It is not unusual for a 2000-2004 Honda or Acura vehicle using a 5 speed 3 shaft style automatic transmission to come in to the shop with the third clutches destroyed (figure 1). Many times rotational damage of the piston, return spring and spring retainer accompanies the third clutch burn out (figures 2, 3 and 4).
The main shaft, counter shaft and secondary shafts are each supported by their own bearings secured in the main case cover (figure 5). Overtime, vibration combined with torque causes these bearings to wear into the case allowing for unwanted shaft side play. Stationary hydraulic feed pipes in the end cover that fit into these shafts run hard against the rotating bushings inside the shafts (figure 6). The wear caused by shaft side play not only damages feed pipe sealing capabilities dropping clutch pressure (4th & 5th clutch main shaft, 3rd clutch counter shaft, 2nd clutch secondary shaft), damage can also extend to the sealing rings on the front of the main shaft. When this happens to the main shaft, the rings to cut into the regulator valve body compromising converter pressure. In fact one symptom this causes that rebuilder
It is understandable how the third clutch can burn out due to a pressure loss caused by worn feed pipe bushings, but the rotational damage? Jesse Zacarias of Elec-Tran discovered a computer strategy which briefly pulses the third clutches on and off during a forced 4-2 downshift. Factory manuals show this clutch being pulsed on and off during an engagement from Park to Drive without mentioning the 4-2 shift strategy. The purpose of this brief pulse of the clutch is to assist in a smooth shift transition. After 80k miles or so when shaft alignment begins to be compromised, this forced 4-2 downshift becomes a problem. The third clutches are being applied (albeit briefly) during high rpm conditions with less pressure control resulting in clutch burn out with rotational damage.
