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After numerous posts, inquiries, web searches, I have finally resolved the leaking seal issue on my '97 Z3 ZF transmission. In a nut-shell, I picked up this car as a project and notice the leaking ATF after I got it on the road. I pulled the transmission and replaced the seal 3 different times with no success. Every time a new seal went it, it was leaking within 10 miles. Decided to pull for the last time and swap with a different transmission. While I was looking at my ZF sitting on the bench, I noticed some ATF dripping down from behind the main bearing at approximately 10:00 position. I angled the transmission at a 45 degree angle and turned it around. Once that spot (10:00) was under the ATF level, fluid started flowing out. The problem is that the ATF was dripping behind the bearing and filling up the chamber between the bearing and the input shaft seal. From there, it was dripping out.
The solution is as follows. First, I drained out the ATF, set the transmission vertically (input shaft upward) and let sit for 24 hours. I then took a scruffy-pad and worked the input shaft to insure there were no burrs or deposits that would prevent a clean seal between the input shaft and the seal. The next day I took Q-tips with Acetone and cleaned off the bearing surface and housing area - idea was to get any ATF fluid cleaned up and have a clean surface. I then picked up some Permatex RTV Gasket Maker for Gear Oil. This comes in a green tube and is silver in color. I applied a heavy bead of RTV all the way around the bearing and used my finger to smooth out and force the RTV into the recess between the bearing and the housing. I let this completely dry for 48 hours. Lastly, I applied a new seal, but decided to skip the BMW OEM and found a cross referenced SKF brand Oil Seal (#13972) that is metal and made in the good old USA.
Filled up the transmission with ATF, installed and I have put on over 250 miles without a drop of ATF coming out. I pass this on as I believe the key to this solution is the prevention any ATF to get between the bearing and the input shaft seal.
Thanks to all who responded to my previous posts with their tips and suggestions. Hope this one helps someone out there.
Mark
After numerous posts, inquiries, web searches, I have finally resolved the leaking seal issue on my '97 Z3 ZF transmission. In a nut-shell, I picked up this car as a project and notice the leaking ATF after I got it on the road. I pulled the transmission and replaced the seal 3 different times with no success. Every time a new seal went it, it was leaking within 10 miles. Decided to pull for the last time and swap with a different transmission. While I was looking at my ZF sitting on the bench, I noticed some ATF dripping down from behind the main bearing at approximately 10:00 position. I angled the transmission at a 45 degree angle and turned it around. Once that spot (10:00) was under the ATF level, fluid started flowing out. The problem is that the ATF was dripping behind the bearing and filling up the chamber between the bearing and the input shaft seal. From there, it was dripping out.
The solution is as follows. First, I drained out the ATF, set the transmission vertically (input shaft upward) and let sit for 24 hours. I then took a scruffy-pad and worked the input shaft to insure there were no burrs or deposits that would prevent a clean seal between the input shaft and the seal. The next day I took Q-tips with Acetone and cleaned off the bearing surface and housing area - idea was to get any ATF fluid cleaned up and have a clean surface. I then picked up some Permatex RTV Gasket Maker for Gear Oil. This comes in a green tube and is silver in color. I applied a heavy bead of RTV all the way around the bearing and used my finger to smooth out and force the RTV into the recess between the bearing and the housing. I let this completely dry for 48 hours. Lastly, I applied a new seal, but decided to skip the BMW OEM and found a cross referenced SKF brand Oil Seal (#13972) that is metal and made in the good old USA.
Filled up the transmission with ATF, installed and I have put on over 250 miles without a drop of ATF coming out. I pass this on as I believe the key to this solution is the prevention any ATF to get between the bearing and the input shaft seal.
Thanks to all who responded to my previous posts with their tips and suggestions. Hope this one helps someone out there.
Mark
Solution for 1997 Z3 ZF-S5D-310-Z front seal keeps leaking
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