Classic/Antique Car Repair: Powerglide Transmission Vacuum Modulator adjustment., transmission vacuum modulator, 1964 chevy nova

Question
Hi,
 I need your help.  My wife and I own a 1964 Chevy Nova, with a 194 C.I. 6 Cyl. engine.  We recently had the engine and transmission (aluminum Powerglide) rebuilt and have re-installed them at home.  A new Vacuum Modulator was installed on the transmission. I have attempted to adjust the modulator, but have not noticed any change when doing so.  Does the adjusting screw get turned "clockwise" or "counter-clockwise" and how many turns?  At what speed should the transmission upshift and downshift?  Just today, after having driven the vehicle for approx. 1,000 miles since the rebuild and my attempt at adjusting the Modulator, my wife claims to have noticed (it's her car)that when shifting into reverse it is "clunking" heavily. Is this an out of adjustment thing or a sign of something else?  Please reply ASAP, as my wife thinks she's done something wrong to the car and it would help ease our mines to know it's not so. Thanks in advance!
Steve and Maria

Answer
Steve;
     Well as far as the modulator , you might have to play with it till you find a spot that works for you , but when you say that it bangs in reverse ,, I do not think it is the modulator - I would look at the motor mounts , and the tranny mount and the drive shaft U-joints. the tranny is on a 6 cyld. it should not have that much psi. for it to cause much trouble , if it is not slipping .and the tranny should kick in around 30 / or so