Thanks Kawabuggy for posting on blocking the line bias valve. I don't know for sure what gen my 700R4 is. The car is an 87, the trans code is MXM, which isn't even an option for my car's year model. The valve body was obviously replaced in the overhaul 25K miles ago because it's brand new.
As it happens, everything worked out just about perfect. I finished the build and installed the unit this past Saturday and on two road tests I have been very pleased with it's behavior. The light throttle bang shift I used to have from 1-2 is gone. Now the light throttle shift is firm and solid but not harsh. The shift is progressively firmer with throttle pressure as it should be and above half throttle it is quick and confident. The 2-3 shift is the same, firm but pleasant at light throttle and firmer as the throttle is depressed further.
One thing I want to mention is the 3-2 and 2-1 shift with the Superior servo. I have not noticed any clunkiness in the shift. I just barely hear the servo clicking against the sealing piston(no cushion spring) but there is no unpleasant shift feel. Both shifts are quick and clean and I don't mind the click sound. It just adds character.
One thing though and a point of concern for anyone planning on overhauling their 700R4, I really wish now that I had replaced my rear planet. The gear teeth all looked good and the pinion gears and shafts were all solid. Still, as I assembled everything, I noticed what seemed like excessive gear lash between the rear sun and pinions. Now that the unit is back in, I hear the same noise Ive always heard since this unit was built 14 years ago as I wind up the motor in 1st and 2nd. I know now that it's the rear planet growling.
Even if it seems okay, replace this gear set when you're in there. Now I'm going to have to go back in. I'll wait til next winter and since I know everything else is solid, I can just go in quickly on a one day R&R at the shop and swap out the rear gear set. I'll save up and go with a 5 pinion AC Delco unit. I have heard that the aftermarket 5 pinions aren't worth bothering with.