Here is what i was able to find on the net:
By the '87 model year, the 700R4 had been internally upgraded and the problems that plagued earlier versions of the engine disappeared. 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.) The 700R4 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.
The 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.
Hope it helps,
Chief Operator A.R.S. N8PHU
ET1(SW) U.S.N. (Retired)
#1 Electron Wrangler
Father of 7
Former restorer/owner of 1976 Pontiac Trans Am
Pontiac 400 , TH350 tranny, and way too many tires....
Last edited by N8PHU; 10-27-2004 at 10:27 PM.