I disassemble the valve body from the 1994 4L80E that came in with harsh upshifts, layout all the valve trains and discuss related issues, concerns.

Tech Notes: ATSG states the wiring harness changed in 1993; torque compensator valve eliminated after 1993; however, if you have a 19911993 model year unit that has the earlier harness/VB, you can install a Rosta harness, part number 34446AK (works on all years 19912003), updated BW nonvented 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 SK4L80E shift kit instructions on how to do this procedure: https://res.cloudinary.com/transgo/wb...