Mendola Main Seal Leaking

Cookie

Cookie

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To give some history, running a 2d.  This has been pretty consistent over the last couple of seasons, after about 15 days of duning the main seal on the tranny start leaking.  Each time I pull the tranny out and send it to a reputable builder for a refresh.  Nothing is ever wrong in the tranny.   So now fast forward, I am on the third round of it leaking and I really don't want to pull everything out again, but will have to due to the oil build up on the clutch, so I have two questions:

What could be causing this?

and is it easy to change that seal while the tranny is still in the car?

 
Like Jeff said above, always check pilot bearing, and ensuring it the correct pilot bearing for your engine/trans combo. The is the #1 culprit to leaking input shaft seal conversations I have.

Digging deeper, there can be a surprising amount of mis-alignment between the dowels that line up the crank with the input shaft. This pulls the input shaft and can let oil past the seal. But I cannot say this is the cause. We have often used a special tool with an Albins bell housing to check this, and install offset dowels in the block to line everything up. Certainly not a quick/easy/cheap fix.

It should also be noted that 2D's have 2 input seals stacked on top of each other, it baffles me when this things leak, it really should never happen. I have posted mu opinion about starting engines and letting them sit to warm up before jumping in and rolling. With the input shaft sitting high in the case, there is no oil getting flung up to the input shaft/back of the seal until you start rolling the car. If the engine is running with the trans in neutral and clutch pedal up, the input shaft is turning in the trans. There is a possibility that the seals are getting hot with no oil splashing up to them, then hardening and cracking allowing oil to pass by. 

 
Sean@Weddle said:
Like Jeff said above, always check pilot bearing, and ensuring it the correct pilot bearing for your engine/trans combo. The is the #1 culprit to leaking input shaft seal conversations I have.

Digging deeper, there can be a surprising amount of mis-alignment between the dowels that line up the crank with the input shaft. This pulls the input shaft and can let oil past the seal. But I cannot say this is the cause. We have often used a special tool with an Albins bell housing to check this, and install offset dowels in the block to line everything up. Certainly not a quick/easy/cheap fix.

It should also be noted that 2D's have 2 input seals stacked on top of each other, it baffles me when this things leak, it really should never happen. I have posted mu opinion about starting engines and letting them sit to warm up before jumping in and rolling. With the input shaft sitting high in the case, there is no oil getting flung up to the input shaft/back of the seal until you start rolling the car. If the engine is running with the trans in neutral and clutch pedal up, the input shaft is turning in the trans. There is a possibility that the seals are getting hot with no oil splashing up to them, then hardening and cracking allowing oil to pass by. 
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Isn’t there some oil flowing down the input shaft? If it’s VW style design, the shift forks are on the output shaft, so the gears themselves are always spinning, no?

 
Pilot bearing is the one inside the tranny?  If it is, I would assume it gets changed on every refresh, along with the Throwout bearing.

 
Cookie said:
Pilot bearing is the one inside the tranny?  If it is, I would assume it gets changed on every refresh, along with the Throwout bearing.
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It's behind the clutch. Have to remove that to get to the pilot bearing. And they aren't fun to remove either.

 
L.R.S. said:
It's behind the clutch. Have to remove that to get to the pilot bearing. And they aren't fun to remove either.
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Nope.  Highly recommend a blind bearing puller kit.  @Cookie I have one you're more than welcome to borrow if you want.  

 
no, the pilot bearing is the bearing (or bushing) that is in the end of crank or flywheel

the VW shaft seal never leaked.  the issue I see is with real estate issues when the g50 shaft came out.  the OD of the 2 seals are the same but the ID is way bigger on the G50 seals, this leave very little available "flexing" of the seal.  the G50 seal is mostly ridged with a very small lip (see pics whereas the vw seal had lots of flexibility).

so they stacked two seals but they still have a small ridged lip.  There is also flexing of the input shaft, even with the G50 shaft!  cant really go bigger diameter very easily as the bellhosing would need to be opened up more.

the tranny vent must absolutely have zero back pressure.  the oil seal leak is so common some tranny shops will tell you to run the oil level lower than the fill plug too 

IMG_1306.JPG

 
John@Outfront said:
the tranny vent must absolutely have zero back pressure.  the oil seal leak is so common some tranny shops will tell you to run the oil level lower than the fill plug too 

View attachment 91848
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That is a coincidence, I brought up to the tranny builder as well about venting.  He changed it out from the hose that routes up to a mesh type of vent that is right on the tranny.  The mesh is always dirty with sand.  I was also thinking this as a problem because the vent looks to get clog and that this would cause backpressure and push oil out the seals.

I wish I had pics to show the mesh vent, I can't seem to find it on the internet as well.  But it sits only a 1/4' off the tranny and it is a bronze mesh.

 
Cookie said:
That is a coincidence, I brought up to the tranny builder as well about venting.  He changed it out from the hose that routes up to a mesh type of vent that is right on the tranny.  The mesh is always dirty with sand.  I was also thinking this as a problem because the vent looks to get clog and that this would cause backpressure and push oil out the seals.

I wish I had pics to show the mesh vent, I can't seem to find it on the internet as well.  But it sits only a 1/4' off the tranny and it is a bronze mesh.
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it absolutley can not be a paper mesh (like the vw fuel filter)  thats your issue!

