Transmission Seal

Inspect/Replace

When inspecting the transmission seal, you will need to look at three seals: the front pump seal, which is located between the torque converter and the front pump; the rear seal, which is located on the extension housing (also called the tailshaft); and the shift lever seal, which is located on the shift lever on the side of the transmission. Inspect all three seals for cracks, tears and fluid leaks. If you find fluid leaks, the seal must be replaced.

To inspect the front pump seal:

  • You'll need to remove the access cover from the housing.
  • Some housings don't have an access cover. In this case, disconnect the battery ground cable and remove the starter.
  • If you see red transmission fluid, the front pump seal is leaking.
  • If you see oil or a film on the front side of the flexplate, the leak isn't from the front pump seal. An oil leak from the engine crankshaft seal could be the cause.

To inspect the rear oil seal:

  • Look for signs of leakage at the rear of the extension housing.
  • Fluid leaks from the seal of the extension housing can be corrected with the transmission in the car.
  • The leaks can be coming from a faulty seal or often, the cause for leakage is a worn extension housing bushing, which supports the sliding yoke of the driveshaft.
  • When the driveshaft is installed, the clearance between the sliding yoke and the bushing should be minimal. If the clearance is satisfactory, a new oil seal will correct the leak.
  • If the clearance is excessive, the repair requires that a new seal and a new bushing be installed.
  • If the seal is faulty, the transmission vent should be checked for blockage.

To inspect the shift lever seal:

  • Look for leaks on the shift lever.
  • It is sometimes necessary to remove the pan and valve body to be able to remove the shift lever shaft.

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