Powerglide Trans-Brake Solenoid 0.200 in Stroke

This is the TCI 749800 trans-brake solenoid for the GM Powerglide, the part that actually does the work when you mash the transbrake button on the starting line. It is a 0.200 inch stroke solenoid, which is the long-stroke version TCI specifies for their Powerglide trans-brake valve bodies. The short-stroke solenoids used on other GM units will bolt on and look right but will not shift the transbrake valve far enough, so the car either creeps or releases early.

On the bench it mounts to the trans-brake valve body with the solenoid body sealed to the plate and the pigtail routed out through the case connector or a bulkhead fitting, depending on how the transmission is wired. Energize it and it blocks the reverse circuit so the unit is in low and reverse at the same time, loading the converter against the brake. Cut power and the valve releases, the reverse apply dumps, and the car leaves. Because it holds full line pressure while you build boost or RPM, a tired solenoid is the usual reason a car will not hold at high line pressure or drops off the brake under load.

Part number 749800, manufacturer part number 749800. Fits GM Powerglide transmissions running a TCI trans-brake valve body. Unit weight is about 15.8 ounces. Replace it as a wear item if the car has been on the brake for several seasons or if you have raised line pressure since the solenoid went in.