Hi all,
I put a TH700 in my Cadillac a few years ago and had some similar issues before I drove it.
The TV "valve" will be loose in the bore, if you don't have the cable connected at the carb or adjusted tight enough, there will be "freeplay" between the end of the valve and the lever which pushes it.
Once adjusted correctly there wont be any free play.
There is a very specific way that the cable and bracket needs to be set on the carb to work.
Most manufacturers have the correct pin and geometry in the carb specs.
If you don't set it right you will have late shifts, low TV pressure which may cause burned clutches if pushed hard.
As stated, later model trans had a "safety" in them so if the cable snapped it gave you full TV pressure, this would give very harsh, late shifts, but a safe pressure for the clutches.
once you have the correct brackets and mounts for the cable on the carb, you can get a pretty good setting by adjusting the cable until it is TIGHT with throttle at WOT, so you really cant pull any slack in the TV cable, at closed throttle, there will be some tension on the cable, this is from the springs in the TV valve.
Don't try and check pressure before you have the cable hooked up and adjusted, you are wasting your time.
once you have the TV cable adjusted, then you can drive it, you may need to adjust the GOV, as the heavy truck will have different shift points than a sedan.
http://www.tvmadeez.com/article/