When combining many of these new factory internals with the best of the aftermarket, the once-feeble 4L60E can now be transformed into a stud.
"The 4L60E certainly has its limits, but they're much higher now than just a few years ago," Mike explains.
4L60 uses a 6.5" depth bell and 4L65/70 uses a 7" depth bell .
They also have different input shafts and torque converters. 4L65/4L70 uses a 300mm input shaft and converter designed for LS applications only.
The Transgo HD2 kit comes with very stiff springs for the 22-spring cage which I estimate triples the stiffness.
(Therefore I have been using 16 HD2 springs to only double the stiffness.) Any experience with the full 22-spring HD2 kit would be appreciated.
With GM's recent updates to the 4L60E, building one that can survive behind a brutal street/strip motor is an entirely feasible proposition.
In 2001, GM upgraded the 4L60E's four-pinion front and rear planetary gearsets to more rugged five-pinion units, and renamed it the 4L65E.
Since the introduction of the THM 4L60-E transmission in model year 1993, there have been many major engineering design changes to improve durability and reliability.
These changes have affected nearly every part used in the THM 4L60-E.
Granted it's tough to shake such a miserable track record, but recent innovations have made it possible to build a 4L60E capable of handling in excess of 600 rear-wheel hp.
While we can't blame you for involuntarily convulsing in laughter after reading that last line, Mike Kurtz of Century Transmission is about to make good on that claim.
5 pin planetaries vary by application only Only corvettes and HD vehicles came equipped with 5 pins.