Transmission Pan Gasket Leaks

Do you have a transmission fluid leak coming from the transmission pan gasket area after a new transmission fluid, pan gasket and filter installation? Transmission pan gaskets typically never fail. One of the following scenarios is likely the root cause. This article will help troubleshoot a transmission fluid leak coming from the pan gasket. Following the information provided below during your new transmission pan gasket installation should ensure that you do not experience a premature transmission pan gasket leak. 

Thoroughly Cleaned Transmission Pan Gasket Mating Surfaces

The transmission pan gasket mating surfaces should be thoroughly cleaned and cleansed, free from corrosion, road debris, oils, solvents, and fluids allowing for a perfect dry fit and seal. When done improperly, the gasket area may weep or leak transmission fluid.

Transmission Pan Gasket Alignment

If the gasket has not been properly aligned during installation it can begin to roll off its intended gasket sealing/mating surface causing transmission fluid to weep or leak. If it is determined that this is the case, the transmission fluid should be drained from the transmission, the transmission pan should be removed, allowing for a thorough cleaning and cleansing of all gasket mating surfaces (as outlined above). Note that paper gaskets are typically not reusable.

Factory Torqued Transmission Pan Mounting Bolts

If the factory intended transmission torque specifications are not confirmed and are over torqued, this can cause an uneven load to the transmission pan gasket and subsequent leak. Rubber style pan gaskets will bulge or role off the intended gasket sealing mating surfaces causing a transmission pan gasket weep or leak. Over torquing or under torquing a paper or metal gasket can result in ether too much or too little pressure, allowing the transmission pan to unevenly compress the gasket, resulting in an improper seal.

Transmission Pan Mounting Bolt Torquing Sequence

Most gasket mounting requires a particular bolt torquing sequence. Depending on the style of transmission and the procedures set out by the manufacturer, the transmission pan mounting bolts have an order of how they should be tightened. This sequenced order of tightening the bolts allows the gasket to be evenly squeezed ensuring a proper seal. When done improperly this can cause the gasket to weep or leak.

Paper Style Transmission Pan Gasket

Confirm that the paper gasket has no kinks or creases. If a paper gasket is kinked or creased, this will cause an imperfect seal and can give the transmission fluid a small channel to weep or leak through.

Rubber Style Transmission Pan Gasket

New fully rubber transmission pan gaskets rarely ever leak prematurely. However, old and aged gaskets that have experienced thousands of heat cycles can cause the rubber to harden and shrink resulting in a distorted seal and subsequent leak.

Metal Style with Incorporated Rubber Transmission Pan Gasket

Confirm that the gasket has no kinks or creases. If it has been kinked or creased, this will cause an imperfect seal due to an uneven metal and rubber mating surface, resulting in a small channel to weep or leak through.

Use Caution When Unpackaging Transmission Pan Gasket

While unpackaging your new transmission pan gasket you will need to confirm that you didn’t damage any part of the gasket with a razor blade knife or kink the gasket. 

Even new transmission pan gaskets can leak if the above procedures and examinations weren't followed thoroughly. When performing your transmission filter and fluid change, take the extra time needed to do it right and prevent any premature transmission gasket leak issues.