1962 Corvette: Service Bulletin: Aluminum Powerglide Valve Body, Governor and Rear Pump Changes
Subject: Aluminum Powerglide Valve Body, Governor and Rear Pump Changes
Model and Year: 1962 Chevy II, "327" Engine Passenger Car and Corvette Models
Source: Chevrolet Technical Service Bulletin
Bulletin No: DR #525
Date: March 13, 1962
TO: ALL CHEVROLET DEALERS
On November 30, 1961, a revised valve body assembly entered aluminum Powerglide transmission production, and revised governor and rear pump became effective in production on December 28, 1961.
The valve body change was incorporated to relocate the high clutch exhaust to the top of the valve body to eliminate the possibility of partial high clutch apply during reverse overspeed such as occurs when rocking the vehicle in mud or snow. On valve bodies built prior to November 30, the high clutch exhaust could pull oil back into the clutch during reverse overspeed due to the centrifugal pumping action of the clutch during this condition.
Because of the valve body design change, service personnel must now determine whether the valve body is of the first or second design before ordering any replacement assemblies or parts. Although the later design valve body is installed in all transmissions since transmission serial number "B1130D", transmissions with earlier serial numbers may have had the later design valve body installed in Service. Therefore, it is recommended that the valve body, or component part, be positively identified as described in the applicable identification column of the "Valve Body Service Parts" chart on page 2 of this bulletin before installing replacement parts.
GOVERNOR AND REAR PUMP
The governor and rear pump revision, which entered production effective with transmission serial number "B1228D", was adopted to eliminate the possibility of delayed upshifts due to governor pressure leaking past the rear pump bushing. This was accomplished by reversing the positions of "Governor out" and rear pump oil pressure passages in the governor. As shown in Figure 2, "Governor out" pressure is relocated between the two rings and rear pump pressure to the governor is now adjacent to the rear pump bushing. With this arrangement, any slight leakage at the bushing would have no appreciable effect on rear pump pressure and thus no adverse effect on governor pressure.