Rebuilding The 904 Torqueflite Transmission - Three Speeds Forward

Our late-model A999 was already equipped with the desirable five-clutch, high-gear/reverse drum. This is a worthwhile upgrade when building an earlier model 904 trans. More clutches equate to more holding power.

These five bushings were replaced: high-gear/reverse drum, front pump, front ring gear, extension housing, and pump stator support.

The High-gear/reverse clutch drum has a wave-loc snap ring (on right) that holds the clutches in place. We replaced it with a flat snap ring that will improve the second- to third-gear shift. The wave snap ring was designed to soften the shift on passenger cars. We like our trannies to bark the tires on upshifts. A wave-loc snap ring is also used on the input drum as it softens the engagement into gear from park. You will want to leave that one alone.

The original plastic accumulator was replaced with an aluminum piece from an earlier 904 (727s use the same part). Not only is the aluminum unit stronger, it will also provide a better seal than the plastic unit.

Transgo's instructions show you what modifications need to be made to the valvebody. These two holes were drilled in the separator plate. Transgo even provides the correct drill-bits.

A new manual valve is provided with the Transgo kit. The manual valve directs the trans into gear when you move the selector (shifter). The OE manual valve doesn't allow the transmission to pump oil while in Park, making it necessary to check our trans fluid level in Neutral. Transgo's replacement manual valve makes the transmission pump oil even while in Park. This is a particularly important feature that would benefit any vehicle that spends a good deal of time idling, e.g., emergency and delivery vehicles, because lube will continually flow through the transmission. Now we can check our fluid level in Park.

The band on the left is a standard 904 band and is 1.3-inches wide. The most desirable band is the one that came standard in 904s behind 360 engines and were 1.75-inches wide. While our A999 came equipped with the wider band, we could not get a replacement in time, so we went with the next best option, an A500 overdrive band (right) that is 1.6 inches in width. Will it hold up to the punishment of our Stealth Bomber? Only time will tell.

Here, our buddy and tranny man Neil Kaukola of Bob's Transmission in Simi Valley, California, hoists our refurbished bullet back under the Diplomat.

When reinstalling the front pump, torque the six bolts between 18 and 20 lb-ft of torque.

The trans pan on the right is the original shallow unit, but we opted for the deep unit on the left. The deeper pan is from an A500 and provides increased fluid capacity.