Chasing Transmission Leak; '48 P15

[Sam Buchanan]

My P15 transmission has a large oil leak that has so far remained unresolved....but I'm going to get it this time.   I would appreciate input from those who have been down this path already.

 

Here is a scan from the service manual showing a mod that may be needed on the drive pinion bearing retainer:

 

 

 

And here is my retainer:

 

 

 

 

Am I correct is thinking the lack of a drainage relief at the slinger threads per the manual is preventing oil from being evacuated from the retainer? Should I file/machine a relief as shown in the manual?

 

Also, should the end of the countershaft be sealed to prevent oil migration?

 

 

 

I have some high performance sealer (Flamemaster fuel tank sealant) that I have used many times previously to stop persistent leaks. I'm thinking the end of the shaft needs a sealant "plug" and also a thin coat on both sides of the retainer gasket. Does this sound like a good path to follow?

Edited August 7, 2019 by Sam Buchanan

[soth122003]

Hey Sam,

 

Looking at the book that file cavity is only if the end of the threads are not inline with the slot. As far as leak goes, most of the large leaks are from the main shaft rear bearing oil seal. Mine was leaking like a sieve when I first got mine and it seams like the leak is more forward on the tranny due to the oil running down the bottom of the case to the lowest point especially after the oil is warmed up after driving. The seal change is a breeze after getting the tranny out and the hardest part is putting the tranny back in. Any other oil leaks are usually small and due to a bad gasket or seal, When I had mine out I changed the tranny to clutch mount gasket and the rear seal and no more leaks.

 

Joe Lee

Edited August 7, 2019 by soth122003

[Sam Buchanan]

Joe, the rear 2/3 of my transmission is dry, oil is definitely running down the front end of the tranny and dripping off the protrusion on the bottom. The "end of the threads not in line with the slot" is what I'm failing to understand. I don't see where the threads end and don't see a path for oil to drain out of the threads.

 

Guess I might as well take care of the rear mounts while I'm in here.....think these have timed out? 

 

Edited August 7, 2019 by Sam Buchanan

[soth122003]

Sam.

 

I thought mine were bad. Yours are UGLY. The only other thing I can think of is on the front of the tranny where it mounts to the bell housing is a port. I think it is on the left side of the face about 2/3 from the bottom. When you put the gasket on this hole is covered by the gasket, unlees you have an over drive on your model. If the gasket is torn or broken there, oil will splash through and leak into the bell housing, but that is sometimes accompanied by a slipping clutch. Just looked at my Motors Manual. On the left side of the face connecting to the bell housing, there is a mount hole at the top, a port below it and then another mount hole?, then another port then the bottom mount hole. When you put the gasket on both ports are covered unless you have an overdrive unit installed then there is a different gasket for that unit. I am not 100 percent sure on this so hopefully someone else will chime in on it, since I don't have an overdrive on mine.

 

Joe Lee

[Frank Elder]

It would be criminal not to change that clutch release fork seal while you are at it......

[Sam Buchanan]

Criminal, eh? It's not torn...just a little dirty.......the oil keeps it soft and pliable.....  

Edited August 9, 2019 by Sam Buchanan

[Sam Buchanan]

Decided to modify the bearing retainer per the service manual:

 

 

The threads ended at about 8 o'clock instead of in line with the drainage slot. I applied sealant to all surfaces including the bolt grommets, basically bonding the retainer to the transmission. Hope this stops the leak. The end of the countershaft also received a coat of sealant.

 

FYI, the sealant is a fantastic product, also is a great non-hardening adhesive. It was developed as a fuel tank sealant for the B1 bomber and has sealed over 20,000 RV aircraft tanks. My 20-year-old tanks are still fuel-tight. If anyone is interested in having this in their shop here is a source:

 

https://shop.vansaircraft.com/cgi-bin/shop.cgi?ident=1565367378-16-348&browse=misc&product=proseal

 

If stored in a refrig it will keep for years.

Edited August 9, 2019 by Sam Buchanan

[9 foot box]

   My books say you need a gasket. Transmission to Clutch Housing, Group 21-3-4, part 852 623. The whole transmission rebuild kit is Group 21-3-1, part 1064 745. You could probably make a bit thicker gasket, than the set supplies. It seals the counter shaft and shift rails from leaking out, from a metal to metal surface. I'm guessing the gasket was eliminated when they removed and applied an RTV sealant. The input shaft bearing retainer, should be shimmed, for proper gasket thickness, page 211. The complete kit came with various thickness retainer gaskets. Or make your own, to the .005" crush. 

