Final drive blowing fluid out vent

wilbur-t

Top Fuel
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Mar 8, 2006
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Carthage N.C. U.S.A.
Anybody had this happen? I saw a little trail from the vent on the final drive the other day. I wiped it off and checked fluid level, it was ok. Got home from work yesterday and there was a pretty good trail of fluid from the vent. I changed it last about 4k miles ago with a full syn. gear oil. I don't remember the weight.
 
Wilbur.....

It's either overfilled or, very rarely you have a seal problem and the only way to check if it's a seal problem is to loosen the companion flange hex nuts and see if any oil weps from the flange. If it does, the seal(s) at the TDU end are leaking and that will require a teardown.

I believe it's slightly overfilled. It is touchy about volume. I changed mine and it weeped a bit as well. Probably got changed again at Baxter's.
 
Be SURE it's not leaking. We had a guy blow the rear out of his R3 at well over 100mph. Still don't know how he kept it upright. His "tell-tail" was similar to what you report.
 
I changed the fluid again last night. Used Valvoline Syn Power 75-90 fluid. I think I may have used 75-140 last time, which is the synthetic lube we keep at the shop. Maybe that is too thick? Anyway, didn't see anything bad in the old fluid, so I'll watch it close. If it weeps any more, I'll loosen the mounting bolts and check it. Thanks Guys.
 
KingOfFleece said:
It's gotta be GL-5 rated or no good to use.
Click to expand...

All synthetics are GL5. What you don't want is a GL6. GL6 rated gear lube is actually a combination of GL4 and 5.

The shop manual actually calls out Mobilube SHC 75W-90 fully synthetic hypoid oil or equivalent and NO GL rating whatsoever. I used Shell 85-90 Synthetic Gear Lube last time I changed mine. It only holds 0.17 Liter which is a little more than 3 ounces. Not much and it's easy to overfill.

The only way you could destroy the final drive is run it dry and it's easy to check anytime. Just place the back of your wrist on the housing after you've ridden the bike 15 miles or everythim you stop for gasoline. If you can keep the back of your hand on the housing, it's running cool enough and has oil. If you can't you better pull the plug and see where the level is at.

Because the housing holds so little lube, any external leakage is cause to look at the level.
 
Warning Will Robinson....

I have heard of the seal between the final drive and the drive shaft going out and engine oil fills up the final drive unit??? The only way you know is oil comes out the vent. It may be that compression from the crankcase is adding to this (kind of like using the final drive as an engine breather). In fact... wasn't the final drive recall on the earlies because of this seal failure?

That final drive takes almost no lube at all. You should look it up but it is some stupid small amount, like 3 or 4 ounces. I change mine every spring whether it needs it or not. Careful with the drain plug, it is very easy to strip when you tighten it.
 

We know that if the TDU bearing is passing that much oil, it will never go bad.

That's why I said to crack the hex nuts on the companion flange between the final drive casting and the drive shaft housing and see if any oil weeps out....a sure sign of a good breathing seal.

Look at it this way...additional oil capacity.

Isn't the final drive unit made by Maserati or Ferrari or something like that?? Maybe it was Lambroghini. We know it wasn't Chrysler for sure........
 
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