How hot does your rear drive get?

[luthier]

I need to know for my Ambo which is getting hot after 20K's or so. I can still touch it but it's hot.
I don't like this. If a brake was this hot you'd say it was binding.
Opinions please.

[Kiwi_Roy]

Perhaps just slide a piece of card in between the drive and the wheel to make sure there's enough clearance.
I don't know why mine was rubbing but it was a replacement from fleabay, the original pinion was absolutely trashed.

I suspect at one time it was getting so hot all the oil was blown up into the driveshaft area to run back as it cooled. I first noticed a drip around the rubber boot over
the universal, since I shimmed it out no more heat.

[Triple Jim]

My Mille's rear gearbox gets hot enough that I can't keep my hand on it if I've been riding 60 mph for a hour or so.  Nothing is rubbing, the oil is clean when I change it, etc..

[Antietam Classic Cycle]

As I posted in your other thread, just out of curiosity, I've been using my infrared thermometer to check the operating temperature of the rear drives on various Guzzis here. All of them fall into the 110*F to 160*F range. This includes two that have been reshimmed by Charley Cole, one that was just done by Sean Fader and one on a LM3 that has 30k miles on it from the factory. 

[normzone]

Much thanks for that empirical data. I'm assuming that's well within the manufacturer's approved operating range for the oils involved.

[luthier]

That's really helpful thanks Charlie.
I'll get one of those thermometers from our local auto store to be sure, but I'd say it's probably in that range.
Still seems too hot but if they all do it I can relax as they all mostly keep going for a very long time.

[Triple Jim]

If a rear gearbox loses just one horsepower to friction, it's like having a 746 watt heater inside it.  I have a v-drive drag boat.  The gearbox has only two simple gears in it, but it has a water jacket for cooling.  When it's used in an oval course racing application, you need to plumb water to it to keep it from overheating.

[garbln]

I posted with the same basic question a while ago.  The impression I got from the reply's was that they tend to run on the hotter side.  My 70 has the smaller case so that may tend to raise the temp a few degrees from the later cases.  I pulled mine apart, checked everything, replaced the seals and gaskets and buttoned it all up without changing anything else.  I put Lucas gear lube and a few oz. of Moly in and quit worrying about it.  I now have a 2K Mi on it since then.  I still think it runs a bit hot, hotter than my BMW gears but it seems to be stable and works fine.  It seems to be happy the way it is, it may even be a little bit cooler now. 

[drburt]

2001 EV.
Just rebuilt the rear drive 300 miles ago.
Inner/outer seals, needle bearings with inner/outer races, large ball bearings, etc.
Just ran 15 miles @ around 80MPH and had 144 deg on bottom of rear drive in about 70 degree weather.
Used Moto Guzzi Final Drive Lube (with premixed moly) from Harpers.
FYI

Brent

[Triple Jim]

I still think it runs a bit hot, hotter than my BMW gears but it seems to be stable and works fine.

Yes, I went on a big loop that included the Cherohala Skyway a year or so ago, and one of the other riders was on his late model BMW.  At one of our stops, I felt both our rear gearboxes, and his was definitely cooler.  I assume it was a different gear design that causes less friction loss in the BMW gearbox, compared to my 25 year old Mille's gearbox.

[Dofin]

my 2015 V7 stone checks at about 150 deg + - a bit on normal 80 deg days during fun back road runs.  Usually checks the same temp on the interstate trips.  My Honda PC800 checks 165 when I am towing my trailer.

[Curtis Harper]

I have always wondered what prompts people to do this. Not being crass here, but just standing on the other side of the question. How many people drive there RWD car or truck 100 miles and jump out, crawl under the back of it and try to lay their hand on the rear diff?

I generally can't put my hand on a hot asphalt parking lot in July in Missouri, so I just don't do it.

Curious to the reasoning.

[Chuck in Indiana]

I have always wondered what prompts people to do this. Not being crass here, but just standing on the other side of the question. How many people drive there RWD car or truck 100 miles and jump out, crawl under the back of it and try to lay their hand on the rear diff?

I generally can't put my hand on a hot asphalt parking lot in July in Missouri, so I just don't do it.

Curious to the reasoning.

Well, Luthier has just put this bike together with parts from all over the world. I think I would check things after riding it a bit and wonder, "is this normal?" if I didn't know..

[Triple Jim]

Curious to the reasoning.

For me it was curiosity.  I'm an engineer, and wondered about the amount of power loss in the rear drive.