calling all loop gurus - transmission oil in U-J boot - UPDATE

[lazlokovacs]

ok, the super loop made a strange noise once so I happily ignored it.

3 times later I had to take action.

Kind of sounds nasty, like its coming from the gearbox/ rear drive-ish, sort of sounds like the centre stand hitting the ground momentarily. It happens once then goes away. Last 2 times it did it I had just started off.

Hmmm

Pulled back the boot to check the U-J and there was a LOT of transmission oil in there.

U-J is fine.

Drained the transmission and measured. Only 500ml in there.

Tranny and rear drive oils were changed 4000miles ago along with my new clutch

Engine oil more recently

Has been basically many many miles of highway since then

any thoughts??

cheers

[pehayes]

U-J is fine.

Explain what you mean by u-joint is fine.  How did you analyze it?
Use a mechanics stethoscope and probe various locations.  Might be the carrier bearing for the u-joint.  Might be inside the rear drive.  Might be in the transmission.  See if you can isolate it.  Turn the rear wheel by hand.  DO NOT run the bike in gear up on the centerstand.

There should not be appreciable oil in the bellows boot.  Were you heavily loaded with cargo?  If so, it is possible to get the drive shaft sloping down forward and pass drive box oil forward.

Based on your low gearbox volume it would seem you have lost the gearbox output shaft seal.  On the later Tonti bikes it can be replaced in situ.  Can't say I remember if you can do the same on a loopframe.   Frame crossmembers in the way????

I have heard of people using a syringe under the lip of the bellows boot to fill the boot in an effort to help lubricate the Cardan u-joint and carrier bearing.  But it seems that this has been your moto for awhile and you'd know if that were done.

Patrick Hayes
Fremont CA

[lazlokovacs]

sorry, what I meant was, u joint is not flopping about or obviously broken. I agree that perhaps I should take a closer look

mechanics stethescope while turning rear wheel revealed not too much... maybe some rattle from the transmission??

don't think it was rear drive oil migrating forwards, but will measure rear drive to be sure.

[smdl]

Not an answer to your problem, but u-joint failure on a loop is usually felt as a rhythmic vibration through the right side footpeg or footboard. Ask me how I know.   

Best of luck.
Shaun

[Tom H]

So you have a good amount of oil in the u joint boot. Some options for that:

A leaky rear trans seal. Relatively easy fix.

A noise and a leaky rear trans seal. A bad output shaft bearing allowing the shaft to flop around.

A noise could be a  bad swing arm carrier bearing and a leaky rear trans seal.

I rode my 5 speed until it started having an issue shifting one day. Rode it again and really had issues shifting. Up until this it had been shifting smooth as usual. Turned out being a output shaft bearing that had failed an ate it's way through the area that the bearing was mounted in. Never felt a problem until it failed.

Sorry for the possible bad news. I hope it's something simple!!

FWIW: I have never had a DRY u joint boot. Always just a bit of oil. or maybe a bit more if there was a problem.

Look at all the simple stuff first. Like IS the center stand banging as you pull out of the driveway? When does the noise always happen?
Tom

[Rod]

I’m following this because I also have noticed a scraping crunchy sound coming from my 74 Eldo drive train, mostly when I’m coasting at very slow speed clutch in that I notice it. Once up to speed everything sounds fine. I was going to put it up on the stand or maybe my lift and try and reproduce. Noticed Patrick s warning about not putting into gear under power. How come?

[lazlokovacs]

stresses the u joint!

[lazlokovacs]

plot thickens

200cc in the rear drive

I'd always understood it needed 300 but greg bender's site says specifications vary!!!

Guzzis.....

[lazlokovacs]

I replaced the tranny and rear drive with correct oils and took a gentle test ride, as yet no noises.

Anyone want to chime in with a definitive way to test/check the u joint?

[Lannis]

Loop Gurus ... I like that!

"Loup-Garou" is French for "werewolf" ... I thought there was something strange about those loop experts!!

Lannis

[Antietam Classic Cycle]

I replaced the tranny and rear drive with correct oils and took a gentle test ride, as yet no noises.

Anyone want to chime in with a definitive way to test/check the u joint?

Remove it from the bike, grab the ends - one in each hand, attempt to twist back and forth. Shouldn't be any play - crosses in the caps or caps in the yokes. Should move easily, but not too easily.

[lazlokovacs]

changed the oils and did a gentle 100 miles of freeways today and no strange noises.

I'll keep on riding and let you know if anything goes wrong

thanks for the input everyone