I am pretty much done getting my 7th gen swap all put together except for this last on going transmission leak issue I want to solve. even though I get the seals from nissan it never seems to seal the transmission properly on the driver side axle. I have changed the seal 3 times in the past 2 years, part number 38342-81X00 from Nissan. I notice that whenever I've installed it the seal is pretty much able to be forced in by hand while the passenger side one fits real good and tight and takes a while.

anyone have any ideas?

I'm thinking of sealing that out bore with RTV and 70mm washer with the inner bore machined to 54mm to seal the seal's outer bore from the outside...

this is on an 02 with 6MT

 

When you take the old seal out you cant see any cuts or scoring on the metal of the transmission where the seal seats can you? I've seen transmissions with cuts in the metal there from where someone improperly removed the old seal and left a gouge, if that happens no matter what it'll keep leaking

 

the seal itself just isn't fitting tightly into the bore. the passenger side one fits super tight in the bore but on the driver side it popped in easily by hand.

 

so I went to Nissan and got another driver side axle seal for 6MT and the same thing happened. the seal fit in the bore so loose that i was able to fully insert it by hand. the passenger side one was really tight.

I ended up using a 2 1/8" (2.125") inner diameter washer and Ultra Gray RTV to seal the outer bore of the seal to the case. I'm going to give it a full 24 hours to cure before I fill the tranny and start up my 7th gen engine for the first time. I also still need a o ring for the power steering pump inlet. the one I got from Nissan is already leaking from just adding fluid. looked thinner than the brown o ring that came on the pump...

 

I had a prolonged axle seal leak as well....turns out, the billion different aftermarket CV axles I tried were apparently the wrong diameter on the sealing area. When I finally sourced a used OEM CV axle, my leak stopped 100%. I didn't think to measure the sealing OD on the OEM axle before I put it in, because really I was just trying to get rid of some vibration caused by the aftermarket CV axle - stopping the leak was an extra bonus. But all I can think is that the aftermarket CV axles just have a slightly smaller OD than the OEM one, allowing some fluid to get passed the seal. If you have aftermarket CV's, that may be one cause. I also know the manual vs. automatic CV axles on these cars are different, so triple check that you're getting the right part number seal for the manual transmission.

 

I keep a picture of my VIN plate in my phone for when I get parts from Nissan as well as the part numbers for the seals with which side is which.
the one for the passenger side fits real tightly into the transmission case but the one for the driver side goes in by hand. under regular use I was adding about half a quart a month. I also discovered that the 6MT and 7th gen CVT tranny uses the same seals. I helped a friend with a 7th gen change his axles and seals once.

 

If it fits loosely....something is wrong. Not sure how or why your transmission would ever be altered, but those part numbers both fit very tightly into the seal recesses in my transmission. I just use a socket that fits around the outer edge of the seal to tap it in, but it takes a while to coax it into place.

 

at some point , like 2 years ago, the OEM Nissan seals for the driver side just stopped fitting tightly into its bore. the transmission case wasn't modified...

 

With enough experience you just become RTV Man and tell it to go **** itself, b/c you're not dealing with its dumb ***.

 

I put 70 miles on the car so far since completing the swap and no leaks whatsoever. but I'm not sure I really like this 6 puck clutch though...