I tear down and inspect a 1994 2WD 4L80E transmission that came in with extremely harsh 2nd and 3rd gear upshifts and explain the cause of this symptom pattern. I also go over a range of related topics including an overview of these transmissions, model year identification, vintages, changes and interchange as well as points of inspection for each part and/or sub-assembly.

Tech Notes: ATSG states the wiring harness changed in 1993; torque compensator valve eliminated after 1993; however, if you have a 1991-1993 model year unit that has the earlier harness/VB, you can install a Rosta harness, part number 34446AK (works on all years 1991-2003), updated BW non-vented solenoid and adapt the VB and plate to work with the updated EPC (See Transgo link for instructions below). Valve bodies that use the initial vented electronic pressure control solenoid (EPC), produced by Bosch, will need to be adapted to work with the updated Borg Warner/Holly EPC. See page 5 of Transgo's SK-4L80E shift kit instructions on how to do this procedure: https://res.cloudinary.com/transgo/wb...

The front planet will interchange between 1991-1998 units but not with 99+

The video is long, I get far into the weeds on many aspects of these transmissions (much longer than I had originally planned) so feel free to break it up per the chapters below:

Overview - 0:00
Model Year ID and Walk-around - 5:11
Exterior Parts Removal - 9:51
Case Belly - 23:21
Internal Case Evacuation - 59:00
Rear Gear Train Inspection - 1:22:02
Drums and Overdrive Set - 1:42:00
Pump Disassembly - 2:13:18
Summary & Next Steps - 2:23:33

4L80E Automatic Transmission Service Group manual PDF: file:///Users/nicholasnuciforo/Downloads/4L80E%20ATSG.pdf