U Van Shift Schedule
 

Here goes:

At 12% TPS (throttle position sensor) value:

1-2 shift will occur at ~13 mph
2-3 shift at ~ 20 mph
torque converter clutch apply in 3rd gear starts at ~ 23 mph
3-4 shift at ~ 40 mph
torque converter clutch apply can start at that same speed in 4th.

At 25% TPS the shift points are 20, 31 and 51 mph, respectively.

Also at 25% TPS the torque converter clutch applies can start at 34 mph in 3rd gear and 47 mph in 4th.

At 50% TPS 1-2 and 2-3 are at 30 and 52 mph. 3-4 won't happen at 50% TPS :) .

With the throttle closed, 4-3 happens at 36 mph and 3-2 at 18 mph.

This should give you something to chew on.