Almusafir,
Welcome to the forum...
Please post your .tun file (do
Go Advanced->Manage Attachments, and then Browse, Upload).
When this condition is present (no 3-4 shift after 4-3 WOT), do you get these shifts:
- 3-2 kickdown (WOT)
- 3-2 part throttle (PT)
- 2-1 PT
- 1-2 PT
- 2-3 PT
If you get thes other shifts, then possibly the 3-4 shift valve may be sticking.
Attached page is from the 4L80E Technician's Guide.
When this condition is present, monitor the GM.GEAR and use the BiDirectional controls to command 1st, 2nd, 3rd, 4th;
does GM.GEAR show each of these being commanded...?