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Discussion Starter · #1 ·
I noticed an unusual issue today. While parked and waiting in my car with the windows down I noticed the distinctive gear lube smell. Got home and found there's a small area wet under the transmission. The weird part is that none of the seals look wet. The area seems focused around where the transmission mounts to the center member. The wettest spot (and a drip accumulating) was at the end of the long bolt that goes thru the tube. The tube is also wet along its entire length. Pretty sure it's this one in the assembly:



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Some photos of the wet areas.

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I'm guessing the factory drilled the hole too deep and there's a hole into the transmission behind this bolt. The best solution I can think of right now is to pull it apart, clean well with some brake cleaner, then douse everything in RTV during assembly and hope that seals it. Does anyone have a better idea to fix this that wouldn't require pulling the whole transmission?
 

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Your passenger side output seal is slightly above that. There is a possibility that the trans has a bad cast but I doubt it as it would have been noticed a long time ago. I would assume that the output seal is bad and the car could have been parked at an angle to emphasize the leak.
 
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Discussion Starter · #3 ·
Your passenger side output seal is slightly above that. There is a possibility that the trans has a bad cast but I doubt it as it would have been noticed a long time ago. I would assume that the output seal is bad and the car could have been parked at an angle to emphasize the leak.
I was expecting the same thing, but it's dry around the output seal. Totally baffled me, took over an hour looking around before I reached my conclusion.

I forgot to mention, when I previously had to take this apart to replace the upper oil pan seal (that I hadn't bothered to replace for years because it wasn't leaking heavily) I noticed that there was some transmission fluid at the end of that long bolt. I didn't think much of it at the time, but now I'm wondering if there had been a leak for a long time, and my removal and replacement of that bolt has allowed it to leak more than it used to.
 

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How did you support the engine/trans with the cross-member out?
 

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Discussion Starter · #5 ·
How did you support the engine/trans with the cross-member out?
Engine hoist with slingers and a jack stand under the transmission for backup. Engine was lifted slightly before unbolting and removing the center member. Everything went back together easily without any need to move things around to get the bolts to align.
 

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Discussion Starter · #6 ·
Once I make some room in my garage I'm going to get the exhaust and center member out of the way and run a borescope in the bolt holes. Once those parts are out of the way if I discover something different then my plan will have to change. I'll post some photos here once I get to that (maybe by next weekend).
 

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Discussion Starter · #7 ·
Well I took it apart this weekend and still not 100% sure where the leak is. It does look like the output shaft seal has leaked, but it doesn't look anywhere as damp as where I'm seeing wet mounting bolts. Could the dirt be hiding it that well?
When I removed the bottom bolt I could see oil dripping out of the tube, but the borescope didn't show anything interesting. What I didn't expect is that the upper mount bolt is also covered with transmission oil. The threads on this one seem even more coated than the bottom ones. Nothing is wet above this point, no oily dirt or anything. Could the output shaft be throwing it up this high yet somehow not get everything else covered?

Bottom bolt dripping as I remove it.
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Output seal. Some built up oily dirt, but didn't look wet.
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All the holes look like this, there goes that theory. It was probably a weird one anyway.
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Threads of upper mount bolt when removed.
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Oil all along this side of the mount. The top hole is above the output shaft seal. How does this happen???
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I went ahead and cleaned everything off and put it back together. The transmission wasn't full (no surprise) and took about 1/3qt to top it off again. I'll drive it for a weak or two and hopefully reach a better conclusion.
 

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Looking at the holes it looks like they have been helicoiled and the bolt looks like it has had the end turned down to fit a smaller hole diameter.
Has there been any work done on the transmission mount which might have stripped the original threads ?
 

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All of that debris on the output seal tells me it has been leaking. If the seal is/was bad, any excess oil that expanded due to heat would have seeped out until it got to a normal fluid level. I think your oil level in the tranny was a little high and the results is what you have now, a phantom leak with no source.

Hit the out put with some brake cleaners and wipe it down.
 

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Discussion Starter · #10 ·
Looking at the holes it looks like they have been helicoiled and the bolt looks like it has had the end turned down to fit a smaller hole diameter.
Has there been any work done on the transmission mount which might have stripped the original threads ?
I was wondering about that myself. Before I did my own repair work, the Nissan dealership told me there was an output seal leak and I paid them to replace it. If that's not stock then they must have stripped them and repaired it. I can't think of any other work someone else would have done that would require removing the transmission mount. I started doing my own work in '07 when after routine service I found they had overfilled the oil by about 3/4 quart.
 

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Discussion Starter · #11 ·
All of that debris on the output seal tells me it has been leaking. If the seal is/was bad, any excess oil that expanded due to heat would have seeped out until it got to a normal fluid level. I think your oil level in the tranny was a little high and the results is what you have now, a phantom leak with no source.

Hit the out put with some brake cleaners and wipe it down.
It's clean now. The fluid level was definitely lower than the service manual "full" level (yes I checked it with the vehicle level). Going to run it a week or two (couple 100 miles) and then take another look. The best bet is still the seal, just really confused how it ends up in the upper bolt hole. At least I know it's not leaking out quickly enough that it will be running dry in a short period.
 

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Its a low point, Fluid seeped through the threads and sat there due to surface tension as it filled that area and into the mount, doesn't surprise me.

At least they fixed the threads instead of just throwinng it in and/or RTVing it and calling it a day.
 
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