Car Care
Auto-Trans Rear Seal Replacement
Curing leaks at the driveshaft
Created by Tom MorrAutomatic transmissions are one of the least self-serviceable components on a vehicle. The complexity of these transmission's internal parts requires specialized knowledge to rebuild them. However, a few auto-trans woes can be cured at home.
One such problem is a leak where the driveshaft couples to the transmission on rear-drive cars and trucks. A puddle under this area and the associated fluid around the transmission's output shaft mean that the seal is likely bad. Armed with a few hand tools, the average mechanic can often fix the problem in less time than is required to deliver and pick up the vehicle from a repair shop.
Notes
> Consult a service manual for procedures specific to your vehicle.
> Park the vehicle with the front facing slightly downhill to minimize the amount of fluid that seeps out during seal replacement.
> Allow the vehicle to cool before working on it.
> After disconnecting the driveshaft, secure it out of the way with wire or other suitable restraint.
> The old seal might need to be severely disfigured in order to remove it. However, avoid gouging the transmission's output shaft and tailhousing.
> Verify that the replacement seal is the proper size before attempting to install it.
> After all components are reinstalled and the vehicle is lowered, move to level ground and check the transmission fluid level following the procedure in the owner's manual or service manual. Top off as necessary.
> Test-drive the vehicle. The leak should be fixed. If not, some other transmission and/or driveshaft component might be damaged.
Step 1
Raise and secure the vehicle on jackstands. Disconnect the rear driveshaft from the transmission. Unfastening the carrier bearing did the trick on this pickup truck.
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Step 2
Once the driveshaft's yoke is slid off of the transmission's output shaft, secure the driveshaft out of the way. Transmission fluid may escape from the transmission's tailhousing as the driveshaft is de-coupled.
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Step 3
Pry out the old seal with a specialized seal-puller or by using a long screwdriver, claws of a hammer or other suitable tool.
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Step 4
Clean and inspect the seal area of the transmission housing for any signs of damage.
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Step 6
Drive the seal into the housing until it fully seats. Use a seal-driver, large socket, pipe or other item that's the same diameter as the seal (such as this exhaust coupling) to pound the seal home with a hammer.
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Step 8
To button up the job, reinstall the driveshaft, secure all fasteners and check the fluid level. The leak should now be cured.
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