350 Chevy

Please help. 1996 Chevy K1500 5.7 (350). 160,000 Miles
VCU will not command lock-up on transmission.
Although transmission will lock-up on scanner request
Transmission has been completely rebuilt at 160,000 miles
Replaced ECU 3.670 (part #16244210 vcm-reman) twice and replaced module 2.383(part #16208981) in vcm
Still unable to communicate with vcm. Traced all wiring to vcm. Cleaned all terminals and connection.

Chevy Dealer has had my truck from 6/13/07-7/7/07. Snap shots have been taken while truck is moving and records strange data (ex. Driving in gear 256). They have been unable to solve lock-up problem. They have suggested that the vcm needs new programming directly from G.M. engineering.

Up-grades
3in. Rancho Suspension (33x15x12.5 BFG)
K&N air-intake
Dug Thorly Tri-Y headers
Genuine Gear 4.10 front and rear with rear ARB air locker
Air Lift rear air bag system with on-board compressor
Replace timing chain and installed high-volume oil pump at 160,000 miles
Tranny rebuilt and up-graded. At 160,000 miles
H/D trans rebuild
Torque converter rebuild
Z pack, 3-4
Force motor
Shift kit
Sun Shell update
Input sprag
U-joint-frt (RR driveshaft)
U-joint rear (rear driveshaft)
MLPS-OEM

Is there anything else that can be checked that might cause tranny not to lock-up?Thanks, Michael