIL PAN CONTAINS EXCESSIVE DEBRIS
* 3-4 SHIFT SOLENOID
* SHAFT OR SEAL DAMAGE
* TCC SOLENOID
* TORQUE CONVERTER

I assume that you have an automatic transmission, It sounds like your torque converter is the culprit here. The TC is what allows your tranny to be in gear, but not stall out the engine (you probably know this already). If your TC is "locked up" all of the time, it will cause the stallout that you describe.

Good Luck

Brian