Although it looks like a terrific...
Although it looks like a terrific wedding band for a gear head, this delicate looking piece of "jewelry" is the Low/Reverse roller clutch. It looks identical to the L60's but GM says it's a heavier-duty component designed for the L65's higher torque capacity.
Two versions of the 700-R4 appeared: one with a 60-degree, bellhousing bolt pattern and another with a 90-degree bolt pattern. And though the advantages of lower cruising rpm and higher fuel economy were widely praised, the early 700-R4s suffered from weaknesses that caused many to fail in even the lightest-duty applications.
By the '87 model year, the 700-R4 had been internally upgraded and the demons that caused many a burned-up transmission had been exorcised. In the '90s, the name changed to 4L60, reflecting GM's new nomenclature for all its transmissions - "4" for four-speed, "L" for longitudinal (rear-wheel drive), "60" denoting the torque capacity rating. (The "E" was added when the transmission was converted to electronic control.)
But while the name of the transmission changed (probably to make wary consumers forget about past 700-R4 problems), the design was the same. The 700-R4 and 4L60 are internally similar, including gearing.
The 4L60-E came along in the mid-'90s, and shortly thereafter its design was changed from a three-piece construction to a two-piece design. Currently, the L60 and L65 have a separate, 360-degree bellhousing, which completely encloses the torque converter. This was done to increase powertrain stiffness and reduce vibration.
For stronger 3-4 shifts, the...
For stronger 3-4 shifts, the 4L65-E's 3-4 clutch pack has seven friction plates. The 4L60-E's 3-4 pack has just six plates.
Electronic versions of the transmission also use an electronically-controlled capacity clutch, instead of a mechanical lock-up clutch. This design lets the computer decide on the necessary amount of slip, which maximizes fuel economy.
As for the 4L80-E and L85, they are descended from an even older GM transmission, the Turbo 400. Essentially, the L80 and L85 are Turbo 400s with an overdrive gear and electronic controller. Of course, the Turbo 400 is merely a heavy-duty, slightly longer version of the venerable Turbo 350.
The names may have changed, but the transmission cases didn't. -BK