[Sam Buchanan]

34 minutes ago, 9 foot box said:

   My books say you need a gasket. Transmission to Clutch Housing, Group 21-3-4, part 852 623. The whole transmission rebuild kit is Group 21-3-1, part 1064 745. You could probably make a bit thicker gasket, than the set supplies. It seals the counter shaft and shift rails from leaking out, from a metal to metal surface. I'm guessing the gasket was eliminated when they removed and applied an RTV sealant. The input shaft bearing retainer, should be shimmed, for proper gasket thickness, page 211. The complete kit came with various thickness retainer gaskets. Or make your own, to the .005" crush. 

 

I'm using all the gaskets per the service manual. The bearing retainer was also checked for proper end play per the manual. The countershaft doesn't have a metal to metal contact. You can see the faint coloration in the photo where it resides just below the junction of transmission to bellhousing. 

Edited August 10, 2019 by Sam Buchanan

[Cold Blue]

Sam - I have the same leak that you described on my 48 P15 tranny. It's not too bad, but enough to leave a small puddle on the garage floor. I am going to tackle it this fall when the weather cools a bit. I think my tranny is missing the bell housing to tranny gasket, as I can see RTV at that junction. Or maybe it has a gasket plus RTV? We will see. Thanks for the tip on modifying the bearing retainer. I will look at the slinger threads when I have the tranny out to see where they end, and if the slot is necessary. May do the slot anyhow just for insurance. When you get her back together would you let us know if the leak has been cured? 

[Sam Buchanan]

Will definitely post an update, hope it is a good one. ?

 

This is my second go at fixing the leak. First time the bellhousing and retainer gaskets were replaced but the leak was as bad as before. Upon teardown this time it was obvious the oil was coming through the retainer gasket and possibly out the forward end of the retainer. This car has had a significant leak for a long time based on the buildup of crud in the area.

 

This time I'm added the sealant to the repair, really don't see how oil can escape this time. Both sides of the retainer gasket got a thin coat of sealant and there was squeeze out all the way around the retainer. The only other place I see where oil could leak is at the upper shift rail and the big gasket will get some sealant in that area when the tranny is reinstalled. The lower shift rail already had a plug and it and the countershaft got a dose of sealant.

 

New motor mounts arrived today then we'll find out if the repair worked.

Edited August 10, 2019 by Sam Buchanan

[P15-D24]

Is the welch plug on the gearshift rail in place and not leaking?

[Sam Buchanan]

41 minutes ago, P15-D24 said:

Is the welch plug on the gearshift rail in place and not leaking?

 

The lower rail has a plug and it appears to be dry, I had applied sealant to it the first time. The upper rail does not have a plug and one isn't shown in the manual.

 

 

 

 

The sealant is non-hardening and can easily removed if needed, but I'm hoping I never see this scene again! 

 

 

Oddly the gasket has a hole where the upper rail is located. Guess this is a universal gasket that is also used for other applications? The gasket will get trimmed this time to remove the unneeded portion on the bottom.

 

Edited August 10, 2019 by Sam Buchanan

[P15-D24]

Was the plug set, ie flattened slightly in the center or just stuck in?

[Sam Buchanan]

28 minutes ago, P15-D24 said:

Was the plug set, ie flattened slightly in the center or just stuck in?

 

Don't recall but I didn't see any evidence of it leaking. There was a lot of oil getting past the retainer gasket, I suspect it may have been too thin to seal adequately considering the end play specs for the bearing. The large gasket in the photo is the one that was in place and it is dry around the plugged shift rail.

Edited August 10, 2019 by Sam Buchanan

[Cold Blue]

Sam - what is that vertical slot for at the bottom of the gasket (the part you are going to trim off..) I see that you have applied sealant to close the top part of the vertical slot. The gasket set I have has that same vertical slot at it's bottom. If the top of the slot was not sealed it is going to leak, right? I really don't like that. Do we have the right gasket set??? Why would the gasket manufacturer make a gasket that wasn't continuous?? Got any ideas? The only thing I can think of is that is indeed a universal gasket and some other model of tranny has a fin or something where that slot is....

[Sam Buchanan]

27 minutes ago, Cold Blue said:

Sam - what is that vertical slot for at the bottom of the gasket (the part you are going to trim off..) I see that you have applied sealant to close the top part of the vertical slot. The gasket set I have has that same vertical slot at it's bottom. If the top of the slot was not sealed it is going to leak, right? I really don't like that. Do we have the right gasket set??? Why would the gasket manufacturer make a gasket that wasn't continuous?? Got any ideas? The only thing I can think of is that is indeed a universal gasket and some other model of tranny has a fin or something where that slot is....

