Transmission Leaks

There are several possible areas for the transmission to leak lubricant. Note the highest level of lubricant wetting on the case. What often appears to be a rear seal leak may actually be a vent or shift boot leak. If the transmission is extremely dirty it should first be cleaned and then road tested to ensure you can locate the source of the leak.

NOTE: A CLOGGED VENT MAY CAUSE A PRESSURE BUILDUP IN THE TRANSMISSION RESULTING IN FLUID BEING BLOWN PAST THE TRANSMISSION SEALS AND GASKETS. THE VENT MUST BE FREE OF DIRT AND THE RELIEF SPRING AND CAP OPERATES FREELY.

^ Transmission vent. Leakage at the vent may indicate an overfill condition or wrong lubricant. The vent is press fitted into the extension housing. It must be tight and seated. The vent must be free of dirt and the relief spring and cap operate freely.


^ Input shaft seal and gasket (front bearing retainer). Leakage in this area will appear in the clutch housing. A gasket leak will run down the transmission face. A seal leak will run through the release bearing support tube and leak on the clutch cover and disc.

^ Countershaft front bearing cup 0-ring. Leakage will appear in the clutch housing and run down the transmission face.

^ Speedometer pinion. Leakage at the pinion area may be caused by a loose retainer clamp, damaged 0-ring or speedometer cable seal.

^ Extension housing seal (rear seal). Leakage at the seal may be caused by scratches, nicks, burrs, or roughness on the propeller shaft yoke. The yoke must be replaced if the surface the seal runs on is damaged. Excessive propeller shaft runout may also result in leakage at the seal.

^ Shift boot, transmission access cover, case, extension housing. The source of the leakage in these areas may be hard to find. The transmission should be cleaned and vehicle road tested so that the source of the leak can be pin pointed. Possible causes for leakage in these areas include, cut or torn boot, loose bolts, poor RTV sealing, porous casting, scratches, nicks, burrs at the mating surfaces.