Transmission output shaft seal

[83nissansunrader]

Hello,

 

I have completed an overhaul on the driveshaft, had it rebalanced, new slip yoke and installed a new output shaft seal.  However, I may still have a small leak at the output shaft.  When I installed the new seal I cleaned the opening and installed the new seal using a large socket.  What I did not do was apply a silicone to the outside of the seal.  
 

I noticed in a previous post Mike you mentioned to someone to coat the outside of the seal with silicone.  
 

what type of silicone if I were to reinstall a new seal.  
 

thanks 

[datzenmike]

The seal outer surface has a coating that seals it to the case, so if I said put a small amount of RTV on perhaps the transmission case was damaged or in bad shape. I've never done this but you could. 

 

Did you grease the seal lips or the spline before inserting it? Don't want the seal to be dry when it starts turning. 

 

Have you over filled the transmission oil? Takes only 2 liters of GL-80/90, or sitting level fill till it reaches the fill hole. NEVER overfill.

 

Is the vent clear of obstruction? As transmission heats up, and it gets very hot, expanding air inside has to be able to vent.

[83nissansunrader]

Thanks Mike.  I do have an update.  The oil is not leaking from the seal.  I just came from a drive around.  Quickly went under the truck and wiped the transmission tail clean.  Then I saw where the oil is coming.  It’s dripping from the section above the tail.   The oil will drip off that top section then down on the  output shaft flows around the output shaft and creates a drop right at the seal.  This is why I thought it was the seal. If I knew how to post a picture I would.  Looking at the tail, there is the output shaft.  Above that there is a cylinder like section that runs parallel to the output shaft.  This also the section where the stick shift is attached above it.  I have been filling the transmission with gl4 synchromesh from ac Delco.  Having a hard time sourcing anything else.  I had changed the oil not long ago and it takes 2 litres and then overflows.  So I can see over filling.  If you can tell me where or who sells gl4 89/90 let me know

[ggzilla]

1 hour ago, 83nissansunrader said:

it takes 2 litres and then overflows.  So I can see over filling.

Overflowing means it is too full, and will leak out when driving

 

Park the rig on a level surface, then remove the side plug. Let it totally run out of the hole, until no more drops, then put the plug in and tighten slightly

[83nissansunrader]

Thanks grailla,  however, I did fill the transmission from the side plug.  And filled it to the point where it was running out.  So I don’t think the transmission is over filled.  

[ggzilla]

sounds good. so the next thing to check is the breather. Any leaks from up high in the striking guide I think would be caused by pressure

 

 

striking rod guide

[datzenmike]

If it's that plug wash off with brake cleaner and rub some RTV around it. 

 

 

Could also be the return plug and the stopper pin just forward of it

 

Stopper pin Has a C clip holding it on.

 

[83nissansunrader]

So yes, this is exactly where I can see the oil dripping from when I’m stopped.  Looking at ggzilla’s picture, it seems to be coming from where the green arrow is located.  The end of the striking guide is open with a recessed plug like that has a flat “H” shaped insert.  I don’t have a smooth disk like button/plug on the end of the striking guide like in ggzilla’s picture.  The fact there is no plug, is that why it’s leaking?  

 

mike, the plug your are referring to in your picture is located where?  Is it on the other side of the tail section of your picture?  I went to Datsun1200.com and found a few pictures or references of that spring plug.  Is this the breather whole?

 

thank you both.  It would be amazing if I can solve this issue.  Especially when I have replaced or updated everything else.  

[83nissansunrader]

Just checked my Haynes owner workshop manual.  On page 159 picture 4.7 I can see the return spring plug.  I can see the return plug on my unit and should be able to access it.  

