I was judt wondering if the modulator was adjustable within reason on a 200R4. Also, what is the purpose of the small opening on the intermediate servo...relief, or does it supply pressure to the secondary piston. I noticed that the super servo and mega servo do not have these openings.
Hi Dan. The 200-4R does not use a vacuum modulator. Or a convetional "kick-down". It uses a throttle valve that senses throttle position, by means of a cable that happens to be very similar to a kick-down cable. It even goes into the trans in the same location as a TH350 kickdown cable. It does control kick-down, BUT the BIG difference is, it changes the position of a pressure boost valve that puts higher fluid pressure on the clutch-packs and band, as the throttle is opened. More throttle = more pressure. If it is not properly adjusted the trans fluid pressure will not rise with throttle and the trans will soon melt-down. For adjustment instructions, look for info at www.transmissioncenter.com /or look at www.bowtieoverdrives.com They have detailed instructions that will help you get it adjusted properly. Shifts will crisp up, but rpm of shift is controlled by the govenor. Unfortionately GM put the gov. is inside the pan!!! This is adjusted by using different springs and weights. Both of the above websites can also get you info and parts to adjust your shift RPM at the govenor. As for the servo hole, it's probably a relief hole. Left unchecked the fluid pressure may give real hard part throttle shifts. What most of us look for is progressively harder shifts as speed and throttle increases. Smooth when the wife drives, and tire chirps when we do. The GN code BR or BQ trans should have a servo with the last two digits on the cover of 92 or 94. These servos give the shifts most of us look for. Hope this clears things up, Have fun!!!!