GM also changed the tailhousing from a four-bolt to a six-bolt design.The 4l65EStock 4L60Es are rated at 360 lb-ft of torque.By 2001, engine output had increased to the point that further internal modifications were needed for Corvette, Hummer, and some other applications.
On paper, its specs looked pretty good: The trans had lower First and Second gears (3.06 and 1.63, respectively) than other automatics, its lockup torque converter offered potential fuel-mileage gains, and the 0.7 overdrive decreased the overall drive ratio by 30 percent.
These included the introduction of a pulse-width-modulated torque-converter lockup function on some models starting around 1995.
This smoothes out the converter lockup function by pulsing the apply function using a PWM solenoid.
But the original design was not considered a strong transmission, with failures behind even a mild 350 not uncommon.
The trans was so weak that in its original setup, GM deliberately calibrated it to kick out of lockup and high gear under full-throttle, top-end conditions to avoid burning it up.