ZF 6HP26 rear wheel drive can be identified by the 10 digit STUECKL number stamped into the case. Some parts are interchangeable with the Ford 6R80.
With a factory input torque rating of 600nm (443 ft lbs), some internal upgrades are required before being coupled to a higher output capacity motor. Exedy FDF have available a hi capacity stage 2 friction & steel kit that is rated for 1,000 rear wheel horsepower. Developed in the USA for the 6R80, the large friction plates for the A B C D clutch are increased in capacity from 22 plates to 27, some 6HP26 turbo models will require an extra 2 frictions and steels to increase capacity from 24 to 29. The small friction pack for the E clutch is increased in capacity from 7 plates to 9.
One of the most common faults that occur with the 6HP26 when the Boost is turned up, is a broken input shaft, due to the transmission leaving the factory at close to its nominated input rating. The aftermarket has designed billet shafts to overcome this problem and handle hi input torque. Another high wear part is the rear stator bushing that supports the input shaft overdrive drum.
Apart from mechanical upgrades, hydraulic valve body and accumulator upgrades are a popular fix for these units. Accumulator failure is common and often overlooked. The following shows a new compared to a used and flattened accumulator that has lost the ability for effective hydraulic dampening. The Performance Accumulator shown corrects shift faults caused by a collapsed rubber.
Both Transgo and Sonnax offer valve body upgrade kits to resolve shift issues.
The valve body seperator plate uses bonded rubber beading rather than paper gaskets to seal and direct oil to the correct channel casting. The beading must be complete with no breakage or deformaty. The plates are coded and like for like must be used on replacement. Always replace the valve body tube seals the case block seal and harness sleeve.