Remove and Replace Transmission Oil Seal

My transmission has been a bit incontinent, dribbling on the garage floor at some slow rate. Careful inspection showed the transmission fluid was coming from the left half-shaft flange. The oil seal need to be replaced. This note describes the procedure.

The oil seal is described as 45 x 65 x 10 which presumably are the dimensions in millimeters. It cost about $5. The Porsche part number is 999 113 058 50.

The job was done completed in a couple of hours at my slow speed.

You can do the work without removing the transmission from the car. Just jack it up remove the wheel and place on jack stands.

To get started, remove the half shaft from the differential. Only one end needs to be take off.

Note: I had a problem with the stretch bolt that holds on the flange. It was replaced because it would not take the required torque. See the last picture on this page.

	Clean up the flange which will be partially filled with grease from the CV-joint. Remove the inner snap ring on the inside of the flange. The stretch bolt that holds on the flange is covered with an aluminum plug shown in the picture after the snap ring has been removed. There is a 'hat' on the plug that is used to help slide the plug out of the flange with a pair of screw drivers prying against the side of the flange. It took me two tries because the plug got off-center so I had to tap it back in and start over.
	With the plug removed, we can remove the stretch bolt. In my case the bolt came off easily. (Probably too easily. I'll replace this bolt).
	Here are the flange parts cleaned up and ready to be assembled back on the transmission. The new oil seal is on the left. At the bottom are the aluminum plug with O-ring and the snap ring. The largest polished portion of the flange is sealed against transmission fluid by the new oil seal.
	The differential cover has been cleaned up a bit and is ready for the parts to be replaced. You can see the new oil seal, the snap ring and the aluminum plug the flange and the (defective) bolt and it's washer. The aluminum plug has an O-ring which prevents transmission fluid from encroaching into the CV joint. I did not have a replacement O-ring, but now that I know it is there, I can replace it.
	The new oil seal has been tapped into the differential cover. I just used a small machinists hammer and tried to hit only the side that stuck out the furthest. Reassemble in the reverse order. Torque the stretch bolt to the differential pinion shaft. Tap the aluminum plug back into place. I tapped on the back of a socket in order to apply event force across the plug. Don't forget to torque the half shaft stretch bolts to the recommended 33-36 foot-lbs.
	I replaced the original stretch bolt with a new one. I was skeptical of the 80 foot-lb value mentioned by the factory manual. Ismail Nuri sent me a note (thanks) that his manual says 33-36 foot-lbs just like the bolts on the half shafts. Those values are much more reasonable.

Last modified: Sat, 10 Mar 2001

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