Author Topic: Needs some advice on an oil leak (Read 8220 times)

Farmer Dan · « **on:** August 29, 2015, 09:54:34 PM »

After an hour on the road when I park my '72 Eldorado it will leave a puddle of 90wt gear lube. When I check the fluid levels the rear drive gears are low and the transmission is over full. The fluid is leaking from the transmission that is now way past being full. Looks to me like the gear lube is following the drive shaft and being syphoned into the trans. I have not been inside that gear box for several years but I don't recall there being any seals to prevent this. How does one cure this problem?

pehayes · « **Reply #1 on:** August 29, 2015, 10:33:00 PM »

Start by joining the LoopFrame message group over on yahoo.com.

How old are your rear shocks and springs? Were you riding two-up? Were you carrying cargo? Are your shocks the stock length dimension?

There is no seal to keep the oil in the rear drive box. The box is supposed to be BELOW the level of the transmission for normal riding. There is a seal at the back of the transmission at the output shaft. But, you'd have to fill the bellows boot before that transmission seal came into effect. If you are migrating oil, the transmission output shaft seal likely has a helical ridge built into the seal lip. Designed to suck oil INTO the transmission and keep it from migrating out.

I wouldn't do anything until I drained both transmission and rear drive and confirmed a refill to the listed capacity level. DO NOT use inspection or level plugs. Install the quantity specified. You can re-use the existing oil. Just drain and measure for a refill.

You might just need new rear shocks and springs. We need to see your answers to the above.

Patrick Hayes
Fremont CA

Farmer Dan · « **Reply #2 on:** August 29, 2015, 11:50:47 PM »

Quote from: pehayes on August 29, 2015, 10:33:00 PM

Start by joining the LoopFrame message group over on yahoo.com.

How old are your rear shocks and springs? Were you riding two-up? Were you carrying cargo? Are your shocks the stock length dimension?

Rear shocks and springs are original with 26,286 miles on them. Riding 2 up. No cargo. Shocks are stock in all ways. I have refilled both with a measuring cup to make sure they had the correct amount and type of oil in them. Same result. Engine oil is good, trans over full, rear drive low.

rodekyll · « **Reply #3 on:** August 30, 2015, 12:53:01 AM »

The reasonable answer has been given -- negative swing arm geometry. Time, miles, and load have worn out the rear shocks. Get some new ones (or maybe HD takeoffs would work for a cheap experiment before buying new).

Perazzimx14 · « **Reply #4 on:** August 30, 2015, 07:30:09 AM »

Quote from: Farmer Dan on August 29, 2015, 09:54:34 PM

After an hour on the road when I park my '72 Eldorado it will leave a puddle of 90wt gear lube. When I check the fluid levels the rear drive gears are low and the transmission is over full. The fluid is leaking from the transmission that is now way past being full. Looks to me like the gear lube is following the drive shaft and being syphoned into the trans. I have not been inside that gear box for several years but I don't recall there being any seals to prevent this. How does one cure this problem?

There is seal on the back of the transmission where the U-joint connects to the output shaft. The rear drive oil would have to get by this seal to overfill the transmission. I would thing its an impossibility. If the seal was leaking that badly I would think the transmission would fill the rear drive not vise versa.

Kiwi_Roy · « **Reply #5 on:** August 30, 2015, 08:01:41 AM »

Check the temperature of the rear drive after a decent run, I found mine was rubbing on the wheel and getting too hot to touch after about 5 miles.
I thought it was the gears at first but the wheel was getting hot as well.
I concluded the pressure was blowing the oil out of the box into the shaft area, running back as it cooled.

My 72 has the fill level hole too low, later models have it higher allowing more oil, also the pinion housing may be the old style without the oil pathways (2 flats)

At a rally I was told by a long time Eldo owner that the rear shocks should be 13 inches eye to eye giving quite a slope to the driveshaft.

Idontwantapickle · « **Reply #6 on:** August 30, 2015, 02:14:32 PM »

Quote from: Perazzimx14 on August 30, 2015, 07:30:09 AM

There is seal on the back of the transmission where the U-joint connects to the output shaft. The rear drive oil would have to get by this seal to overfill the transmission. I would thing its an impossibility. If the seal was leaking that badly I would think the transmission would fill the rear drive not vise versa.

:1:
It could be that oil is leaving the rear drive but it is not going into the transmission. It may be possible that if the pinion assy is oriented incorrectly that oil could gather in the shaft area due to an inability to drain back from the pinion bearings into the case. Had the rear drive apart?
Hunter

pehayes · « **Reply #7 on:** August 30, 2015, 03:21:52 PM »

Quote from: Perazzimx14 on August 30, 2015, 07:30:09 AM

There is seal on the back of the transmission where the U-joint connects to the output shaft. The rear drive oil would have to get by this seal to overfill the transmission. I would thing its an impossibility.

Not only possible, but intended that way. We don't know what seal he has on the back of the transmission. Some seals, especially where the shaft only rotates in one direction, have helical grooves or ridges on the lip engineered to suck oil in one direction only. Any oil that gets near such a seal will quickly move to the other side of the seal. Motorcycles don't drive backwards, so the transmission output shaft would be a logical location for such a one-directional seal design.

Note this cross section which shows angular or helical ridges intended specifically for that oil migration purpose.