 
Rockwood said:
Isn’t there some oil flowing down the input shaft? If it’s VW style design, the shift forks are on the output shaft, so the gears themselves are always spinning, no?
Click to expand...
Yes, 1st and 2nd gears are spinning with the engine in neutral when the clutch pedal is up. But this is in a different oil chamber, so the oil doesn't easily migrate along the input shaft, especially in a car where the trans has a slight downward angle, then the oil goes towards the front of the trans and away from the bell housing. 

John@Outfront said:
no, the pilot bearing is the bearing (or bushing) that is in the end of crank or flywheel

the VW shaft seal never leaked.  the issue I see is with real estate issues when the g50 shaft came out.  the OD of the 2 seals are the same but the ID is way bigger on the G50 seals, this leave very little available "flexing" of the seal.  the G50 seal is mostly ridged with a very small lip (see pics whereas the vw seal had lots of flexibility).

so they stacked two seals but they still have a small ridged lip.  There is also flexing of the input shaft, even with the G50 shaft!  cant really go bigger diameter very easily as the bellhosing would need to be opened up more.

the tranny vent must absolutely have zero back pressure.  the oil seal leak is so common some tranny shops will tell you to run the oil level lower than the fill plug too 

View attachment 91848
Click to expand...
The G50 input shaft has a larger diameter at the seal than the VW style MD4E input shafts. The only reason the that I can think of why Mendeola used 2 seals stacked up was that 2 seals are the same "thickness" as (1) VW seal, so really the outer seal is just a spacer to keep the inner seal from walking towards the engine. 

Reality is there are literally 1000's of 2D's that run just fine without any leaks. But there are a few that are problematic for a variety of reasons. 

 
Sean@Weddle said:
The G50 input shaft has a larger diameter at the seal than the VW style MD4E input shafts. The only reason the that I can think of why Mendeola used 2 seals stacked up was that 2 seals are the same "thickness" as (1) VW seal, so really the outer seal is just a spacer to keep the inner seal from walking towards the engine. 

Reality is there are literally 1000's of 2D's that run just fine without any leaks. But there are a few that are problematic for a variety of reasons. 
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i dont rebuild 2D's but i see input shaft seal leaks more often then you would think

the "variety of reasons" is exactly what he is looking for........

high RPM use

high torque, flexing input shaft

no real estate on the seals required for the G50 input

loose or missing pilot bearing

scared input shaft

plugged (even slightly plugged) vent, or too small of vent that sand plugs the flow of air

I see it so much that i make a point in telling a customer that regardless of who builds the tranny, if the input shaft seal leaks, its not a warrantable item through me as the installer.  I hate to say that but its because its more common then you think.  there are tranny shops that make custom bushings for the input shaft, others say to run the level lower than stock, and so on

SEAN would there be a way to put an oil slinger on the input shaft just inside the bellhousing, helping the splash from the R&P to not hit the back side of the seals?

 
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Sean@Weddle said:
Yes, 1st and 2nd gears are spinning with the engine in neutral when the clutch pedal is up. But this is in a different oil chamber, so the oil doesn't easily migrate along the input shaft, especially in a car where the trans has a slight downward angle, then the oil goes towards the front of the trans and away from the bell housing. 

The G50 input shaft has a larger diameter at the seal than the VW style MD4E input shafts. The only reason the that I can think of why Mendeola used 2 seals stacked up was that 2 seals are the same "thickness" as (1) VW seal, so really the outer seal is just a spacer to keep the inner seal from walking towards the engine. 

Reality is there are literally 1000's of 2D's that run just fine without any leaks. But there are a few that are problematic for a variety of reasons. 
Click to expand...
Yeah, good point. Now I’m gonna stop warming up my chit. Engine bills go to you, right? :biggrin:

 
You guys all rock, this site is unbelievable for information.  Thank you

 
John@Outfront said:
i dont rebuild 2D's but i see input shaft seal leaks more often then you would think

the "variety of reasons" is exactly what he is looking for........

high RPM use

high torque, flexing input shaft

no real estate on the seals required for the G50 input

loose or missing pilot bearing

scared input shaft

plugged (even slightly plugged) vent, or too small of vent that sand plugs the flow of air

I see it so much that i make a point in telling a customer that regardless of who builds the tranny, if the input shaft seal leaks, its not a warrantable item through me as the installer.  I hate to say that but its because its more common then you think.  there are tranny shops that make custom bushings for the input shaft, others say to run the level lower than stock, and so on

SEAN would there be a way to put an oil slinger on the input shaft just inside the bellhousing, helping the splash from the R&P to not hit the back side of the seals?
Click to expand...
We actually want oil to get to the back of the seals, that it what helps keep them lubricated and cool. What we don't want is all of the things you listed above. Hard to fix a lot of those issues. Ideally, we would have needle bearing behind the seals to help support the input shaft, Albins has this, but even those input seals leak after time. 

Rockwood said:
Yeah, good point. Now I’m gonna stop warming up my chit. Engine bills go to you, right? :biggrin:
Click to expand...
I never said you couldn't drive it easily in 1st gear to get the engine and trans up to temp... :classic_cool:

I've seen people fire up the motors, then head back in the trailer for breakfast. Just letting the engine idle for 5-10 minutes. Think about that input shaft spinning inside that seal without any oil splashing to it for that amount time...

 
You will have to be very carful

Dave Chappelle just got in trouble for using the word

Tranny,  

 
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