 

No sealant was applied to the gasket, you are seeing the bellhousing through the slot in the gasket (well, maybe there is some Permatex on the bellhousing). I don't know the purpose of the slot, but I suspect it is there so you could install a new gasket without pulling the pinion shaft all the way out of the bellhousing. The gasket won't leak at the slot if the bearing retainer is sealed properly, the tranny will be oil-tight.

Edited August 11, 2019 by Sam Buchanan

[Cold Blue]

Sam - one last question and I'll go away. You say "if the bearing retainer is sealed properly, the tranny will be oil tight". So the gasket between the bell housing and the tranny is really just a spacer? And I right? Thanks Sam.

[Sam Buchanan]

2 hours ago, Cold Blue said:

Sam - one last question and I'll go away. You say "if the bearing retainer is sealed properly, the tranny will be oil tight". So the gasket between the bell housing and the tranny is really just a spacer? And I right? Thanks Sam.

 

No need to go away, we're plowing good ground and maybe our shop floors will be cleaner because of our efforts.  

 

As it appears to me, the big gasket is for sealing the shift rails. The lower rail has a plug but the upper is open. The gasket within the retainer is responsible for keeping oil in the retainer. If oil gets out of the retainer, the big gasket won't prevent it from running down into the the slot in the gasket, also into the clutch housing, then onto the shop floor. This is what was happening with my car.

 

I wonder if the upper rail isn't plugged because it resides above the oil level in the trans housing. But I'm not taking chances and will add a thin coat of sealant under and on the big gasket in the area of the upper shift rail to hopefully prevent oil from getting out of the rail bore. The slotted end of the gearshift fork guide rail will also get a dab of sealant. (see manual scan and the small slotted rod in my photo)

 

If the rail bores are sealed by the plug and big gasket, the countershaft bore is sealed and the retainer is sealed, and the retainer is draining oil back into the trans housing as it should I can't see any other place for oil to escape the forward end of the transmission. There can be leakage at the shift housing and tailshaft, but those areas can be addressed with the transmission in the car.

Edited August 11, 2019 by Sam Buchanan

[Cold Blue]

Thanks Sam for the info. I think you are right about the gasket. I will be tackling the oil leak in my tranny soon, and the info you have provided will be valuable! Especially the pics and your really good way of explaining things. I don't have any tranny leaks except for the forward end of the tranny. I like the guide bolts you have to align the tranny when it is reinstalled. Seems like these tranny's can be a PIA to install if you don't have those guide bolts.

[Sam Buchanan]

These motor mounts should have a few more years in them.....but I decided to replace them anyway......pretty bad when you have to replace stuff every 72 years..... 

 

 

The reason there is no photo of the lower mounts is because they were.......GONE!  As in "they done left the building....gone".

 

I was dreading getting enough clearance to swap out the the mounts but there was more than enough to pull the old and insert the new. PlymouthyAdams, think this might help my clutch chatter? 

[Cold Blue]

Sam - glad to hear there is enough clearance to install the back motor mounts. I have read some posts that say the lower left (driver's side) mount suffered from not enough space between the motor and the tranny tunnel to remove the motor mount bolt. I plan on just jacking the motor up just enough to remove the old biscuits, then slide the new ones in. I have replaced the front rectangular shaped motor mount; it was a piece of cake. (The mount that was there was a flattened piece of radiator hose, thru bolted; yikes!) Amazing what you find that has been done by previous owners!

 

I have some clutch chatter too, when pulling out. I am hoping that bad motor mounts are the problem. My mounts do not look as deteriorated as yours, but they probably need replacement. A previous post also mentioned that bad shackle bushings may also cause clutch chatter. I am going to check those too.

[Sam Buchanan]

Engine mount travails are being discussed in this thread:

 

http://p15-d24.com/topic/47787-48-plymouth-reverse/?tab=comments#comment-539428

 

New mounts have been installed but it seems likely they are made of rubber that is too hard and causing vibration problems.

Edited August 14, 2019 by Sam Buchanan

[Sam Buchanan]

After a few short test trips around town it appears the transmission leak is fixed. I think the key was getting the bearing retainer sealed so it will drain oil back into the transmission instead of on the shop floor.

Edited August 14, 2019 by Sam Buchanan

[Cold Blue]

Congratulations Sam! It is always rewarding to get something repaired correctly. Now I hope that the new biscuits are not too hard and your vibration problem goes away...