Your tranny is probably NOT a 4l60E, but rather a 700R4. Unless you've spent $1200 recently on computer equipment to run the 4L60E - a 4L60E is the tranny from a 1993 and newer car - it is completely computer controlled, no TV cable (what us old schoolers call the kickdown cable) - all shifts are programmed into a computer and controlled electronically - thus the "E" on the end (700R4's were also called 4L60's - no "E").
Not many here will respond to a question about a 4L60E because we all have 700R4's - only a select few have spent the cash for a 4L60E swap (given the expense for the computer to control it), and thus not many know much about them.
Assuming you have a 700R4.... Try reposting your question stating 700R4 instead - so you'll get more response.
Second - does the fluid smell burnt? If so, then probably burnt clutches. Mine was/is the same - getting a local rebuild done soon myself.
There is no easy fix, slipping is slipping - means a rebuild. Rebuild can be as much as $1200 depending on your area. You can sometimes follow a tranny guy to lunch from the shop, and ask him on the side if he does rebuilds on the side - some do and way cheaper than the shop price.
Other option (assuming your tranny is bad)....hunt down another used one. No guarantees there, but it's a cheap fix for the moment. I've been able to get them as low as $300 from local bargain trader rag - and also from tranny shops - if they don't have one around, they know someone that does. You can also try the local boneyards and yank one - again no guarantee, but might buy you a year of cash savings.
Hate to sound negative - but it never does any good to paint a pretty picture. Hope any of that helps.
1992 25th Anniversary RS T-Top
350 Carb 10:1 Dometops Mild Cam
Hedmann Headers Hi-Flo Cat/Aerochamber Muffler
700R4 B&M Shift Kit LS1 Disc Rear w/3.42 Posi
Poly Bushings Eibach Prokit Bilstein Shocks/Struts
HOK Candy Teal on Silver Flake IROC Hood