4T65E Transmission Info 
 

 
This page provides information about the GM THM-4T65E 4 speed Automatic fwd transmission/transaxle which is found in many 1997 and newer vehicles equipped with the 3800 engine and most 2000 and newer vehicles with the 3400 engine.  This is a great trans and has been refined a bit over recent years and as many of you know has its shortcomings, especially when the mileage gets high or extra power is added. 
If you have a question about something that you do not see on this page feel free to send us an email for more detailed information.

This transaxle is a fully automatic and electronically controlled.  Shifts are all controlled by the pcm by two shift solenoids, line pressure is also fully electronic and controlled by a Pressure Control Solenoid, or EPC which is commanded by the pcm.  This transaxle also employs the use of a Torque Converter Clutch, or TCC and is used to further enhance gas mileage and keep engine rpms lower.  The TCC style in this trans is a PWM type, which stands for Pulse Width Modulation.  This style PWM TCC system was developed to allow for a smooth engagement of lockup and allows constant slippage of the TCC and can apply in 2nd through 4th gears.   The constant slippage is tolerable to the converter because of a special TCC lining developed especially for this purpose and is called a Woven lining.  An ordinary TCC clutch would burn up and shudder vilently if used in this type of system.

-Below are the gear ratios for each gear of the transmission

1st  2.92:1
2nd  1.56:1
3rd  1:1
4th (OD)  0.70:1
Reverse  2.38:1

There are numorous gear ratio combination options for the 4T65E transmission and below are ratio options that can be found

-Final drive-differential ratios
    
    2.86:1 in standard differential only
    3.05:1 in standard differential only
    3.29:1 in standard differential and also the HD (Heavy Duty) and Volvo version differential

-Drive and Driven sprocket combinations and ratios

    33 Drive / 37 Driven creates a 0.892:1 ratio
    35 Drive / 35 Drive creates at 1.000:1 ratio
    37 Drive / 33 Driven creates a 1.121:1 ratio

The Drive and Driven sprocket ratio will directly factor in to calculate the overall transmission ratio.  For example most of the Supercharged 3800 powered vehicles come with a 3.29 HD differential but they have a 37/33 sprocket orientation and this will overdrive the transmission and create an overall ratio of 2.93:1



-Here are the resistance specs on the internal solenoids

Connect Pins   Solenoid         Resistance at 68*F   190*F                   Shift Solenoid Patterns for each gear

   A-E                1-2 Shift Solenoid               19-24      24-31                   Range      1-2 Solenoid   2-3 Solenoid
   B-E                2-3 Shift Solenoid               19-24      24-31                     Park               ON                  ON
   T-E                TCC/PWM Solenoid             10-12      13-15                   Reverse            ON                  ON
   C-D                EPC Solenoid                       3-5          5-6                     Neutral             ON                  ON
   S-V                Input Speed Sensor        893-1127 1132-1428             1st Gear           ON                  ON
   M-L                TFT Sensor                    3164-3867  225-285                2nd Gear          OFF                 ON
                         Output Speed Sensor             981-1864                       3rd Gear           OFF                 OFF
                                                                                                              4th Gear           ON                  OFF
Below are the Torque Specs for the 4T65E