Leaking transmission output shaft seal - how do I change it?

[Simon_London]

I have traced a gearbox leak to the transmission output shaft seal - oil coming out of the boot.

Any tips on how to change this with engine / gearbox in the frame?

It occurs to me I will have to stop the shaft rotating whilst undoing the hex output nut. How do I do this with the engine / gearbox in the frame and swinging arm removed?

I don't have air tools / impact tools.

Will the seal be difficult to remove and replace?

And I believe care will be needed with the speedo drive / ballbearing thingy...........

Any help appreciated.

Simon

[Wayne Orwig]

What model bike is this?

Likely, you can pull the swingarm, and CAREFULLY pry out and press in a new seal. Without taking the nut off of the layshaft. If you damage the surface of the inner piece by the nut, you will have messed up big.

BUT:

1: It may be leaking past the o-ring that seals the around the inside shaft. If that is leaking you will need to take off the nut.
2: If a bearing is failing, that may look like a simple seal leak.
3: Most big blocks let fluid from the rear drive migrate all the way to the transmission. If the rear drive is over filled, the shocks are shortened, or the bike overloaded, you may just be seeing fluid from back there.

[Simon_London]

Thanks OMG !

Bike's a G5.

It's got 1/2" longer shocks - I know this may stress the UJ but others seem to get away with it.

I'll check the level on the bevel box. I haven't touched it for thousands of miles, so I doubt that this is the source, although I suspect there may be extra gearbox oil that has got in there.

How will I know if the bearing is failing and how do I get that nut off if I need to? Any way of know if the O-ring is leaking?

I thought I'd change the output shaft seal and see if that sorts out the problem. Will a small screw driver under the inside lip be suitable?

Simon

[Wayne Orwig]

Bike's a G5.
It's got 1/2" longer shocks - I know this may stress the UJ but others seem to get away with it.
I'll check the level on the bevel box. I haven't touched it for thousands of miles, so I doubt that this is the source, although I suspect there may be extra gearbox oil that has got in there.
How will I know if the bearing is failing and how do I get that nut off if I need to? Any way of know if the O-ring is leaking?
I thought I'd change the output shaft seal and see if that sorts out the problem. Will a small screw driver under the inside lip be suitable?

Larger shocks means it should not be rear drive lube.

Getting the seal out, in place, means being VERY careful not to touch that inner surface. I have done it a couple of times. I thin I drilled small holes in the seal and ran screws sheet metal screws in. Plus prying and such.

You should be able to check for too much free play in the bearing by hand easy enough. If the oring is leaking, you will likely see a lot of lube around the nut that won't be there if it is the seal. The speedometer drive sort of 'shields' the nut, so you should able to tell. I don't think it is practical to change the oring with the transmission in place. Maybe it is, but there are a lot of things to work out.

[Simon_London]

Really appreciate your advice - I'll let you know how I get on.

[Simon_London]

OMG. I am going to use the drill / self tapping screw method to extract the seal.

If I understand correctly, the seal is not seated against any alloy gearbox casing directly behind it.

Am I right in thinking there is a space behind the seal and beyond that by ?5-10 ml or so, the bearing?

Therefore when I put the new seal in I should make sure it goes in the same depth as the original as there is nothing to stop it going back too far?

Simon

[pete roper]

It may not be the seal. Nine times out of ten it's the O-ring. Replacing the seal won't fix it. The machine is now nearly forty years old. Isn't it worth taking the box out and doing the job properly?

Pete

[ed.bremner]

Hi All,

Really glad you asked the question Simon_London as I have exactly the same job to do shortly on 77 T3 Cali

I have so much oil now leaking from gearbox, that I found it had migrated the whole way up to the bevel box and way overfilled that.

I have been really struggling to see how best to replace this oilseal...and then you posted.  I admit I had not realised there was also an o-ring there.  I was also hoping to change the seal with the gearbox in place, but if there is another o-ring, then guess it is worth getting the box off and doing the job properly, with all seals, back and front.   Mmmmm, maybe trying to sort out the gear-change 'brick-in-bucket' syndrome at same time.

So....can I add my plea to that of Simon.  Does anyone know where the best 'how-to' for undertaking the replacement of this both seals and the o-ring are.  The Haynes seems a bit thin on the subject.  Or has it been covered on this esteemed forum in the past, or could anyone give a few words of advice.  It looks like both Simon and I would appreciate it.  <edit> Just found Pete's very explicit gearbox-rebuild notes on 'This Old Tractor' - BRILLIANT!  </edit>

I was trying to keep the Cali-Rossi going till the end of summer before doing this work, but now leak is so bad, I don't think I can really put it off.  My brother has suggested I might be able to borrow something to tide me over for rest of Summer.  Looking at possibly a Benelli 654 or a Cagiva Elefant....Any thoughts?

Thanks again Simon and all

eib

[Simon_London]

My feeling is that the O ring replacement will need removal of the gearbox.

