Causes of the VW O99 transmission, to stall the engine when slowing to a stop. Many readers have asked what causes the Volkswagon, particularly the O99 transmission, to stall the engine when slowing to a stop. This problem is an everyday occurrence in several VW type converters.
The problem usually occurs because of a worn TCC boost valve. Either the valve or sleeve are worn enough to prevent the correct stroke of the CC apply valve to the off position. Many rebuilders of the transmissions do not have the opportunity to test-drive the vehicle before repair. We suggest always replacing the TCC boost valve with the proper repair kit on all VW transmissions with excess of 50,000 miles.
This problem is commonly blamed on the torque converter after rebuild. Most likely the torque converter is not the catalyst for the problem itself so suggest to the customer that the valve body should be modified first before the converter is blamed.
Also, a two ounce bottle of Valve Protector should be added to every VW or ZF transmission. Valve Protector is one of Midco Lubricants’s newest products, and it will help prevent future wear on aluminum spool valves. This Valve Protector is only available through Midco Lubricants or one of its distributors. For more information, or to order this product, call 800-554-2668.