73 eldo, rear bevel box leak

[bigbikerrick]

Hello folks, my eldo has the bevel drive with the finned sump cover on the bottom. I have replaced the cover gasket twice, and still have a weep from the area. I also smoothed out the mating surface of the cover with some sandpaper on a flat surface to make sure it isnt warped.  I still get some oil weeping from the area, that gets on the tire sidewall. Its not a big leak, but builds up when parked, and after a few days there is a half dollar sized puddle on the floor , under the tire.  I have previously replaced the big seal, the paper gasket, and even the small inner seal, so I am pretty sure its not from those areas . I am running out of ideas, and dont really want to use any sealant such as hondabond on it, since the cover has to be removed to change the lube.  I have seen where someone had part of the fins machined down to a flat surface, and installed a drain plug. to drain the fluid. in that case, I guess some sealant can be applied to the gasket, but I dont really want to do that if there is any other alternative, such as a thicker gasket, etc
Do you guys have any other ideas/suggestions that may help?
thanks alot
Rick..

[73 sport]

   Permatex form-a-gasket #2, non hardening, allowing item to be removed.

[73 sport]

   PS Use with gasket and coat both sides.

[guzzisteve]

Also called Professional Black.

[pehayes]

Start by cleaning fastidiously and then spraying the gasket seam area with the cheapest spray foot powder you can find.  Oil weepage will show up in the otherwise pure white background.

When the rear drive is at rest, the "high tide" level should be below the lips of any of the seals.  You could remove the seals and it wouldn't leak.
Is it possible you are overfilling the rear drive volume?
Here's a rare one.  Is it possible that your transmission output seal is the culprit?  Oil would leak out of the transmission and down along the drive shaft gradually over-filling the rear drive.  Usually shows up as some leakage around the u-joint boot but maybe not.

Patrick Hayes
Fremont CA

[Vagrant]

I bet the casting has a porosity area or crack.Maybe fill with kerosene after spray on powder. It should leak quickly.

[Antietam Classic Cycle]

If you'd like to pressure test it, I can lend you the fixture that Patrick made for me years ago.

[TOMB]

Don't forget the small seal inside the housing.

You can't see it unless you disassemble the diff.

The seal is installed backwards that is the spring side faces the inside of the diff.

The parts diagram show it and is on the axle nut side(right side) as  assembled

TOMB

[Antietam Classic Cycle]

Don't forget the small seal inside the housing.

You can't see it unless you disassemble the diff.

The seal is installed backwards that is the spring side faces the inside of the diff.

The parts diagram show it and is on the axle nut side(right side) as  assembled

TOMB

I have previously replaced the big seal, the paper gasket, and even the small inner seal, so I am pretty sure its not from those areas .

[bigbikerrick]

Thanks guys for all the suggestions. I am going to drain the housing and measure the amount of oil that comes out, to rule out the transmission output seal. Thank you Charliefor the generous offer to lend me the pressure tester. I will let you guys know what I find, and check all the things mentioned. I have found porosity in other Guzzi castings.I will have to rule that out. I will get back to you guys with what I find
Thanks again,
Rick

[Moparnut72]

Here's a rare one.  Is it possible that your transmission output seal is the culprit?  Oil would leak out of the transmission and down along the drive shaft gradually over-filling the rear drive.  Usually shows up as some leakage around the u-joint boot but maybe not.

I had something similar happen to my R75/5. The seal on the input shaft of the gear case failed. The swing arm side with the driveshaft was a separate oil reservoir. Oil from this leaked into the rear drive causing it to leak from the breather. At least this is how I remember it, it was a long time ago.
kk

[bigbikerrick]

Today, I removed the cover, catching all the oil in an aluminum foil baking pan I stole from my wife. The quantity was correct. I plan to fill the housing with kerosene, actually stoddard solvent that I have on hand, and then use the foot powder spray to look for signs of seepage.  I  will report back.

Would it be helpful to remove the final drive, and check the mating surface with a straight edge, or use sandpaper on a flat surface to check for any  warpage ?   I did this to the sump cover, already previously.
thank you
Rick.







 

[Antietam Classic Cycle]

Would it be helpful to remove the final drive, and check the mating surface with a straight edge, or use sandpaper on a flat surface to check for any  warpage ?   I did this to the sump cover, already previously.

Yes.

[guzziart]

My $0.02.....After replacing all the seals & paper gaskets on my '87 Lemans back in 2011, it still leaked.  Shortly thereafter I went back in there and realized my problem was the shim plate.  Over the years, a corrosion path had developed on each side allowing oil to leak between it and the paper gaskets.  I didn't think the amount of corrosion or eroded material would be a problem since the shim cleaned up well but I was wrong, the paper gaskets would not compensate for the slight erosion of material that had taken place.  A new shim plate & paper gaskets are still doing their job 15 years later...no leaks!  So, for anyone else having rear drive leaks, you may want to make sure your bevel gear shim looks like its in good condition...not corroded while you're in there.  Rick...Good luck!

[bigbikerrick]

Thanks Guzziart and Charie for the suggestions. yesterday I removed the rear drive from the bike and checked the mating surface of the drive housing using some 400 grit sandpaper on a glass plate, and it did show some areas where the paper didnt touch. It took me a while, but I did get an even surface  eventually.
I plan to put it all back together with a smear of non hardening permatex on both sides of the gasket. I am hopeful that this does the trick.
Rick.

[BMCMOTO]

Sometimes it helps to put a mild bevel on the threaded holes in the housing. Overtightening frequently causes these holes to pull a bit, glassing the surface also helps. When working at GT Motors I found the same issue with the valve cover bolts in the head. I think people frequently use way too much torque on small bolts, I know I'm guilty some times for sure. I have started using a torque wrench more frequently on small stuff just to be sure, I'm always surprised how little it takes. I have started using 1/4 drive ratchets with 3 inch handles for small bolts, still find I over torque them sometimes.

Brian

[bigbikerrick]

Sometimes it helps to put a mild bevel on the threaded holes in the housing. Overtightening frequently causes these holes to pull a bit, glassing the surface also helps. When working at GT Motors I found the same issue with the valve cover bolts in the head. I think people frequently use way too much torque on small bolts, I know I'm guilty some times for sure. I have started using a torque wrench more frequently on small stuff just to be sure, I'm always surprised how little it takes. I have started using 1/4 drive ratchets with 3 inch handles for small bolts, still find I over torque them sometimes.

Brian

Thats good advice Brian. do you just use a hand drill with a larger sized bit  to carefully bevel the holes slightly? I "glassed" the surface of the threaded portion of the bevel drive housing, and re assembled it with a smear of non hardening permatex on both sides of the gasket, and so far no leak. the mating surfaces are pretty narrow, so I can see where a slight imperfection could be a leak pathway.
Thanks, Rick

[John A]

A couple things I do is use a rethreading die on the holes instead of a tap because it won’t remove material, especially important on aluminum, then a larger drill bit by hand to chamfer the holes. I use a drain plug that is not the short variety. After , when I put the level plugs in , I screw them in a little then l rinse the oil off the sealing area with mineral spirits so it doesn’t leave a small oil stain around the plug.

[BMCMOTO]

I have a couple of small 45 degree cutters that I either spin with my fingers or a tap wrench, gently, gently. I do occasionally spin the larger one with a drill motor depending on material, steel vs aluminum etc. I would mention where I got them if I knew, I've had the for over fifty years and memory fades. I have used a drill bit in a pinch. I would do this relief after ensuring a flat surface.

Brian