 

also looking at figure 7.6 on page 163 I see that the  striking  guide there is an oil seal - the striking rod and an expansion plug.  Clearly I do not have that plug on my the tail section.  I think what I’m seeing is the end of the striking rod, which explains the flat “H” shape I’m seeing.  So if the striking guide is leaking, is it because the oil seal in front of the striking rod is not sealing or is it because I don’t have the expansion plug

 

a reminder, this transmission was purchased last fall from High Gear in Memphis and brought to canada.  It was rebuilt by them.  Not sure if this oil seal in the striking rod would be the issue.   Similarly the return plug should be fine as this should have been cleaned when they rebuilt the unit.
 

mike, I know you are in canada.  Where do you buy gl4 80/90 transmission fluid?   And where can I buy that expansion cap?

Edited September 7, 2025 by 83nissansunrader

[datzenmike]

 

If that plug is missing then look no farther for the leak. It's called a welch plug and when installed and hammered in it's diameter expands and seals a hole. Measure in mm and order one or try NAPA for one off the shelf. I would clean with carburetor spray, rub a small amount of RTV around the sealing surface of the hole and hammer a new plug in.

 

 

[ggzilla]

NAPA in Ontario has it. For example:

Valvoline High Performance Gear Oil 80W90, 946 ml VAL 3032 | Product Details

Make sure it says "GL-4" on the bottle, as a GL-5 rating alone is not enough for the brass synchros in our older vehicles

 

3 hours ago, 83nissansunrader said:

Where do you buy gl4 80/90 transmission fluid?

 

[datzenmike]

GL-4 Delco oil is fine if you have it. GL-5 contains 50% more sulphur anti scuff additives and should be used in differentials and never in a transmission.

 

GL-4... 4% sulphur additives will not harm copper/brass allow transmission synchro rings.

GL-5... 6% or 50% more additives that break down over time and will be concentrated enough to harm brass transmission synchro rings.

[83nissansunrader]

yes I made sure to use the gl4!  Just hard to find the 80/90 but will look at Napa.
 

Hope this is the end of dealing with a leaky transmission.  All because of a 5$ plug!  
 

mind you my original slip yoke had to be replaced ans it was leaking at back end where the plug is located. And the balancing of the drive shaft made a huge difference in reducing the vibration.  So now once I get this little plug in I hope to good for 1000’s and 1000’s of miles. 
 

thank you both for helping me out with this.  It has been incredibly useful to have this support.

[ggzilla]

Just now, 83nissansunrader said:

will look at Napa.

Many NAPA stores don't carry it, but at least one in the region will. So ask them to order it for next-day pickup. NAPA is very quick to move whatever you want to the nearby store

[83nissansunrader]

yes I made sure to use the gl4!  Just hard to find the 80/90 but will look at Napa.
 

Hope this is the end of dealing with a leaky transmission.  All because of a 5$ plug!  
 

mind you my original slip yoke had to be replaced ans it was leaking at back end where the plug is located. And the balancing of the drive shaft made a huge difference in reducing the vibration.  So now once I get this little plug in I hope to good for 1000’s and 1000’s of miles. 
 

thank you both for helping me out with this.  It has been incredibly useful to have this support.

[83nissansunrader]

Sorry thought my previous post was entered but just noticed it was not.

 

Tried measuring the inner diameter of the whole and got an approximate measurement of 33 mm.  Sorry don’t have a digital capiler.  Should get one.  Went to napa, order three different sizes within the 33mm range.  However, they only sold them in imperial.  So bought a 1 3/16 , 1 1/4 and 1 5/16.  The 1 1/4 was a really close fit.  Lightly Cleaned the inner whole with a wire brush, then some brake clean and a lean towel.  Spread a small bead of rvt on the inner diameter, then set the plug by hand first and tapped lightly with a ball pin hammer and it snugged right in there.  WOW!!!!  I hope this is the final chapter on this issue.  I’ve spent way too much time lying underneath my camper than inside it.  Hopefully now with fall coming in it will be time to explore.  I’ll let it sit over night and fingers crossed.  

 

thanks again To both of you for your support, time and expertise.  
 

until my next problem

 

pierre