Patrick Hayes
Fremont CA

Idontwantapickle · « **Reply #8 on:** August 30, 2015, 06:00:35 PM »

Quote from: pehayes on August 30, 2015, 03:21:52 PM

Not only possible, but intended that way. We don't know what seal he has on the back of the transmission. Some seals, especially where the shaft only rotates in one direction, have helical grooves or ridges on the lip engineered to suck oil in one direction only. Any oil that gets near such a seal will quickly move to the other side of the seal. Motorcycles don't drive backwards, so the transmission output shaft would be a logical location for such a one-directional seal design.

Note this cross section which shows angular or helical ridges intended specifically for that oil migration purpose.

Patrick Hayes
Fremont CA

I see what you are saying Patrick. The thing is the rear drive doesn't have enough oil volume to fill the space required to reach the level of the transmission seal and overcome the seal. The oil would need to fill the tube enough to overcome the joint support bearing and then fill the boot enough to get in the transmission. The rear drive would have locked up by then.
More likely we don't have enough information. It is entirely possible that Dan has added the correct amount of oil to the transmission but when he found a leak and checked it he found it was high because either it was hot or that when the correct amount is in there it's simply above the check hole and he did not know this before.
More info needed.

Hunter

Farmer Dan · « **Reply #9 on:** August 30, 2015, 08:05:02 PM »

Some good advice, thanks guys. I've never noticed any heat from the final drive but I'll check it next time I get to take a ride. Here is a picture taken on 16A in South Dakota. Looks like the back end maybe sitting a little low. I'll give Curtis a call Monday and see what he has in stock for a pair of shocks with a 13" length. Far as I know, nobody has been in side the final drive. My Uncle Jim rebuilt the engine and the dealer rebuilt the tranny both in 1975.

Aaron D. · « **Reply #10 on:** August 30, 2015, 08:12:48 PM »

This is a classic old Guzzi problem. I've seen it on a few old Tontis as well. The shocks are overloaded and either need more preload or stiffer springs, or longer shocks, which would be a problem when the excess load is removed.

Farmer Dan · « **Reply #11 on:** August 30, 2015, 10:04:01 PM »

Quote from: Aaron D. on August 30, 2015, 08:12:48 PM

This is a classic old Guzzi problem. I've seen it on a few old Tontis as well. The shocks are overloaded and either need more preload or stiffer springs, or longer shocks, which would be a problem when the excess load is removed.

I think you know what my next question is going to be. Near as I can tell the original shock should be 12 3/4" an upgrade to a 13" shock was recommended. Riding two up there is 380 pounds on the bike and it was designed to carry 350. So would a 13" shock be good enough? Sorry for all the questions but this is the first time I've ran into a problem with rear shocks.

pehayes · « **Reply #12 on:** August 30, 2015, 10:13:09 PM »

Quote from: Idontwantapickle on August 30, 2015, 06:00:35 PM

I see what you are saying Patrick. The thing is the rear drive doesn't have enough oil volume to fill the space required to reach the level of the transmission seal and overcome the seal. The oil would need to fill the tube enough to overcome the joint support bearing and then fill the boot enough to get in the transmission.

Maybe not. As long as the drive shaft tube leans forward downhill, it should be easy for small amounts of oil to migrate past the bearing/joint interface. Once in the bellows, any amount will get picked up by the joint body and slung and spashed onto the output shaft. Once on the shaft, a helical lip seal will quickly suck it into the transmission. So, a huge puddle isn't required. Just a damp splash that constantly gets pulled away by the seal and replaced by more gradual ooze from the rear. It takes time to happen, but all within feasible parameters.

Patrick Hayes
Fremont CA

Cam3512 · « **Reply #13 on:** August 31, 2015, 05:23:03 AM »

Quote from: pehayes on August 29, 2015, 10:33:00 PM

Start by joining the LoopFrame message group over on yahoo.com.

Have you taken this good advice yet?

https://groups.yahoo.com/neo/groups/Loopframe_Guzzi/info

boatdetective · « **Reply #14 on:** August 31, 2015, 06:26:31 AM »

Where are your riding gloves?!

Aaron D. · « **Reply #15 on:** August 31, 2015, 06:27:43 AM »

The real test is the swingarm angle. More preload if you have it, stiffer springs if you don't, rather than new shocks.

Farmer Dan · « **Reply #16 on:** August 31, 2015, 03:14:14 PM »

Quote from: Cam3512 on August 31, 2015, 05:23:03 AM

Have you taken this good advice yet?

https://groups.yahoo.com/neo/groups/Loopframe_Guzzi/info

I tried, for some unknown reason I can't figure out how to join the group.

Kiwi_Roy · « **Reply #17 on:** August 31, 2015, 03:29:47 PM »

The 13" I was told, is that with or without rider/s ?

Antietam Classic Cycle · « **Reply #18 on:** August 31, 2015, 05:11:04 PM »

Quote from: Farmer Dan on August 31, 2015, 03:14:14 PM

I tried, for some unknown reason I can't figure out how to join the group.

You must have figured it out - I approved you about an hour ago. In any case, it's either click the "+ Join Group" button and tell me why you want to join (this is to weed out spammers) or simply send an email to: loopframe_guzzi-subscribe@yahoogroups.com

Farmer Dan · « **Reply #19 on:** September 01, 2015, 01:04:58 AM »

Quote from: Antietam Classic Cycle on August 31, 2015, 05:11:04 PM

You must have figured it out - I approved you about an hour ago. In any case, it's either click the "+ Join Group" button and tell me why you want to join (this is to weed out spammers) or simply send an email to: loopframe_guzzi-subscribe@yahoogroups.com

Yea I figured it out. Thanks :-)

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Author Topic: Needs some advice on an oil leak (Read 8220 times)