The seal round the speedo worm drive looks very doable in the frame. I'll whip the swinging arm off next weekend. If that doesn't fix it, off to Guzzi hospital...

[pehayes]

Therefore when I put the new seal in I should make sure it goes in the same depth as the original as there is nothing to stop it going back too far?

I used a PVC pipe fitting to make a simple driver to install the seal square and to proper depth.  I need to run out on family business today.  I'll post a pic and the dimensions later.  I made a duplicate for Charlie Mullendore.  Perhaps he will see this and post if he has time.

When you install the seal, you need to be careful that the 'lip' does not catch and fold over.  You'll dislodge the seal's tensioning spring if that happens.  Install it just very slightly and then inspect.  If you see any part of the lip catching then use a toothpick to seat it properly on the sealing surface.  Go at it in several very small steps.  Once the lip is fully in contact with the sealing surface, then you can drive it home fully.

Driver specs later.

Patrick Hayes
Fremont CA

[Stevex]

I had to remove the gearbox again after a full bike rebuild when I noticed a leak from the same area.
To remove the nut (and replace) requires an air tool. I took it to a local garage to loosen off the nut and tighten it up again, as I don't have air tools either.
Make sure the new seal you fit is Viton, brown in colour.



You'll see the seal I fitted is a (Viton) dual lip, so the upper lip doesn't quite mate, but it's only a dust seal. It's the lower oil seal that matters. The old blue seals were / are single lip.

[rodekyll]

All I have is a tip for the seal removal -- nothing about the discussion of if it needs it:

If you don't have the proper seal puller tool, drilling three equidistant holes and then using standard machine screws (like #6's -- depends on what size hole you drilled) is as good and safer than self-tappers.  Self-tappers are wedge shaped and wedge into the seal, spreading it.  They also have a sharp tip looking for something to gore, which will be whatever is directly in its path. This makes it harder to pull the seal and can damage stuff.  Machine screws will grab the sides of the hole without spreading it and then push flat tips against whatever they bottom out on, so you can use the three screws as the actual puller -- just keep screwing them in even, small increments until the seal comes out far enough to grab.

 . . . now about that long shock -- it's giving a positive angle to the swing arm which puts the rear drive below the transmission.  That should hinder grease migrating up the tube and shouldn't be an issue FOR THIS PROBLEM.  What matters with the overall shock length is what angle the swing arm has when the bike is loaded.  If the weight and all of the bike gives you a fairly neutral swing arm angle, stress on the u-joint should be no more than standard.  If you're always at a positive angle then the u-joint gets stressed and the rear suspension has more of a tendency to "jack" up and down. 

I run long shocks on my SWB Tonti because of the additional preloading.  I run it very heavy and standard length shocks don't give me a neutral swing arm angle with the spring rate I want.  WIth standard length shocks the swing arm was always in a negative angle (loaded) and I had a grease migration problem.

Hope this helps.

[v7john]

I made these tools to get the nut off the output shaft when I had to go in there years ago (to fix a broken return spring, I think).

The top one is a spanner with the ring ground down so it will fit in the output tunnel of the gearbox and reach the nut. It's cut so I can get a length of pipe over it or wack it with a hammer.
The second is a piece of a drive shaft connecting sleeve welded to another spanner.
The cut socket at the bottom is not for this job but to get the clutch hub off the other end of the gearbox.

I remember the splined tool was held in the vice and the other one turned with a length of gas pipe.

[pehayes]

Sorry to be late in replying.  I got hung up with a local tragedy.
This is the driver I made for installing the output shaft seal into the 5-speed, big block transmission.  I just glued some PVC fittings together and put them in my lathe to cut the dimensions.  I had a transmission at hand at the time so I could fit and test.  The critical internal dimensions clear the splined shaft and the securing nut.  The outside dimensions slide into the cast housing.  The depth of the contact 'lip' is critical for positioning the seal onto the rotating seal surface of the output shaft.

When I installed a seal with transmission in place on a bike, I went very slowly and carefully.  I just set the seal into grip position with a tiny rap.  I then inspected and could see that the lip was likely going to bind on the surface and fold outward.  I used a wooden toothpick to probe around the lip and get it all seated properly.  Then another rap and another inspection.  One confident that the lip was properly on the sealing surface I could easily drive the seal to home position.













Helps to have  lathe!

Patrick Hayes
Fremont CA

[Simon_London]

Wow. Nifty!

[Simon_London]

Did the output seal yesterday.

As far as I can tell the leak has stopped, but a few more miles needed to be sure. The old seal looked distorted (?by heat)

Pretty straightforward.

I would advise using a machine screw near the edge of the seal, through the rubber not the metal. As you wind in the screw it pushes the seal out.

You will need some plastic tubing or deep socket to push in the new seal and clear the nut in the middle.

There is a lip on the transmission case casting casting - just push it in till it stops.

Loads of moly grease all over the UJ and drive shaft splines and good to go.