Another leaking final drive - advice gratefully accepted

[Guest]

Hi everyone
Had my 1984 GS1100GK (with side car) for about 7 months and found your site an absolute boon. I have fixed the stator/rectifier wiring as per the technical papers and it works a treat.


The problems started after driving down the highway for about an hour and when I stopped, there was oil all over the rear wheel. Checked the final drive oil level and it was not dangerously low so I went home again. When I got home, I pulled the rear end apart and found one of the bolts holding the "Driven Joint Assembly" onto the wheel had undone and rattled around inside the hub. The seal was dented and it was leaking. When I removed the "Driven Joint Assembly" from the wheel, I found that the splines were almost non-existent.


Purchased a new "Driven Joint Assembly", 8 new longer thread high tensile allen socket bolts and the $70 final drive seal and proceeded to re-assemble the lot. The locking tabs were all damaged so I went for medium strength lock tight and fixed the new "Driven Joint Assembly" to the rear wheel and then carefully tapped the seal into the final drive after making sure the shaft and seal recess were undamaged and free from nicks or wear ridges. After lubricating the splines as recommended, the wheel went back and the bike back together. Topped the oil level to just on the bottom of the threads and went for a ride.


Oil leak still there. Sprays over the tyre when travelling and then dips out of the hub leaving a CD sized oil patch on the driveway. Went for several rides and the result was the same. Oil level gradually dropped but could still be seen about 5mm below the threaded section of the oil filler hole.


Pulled it all apart again and noticed that the oil looked like it was only on the inside hub of the wheel and had not touched the newly clean "Driven Joint Assembly". Took the oil filler plug out and pressurised the final drive with the compressed air and found the small oil breather hole. Tried again with the hole blocked by my now oily finger and the whole assembly held pressure for a good 2 minutes with no evidence of any oil leaks. There was no washing of the grease that had transferred to the seal lip so I thought it must have been over filled by yours truly, so I put it back together again and ran it on a stand for 10 minutes in top gear at cruising revs with no leak. So I went for another ride and after 20 minutes in city traffic not getting over 70 km/hr, the leak was still there, same as before, which I suppose is not surprising as I had done nothing except lower the oil level a bit.


Came home and pulled it apart again. Still noted that the"Driven Joint Assembly" was not covered in oil, just inside the hub. Could see nothing else so I assumed that I had damaged the first seal, so I bought another $70 seal and replaced it again being EXTREMELY careful and using a PVC pipe fitting to gently drive the seal home, as per site recommendations, after checking that the seal came with seal lip lubrication to prevent seal burn (pretty sure I did NOT do this the first time). Cleaned it all up and put it back together then left it for a couple of days.


Just built up the courage today to drive it to work and surprise surprise, the leak is still there, just the same as before. So I thought that the oil may have been to "thin" and as a result was squirting out the breather hole. So I went to Suzuki and bought some more 80W90 Gear oil (Motul GearBox SAE 80W90 Mineral with MoS2), drained the unit and refilled with new oil to just below the threaded section of the filler hole and went for another ride. The dark grey oil is easier to spot now and the leak is still the same!


My guess is that for some reason, the oil is squirting out of the breather hole into the wheels hub. Some of the oil sprays onto the wheel/tyre when travelling but it still pools in the hub and when you stop, 30 seconds later, oil starts to drip steadily from the hub. I am thinking of making a temporary filler plug with a hose attached so that I can remove the possibility of case pressurisation but apart from that, I'm stumped. I have NOT changed the input seal or the large O ring under the final drive internal cover plate but I could see no evidence of oil from these locations.


I really enjoy the bike and I look forward to your advice so I can take it for a really LONG ride.


Cheers

PS. I'm no novice when it comes to motor bikes/cars and have been working on/rebuilding/reconditioning both for over 35 years but being human, can still make mistakes.

[rustybronco]

It would be highly unlikely that the oil would be coming out from the breather hole.

Have you given thought about separating the two halves of the final drive to inspect the case o-ring and sealing surface of the ring gear? The only things I can see different between running the bike on a stand and out on the roadway, is the orientation of the pinion angle and the ring gear running unloaded.

[oracwa]

And now to the next installment.

I ordered a replacement final drive from the US and had to wait for a couple of months for delivery ($13 purchase and $75 delivery). Then I dissembled the bike again and then disassembled the final drive. There were no signs of oil leaking from the seal as the coating of grease on the splines and the outer seal face were still intact and no washing was apparent. I also inspected the O ring for damage or signs of leakage but could find none. Rightly or wrongly, I carefully removed the shaft seal (used only for 20 mins from new) and inspected it. It displayed no signs of damage or wear and it also had good tension against the shaft. So I removed the seal from the newly delivered unit and re-fitted the seal removed from the old unit. I did take pains to ensure that the seal lips were running on the smooth shaft surface and all appeared to be well seated.

After re-installing the drive/wheel/etc I took it for a ride at 100 km/hr for 5 minutes only to be greeted with that unmistakable aroma at the next stop sign. Exactly the same result with the replacement drive. The only grey area I can think of is that I did fill the drive about 4 threads past the bottom of the filler hole and my question is, how critical is the amount of oil in the final drive? I have been looking around the site and it seems that leaking final drives are a common occurrence and I would be good to find a common cause.

Thanks again for your help.

[Grimly]

Leaky final drives aren't all that common. For me, mine are always filled to just at the bottom thread of the filler hole and the only one I've had leak was a quite distinct seal failure at 100K on the 79 bike. Replaced that, and neither bike has given any other FD trouble. I can understand why you wanted to save that very expensive seal, but I'd have simply fitted the used part complete with its own seal, as the chances are it would be fine for decades yet.

[Grimly]

Damned forum software won't allow me to add an edit today. If you closely inspect the new-ish seal and see if it's still got a knife-edge to the lip(s) (I don't recall if it's a single or twin-lipped seal), and if it's not tight enough on the shaft/sealing shoulder, you can tighten the spring just a touch. This is not a bodge, it's a technique. You take out the tension spring, cut it, and overlap it by a few mm so it completes the circle again. There's a knack to doing this, so don't over-do it.

[oracwa]

Thanks Dave

It is a twin lipped seal and I will compare the old seals spring with the new one. It would explain the issue if both seals came from the stock and there was a "manufacturing fault". I now have the weekend's work set out. I will keep you posted on the result.

Cheers
Scott

[oracwa]

Checked the seal springs of the past two seals and they were as near as I could measure, the same. Even swapped the springs between the seals and tried both on the old final drive shaft and they were tight. Wracked my brain and thought that the seal that I installed in the new drive was the same so... I removed the oil filler plug and screwed in a rubber hose about 2 foot long and cable tied it to the carrier. Went for a ride and ... no leak. I then went for a longer high speed drive and ... still no leak. I then had a terrible thought that the oil may have gone completely so I unscrewed the hose and checked the oil level ... still the same, at the bottom of the threads. I have since ridden about 300km at varying speed with no sign of a leak. Now all I need to do is have the courage to re-fit the filler plug!

Do you think that it was possible that I had overfilled the drive and it was always squirting out of the overflow into the wheel hub?

[Grimly]

That is very possible - some units are fussy about the level. You wouldn't think so, as initially it seems there's really not that much in them to affect things, but it's a lively internal invironment with a lot of oil being thrashed around.
I've always just levelled off at the bottom of the threads, so the overfill problem hasn't reared its head.