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If there's a bit of a lurch after taking your foot off the brake without touching the gas then I'd say that's an idle surge being created by the IAC, basically an idle control system problem, not a trans problem. The IAC is quite possibly sticky when it's responding to changing conditions, including slight changes in engine load and/or intake system vacuum. When conditions aren't changing or once you're away from idle then everything will run fine.
1) Check for a related vacuum leak.
a) Apply the park brake firmly and watch the rpm needle carefully when you take your foot off the brake -the needle shouldn't flinch, otherwise a vacuum leak, carefully check for hidden spolits at the vacuum ports on the throttle boy and intake. A leaking cruise control cutout switch on the brake pedal is a distinct possibility as it's related to pedal use.
b) Verify there's no leak at the hose fitting on the brake booster and that the check valve is sealing. There's another thing that changes vacuum when you use the brakes.
3) Remove the IAC for a good cleaning -holding it upright, a good spray of WD-40 around the base of the valve, work it in by rotating the valve a number of times (by rapdily twisting the housing) then follow with a solvent or carb cleaner flush and shake it dry. For bonus points, use the OBD system to work in the WD-40 by exercising the IAC full travel a number of times. If the problem initially gets better and soon returns then the IAC may be worn.
4) Clean and thoroughly check adjustment of the throttle body and idle control system.
a) Check for a leak at the throttle shaft by spraying a little water around the bushing when idling -the idle shouldn't change.
b) Remove and clean the throttle body, especially the edge of the plate and throat around where the plate closes as well as the two small ports.
c) If anyone has recently touched the idle stop screw (or you can't remember the last time it was adjusted) then properly re-adjust it using the stop screw 1/4 turn method with the TPS loosened.
d) Check that the throttle plate isn't capable of binding in the throat. Sight through the throat towards a light to make sure the throttle plate is evenly centred in the throat when it's closed
e) Check TPS adjustment that the TPS clicks just as you open and close the throttle with a strip of heavy bond paper inserted at the stop screw as a spacer.
f) Replace the gasket if it's damaged.
g) Check adjustment of the linkage rod and throttle cable by making sure the TPS still clicks when a strip of #10 envelope is inserted as a spacer in the cable spindle stop.
h) For bonus points, use the OBD system to verify that the ECU is getting the click signal from the TPS.
5) Clean the PCV system, most especially the small hoses and flame trap element.
Anytime I've had occasional lurching such as you describe, a TB/IAC cleaning and a good highway run usually put it right.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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