Blown Final Drive

[redneksoldier]

If it wasn't for bad luck, I'd have none at all. Out riding a few days ago. Cruising about 40mph or so and I hear this loud ratcheting sound followed by a clank. I felt the vibration in the foot pegs associated with the sound. I pulled over quickly and began checking out the bike. Could not find anything wrong so I continued on with no more unusual noises or vibrations. Got home and parked the bike and it sat for a couple of days. Yesterday I was getting ready to leave for work and rolled the bike out of the shop. As I rolled it back I could hear a faint ?clunk-clunk, clunk-clunk? and then the bike locked in place. Shit, now I have to waste a warm day driving my gas guzzler. Still not knowing what was going with the bike was bothering me all day. As soon as I got home last night I went out to the shop and put it on the lift for diagnosis. I suspected final drive, drive shaft, u joint, or gearbox was at fault. I pulled the plug on the final drive and a few little metal chunks fell out into the drain pan and the drain plug magnet was covered in shards of steel both large and small. Very little oil came out and it was very sparkly and chunky. Cool, problem found. Just have to rob the one off of the currently crippled '93 and will be up and riding again. So I did, and as far as I can tell all is well with the bike. I will be doing a shakedown on the way to work this morning. My real question is: where the hell did all the oil go? It never leaked a drop and was full the last time I checked it a couple months ago. Anyone else ever had or heard of this problem?

 

[dannymax]

Could it have worked thru a bad seal into the driveshaft tube?

 

[one2dmax]

It could leak into the swingarm but usually will find the way out of there too. It can also leak into the wheel if the seal failed on that side.

 

[Fire-medic]

Seen this guy around? Mod Monkeys like gear oil!

 

[dannymax]

Seen this guy around? Mod Monkeys like gear oil!

That sick little basterd!!! He's buggering the cat :surprise:.....gah-dam, they will stop at nothing to satisfy thier sick desires!!

 

[fmcandrew]

Ride-em Mod Monkey!!! Way too f'ing funny!!!

 

[Redbone]

Poor kitty! I don't even want to know what it's plan is for that straw!
:hmmm:Maybe he's been snorting the gear oil outta RNS's final drive!:rofl_200:
Stoopid primate!

 

[dannymax]

Stoopid.....STOOPID primate!! :rofl_200::rofl_200::rofl_200:

 

[95spfldmax]

It could leak into the swingarm but usually will find the way out of there too. It can also leak into the wheel if the seal failed on that side.

Do you find that the seal fails and drains the oil taking out the gears? Or the other way around where the gears fail and all the shrapnal takes out the seal at the end? Prob the first senario I would guess?

 

[one2dmax]

Lack of fluid will be what takes out the diff.

 

[redneksoldier]

I'm going with the ” mod monkey snorted it” theory. No sign of leaks and fluid was full when I checked at my last motor oil change. Definitely didn't drain out 6oz last night though.

 

[twistedmax]

So, that eff'in MM has resorted to Sabotage................thats ok as long as he sticks to two things : one, cut up stock seats , and two dont let me catch you near my garage!

 

[Fire-medic]

So, that eff'in MM has resorted to Sabotage................thats ok as long as he sticks to two things : one, cut up stock seats , and two dont let me catch you near my garage!

Um, "twisted?" Be careful, be very careful... check your awards, and prepare to

RUNNNNN!!!!!!!!!

 

[redneksoldier]

The way I see it, I have just been provided a great learning opportunity. Now that this drive is broken, I can dissect it without fear of making it unusable. Just a thought, but I wonder if the bike having been lowered plus riding double had anything to do with it. I mean, as the suspension travels upward, the drive shaft spline travels inward effectively shortening the shaft? Or is it the opposite?

 

[Miles Long]

The way I see it, I have just been provided a great learning opportunity. Now that this drive is broken, I can dissect it without fear of making it unusable. Just a thought, but I wonder if the bike having been lowered plus riding double had anything to do with it. I mean, as the suspension travels upward, the drive shaft spline travels inward effectively shortening the shaft? Or is it the opposite?

Great question!
My guess would be that because the angle between the swingarm and the upper shock mount is less than 90 degrees, shorter shocks would tend to compress the length of the driveshaft ( moving it farther into the splines of the gear coupling and the u-joint).
However, I'm sure that axial movement tolerance has been incorporated into the basic design, by the effective useable spline lengths, and the use of the compression spring between the pinion nut and the outboard end of the driveshaft. But how much tolerance? That would be a question for the design engineers.
It will be interesting to find out the root cause of your pumpkin failure, after you find the time to strip it down.
Cheers!

 

[PATMAX]

So, you're gonna make a Jack O lantern out of your broken pumpkin. Creative!
I can powdercoat it orange when you are done. Maybe it's just the ring gear though so don't trash it just to learn. But if the pinion is trashed too, I'd turn it into a science project.

 

[Redbone]

Sean mentioned that it could leak into the swingarm so it may be the shaft seal thats bad. Shorter shocks and two up riding would have the swingarm level or angled forward giving the oil a place to go. I will stay tuned to see what you end up discovering RNS.

 

[Rusty McNeil]

I cannot imagine any leak that would lose that oil that wouldn't be noticed. It be all over the wheel and diff or else running out the boot where the u joint is.

If I even put to much grease on the hub splined it ends up all over the wheel.

 

[[email protected]]

The way I see it, I have just been provided a great learning opportunity. Now that this drive is broken, I can dissect it without fear of making it unusable. Just a thought, but I wonder if the bike having been lowered plus riding double had anything to do with it. I mean, as the suspension travels upward, the drive shaft spline travels inward effectively shortening the shaft? Or is it the opposite?

Opening it up to take a look is pretty easy. If you plan to remove the pinion gear you may want to invest in a 2-3/5" hub socket to remove the pinion bearing retainer. I had the file the teeth on the socket a bit to get it to fit. Nothing major. The retainer has left hand threads
http://www.vmaxforum.net/attachment.php?attachmentid=27174&d=1332424831


Other than that, there is not much to it. I found that mounting the differential on a metal plate and then clamping the plate in a vise made the job much easier. I should have gone with something a bit more substantial but, it worked.

 

[redneksoldier]

If the shaft engages father into the splines the lower the biker goes, if you run out of splines then the shaft will butt up against the u-joint and the pinion gear and impact both with a fair amount of force when you hit bumps (our roads suck here in Tulsa). I have seen this happen on some off road rigs with improperly measured, custom shafts. Ths would definitely happen if the engineers did not plan for the bike to be lowered. I will be checking into this further this weekend. Thanks for the tips Mab. Excellent info. More to follow...