6 Speed Transmission Leak

[NSXGB]

I have a minor leak from my 6 speed transmission. Originally I thought it was from the solenoid and have bought a new O ring to install. However, before I started I noticed that there is a concentration of fluid around the bolt beneath (bolt is centre top of picture) and wondered if that could be the source of the leak and not the solenoid.
Hard to see front the parts diagram, but I think that bolt holds a spring and steel ball. Not sure if it could be a source of a leak as well?

Has anyone hadxa similar leak or offer advice please?

 

[Old Guy]

First off, no direct experience since I have never had a leak.

That does look like one of the ball / spring retaining bolts. The thing is that those bolts have a fairly long fine pitch thread

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In the service manual Honda does refer to it as a sealing bolt. Given the length of the thread and the fact that the oil pressures are not huge I would not expect a leak. The service manual says the bolt threads are to be coated with liquid gasket so if it has never been disturbed I would be surprised that it would leak. But, never say never.

I would vote for the oil pump strainer cover (that cover retained by a bolt in your photo) which is sealed with an O ring as a more likely candidate to leak, particularly if the strainer was removed and cleaned as part of a transmission oil change.

 

[NSXGB]

Thanks OG.
The box was apart to install the 'R' final drive and input shaft, so possibly not resealed.
It may be worth me doing both the bolt and solenoid seal, to save potentially draining the MTF twice. As long as it does not cause issues removing the bolt - hoping it's not a bolt that should only be removed with transmission apart!
I have a spare strainer seal too, so for what it's worth I could do them all.

 

[Kaz-kzukNA1]

Super busy week and weekend so just a quick one.

Hard to tell from the photo.
Same mechanism used on 5MT as well.
Not something start leaking with age although now you mentioned that the gbox was opened.

Did you open it recently and found the seepage soon after?
If not, very unlikely from there.

Because it’s hard to tell from the photo, I would first remove the airbox and look for any trace of oil at the top forward section of the gbox.
Due to the air flow while driving, quite often, you would see oil seepage from distant place landing at the bottom side of the gbox.

Pay attention around the breather tube.
Also, around CL slave cyl and the hose.

Then, clean the area top to bottom, leave overnight and inspect again to see whether it’s actually leaking from that sealing bolt or not.

By the way, did you drive your NSX at extreme high speed continuously or on track?
I’m talking about the speed level of autobahn continuous high speed cruising and not like the 70mph motorway/freeway cruising for 2hrs or so.

Kaz

 

[NSXGB]

Thanks Kaz.

Leak has been there for quite a while but very minor, so has not been addressed as a priority.
Not been driving the car much lately either.
I've not noticed anything seeping higher than the solenoid. Collection of MTF inside the solenoid boot though.
All, dry around the clutch slave and hose which were replaced a few years back.
No high speed shenanigans for a few years now!

I'll clean area and leave overnight.

 

[NSXGB]

Update...after cleaning said bolt and leaving for a few days, it is indeed leaking.
Is it just a matter of undoing, cleaning and torqing to spec, with a little Honda Bond on the threads?
MTF will obviously be drained as part of the procedure.

 

[Honcho]

Update...after cleaning said bolt and leaving for a few days, it is indeed leaking.
Is it just a matter of undoing, cleaning and torqing to spec, with a little Honda Bond on the threads?
MTF will obviously be drained as part of the procedure.

Yes, but there is a ball bearing and spring behind the bolt that you must take care not to lose. Also, make sure to clean the internal threads too- not just the bolt- or you will have another leak. Use Hondabond HT.

 

[NSXGB]

Many thanks.
Page 13-52 on the workshop manual for future reference.

 

[NSXGB]

Bolt removed. Glad I had to remove it. God only knows why someone had ground down the end of the bolt??? Any ideas?
Luckily I have a spare gearbox and switched bolts to get the job all finished today.

 

[Honcho]

Bolt removed. Glad I had to remove it. God only knows why someone had ground down the end of the bolt??? Any ideas? View attachment 182018View attachment 182019
Luckily I have a spare gearbox and switched bolts to get the job all finished today.

Yikes. What a hack job!

It may be because the bolts are different lengths. Or rather, one of them (on the reverse selector shaft) is a different size than the others used on the main selector shafts. Whoever was in there last time may have lost the short bolt and used the longer one? Looking at the end of that grind job, I hope the magnet grabbed any bits of metal that broke off... :

 

[Old Guy]

That is truly bizarre. If it was a case of the unthreaded extension on the bolt being too long and bottoming out on something, why not just grind some off the very end rather than create that truly strange taper? It almost looks to me like they were having trouble getting the thread started and created a home made version of a tapered thread to help center the bolt in the threads.

 

[Kaz-kzukNA1]

I do hope it’s done by human error and not something internally ground off that bolt.
The photo just looked so strange with taper and even chipped off….

There are 2 types of sealing bolt in use but the other one is in different size and even the spring and the ball are different that can’t be mistaken with the one in your photo.

I’ve seen old gasket, washer, o-ring left in place before installing the new one on the engine.
I hope no extra parts such as another ball stuck above in that hole.
Don’t even know it can be done though….

Kaz

 

[NSXGB]

Certainly worrying, but transmission has been in the car about 8 years and seems fine...
I can't see anything internal grinding it down, not physically possible IMHO.