Rear drive running hot?

stingray

Sweet Dreams
Joined
Mar 3, 2022
Messages
2,074
Location
Almost Heaven, WV
Ride
'21 Rocket 3GT
I've noticed the last few rides the rear drive unit is so hot I can't hold my hand on it but a few seconds. It has only been a few hundred miles since the annual service was done. The one where the engine was two complete quarts low of oil. Wasn't even on the dipstick. Remember that.

Anyway, today I decide to drain and inspect for shavings or anything and refill with Mobil 1 75w/90 synthetic gear lube. What came out, literally ran out was like motor oil. Kind of golden colored and very thin. There was a black smudge on the drain plug magnet but no particles. I honestly think they had put motor oil in my rear drive unit. Like a Harley, the same oil in all three holes.

Dunno, but I'm gonna ride it hard this afternoon in the 90f heat and see if it feels any different.
 
The final drive oil isn't that thick, but has that characteristic fishy smell. The smudge on the drain plug doesn't sound too alarming, but if they cleaned it (???) just a couple of hundred miles ago I wouldn't expect much, if anything, there.

Let us know how your ride went today...
 
It was still pretty hot after a short ride, 20 mile ride. The whole swingarm seems to be getting hot too.

The questions I have; Is that normal on a hot day? Would it hurt to use a heavier GL5 synthetic gear lube? Or do I have a driveshaft bearing going out?

If that is normal I can see why the spline lube cooks off.

I wish I had bought that Infrared temp gun now.
 
I wouldn't change the weight of the gear oil. It would probably cause other problems and you shouldn't have to anyway- something other than that is wrong.

I've gone through two final drives on the Roadster (unusually unlucky) due to bearing and seal failure. Although I didn't notice any excessive heat (didn't check), a bearing going out does sound like a very possible explanation. Have you removed the FD to lube the splines? If you find oil in there "dat ain't good."
 
OK, it seems awfully thin for gear lube. It is getting so hot I couldn't hold my hand too much anywhere on the swingarm out to the cantilever tail after I got home. It was a hot day but not that many miles. I've still got less than 3000 miles on the thing. It spent six months in the shop working on the dam abs.
 
Mighty Mouse said:
I have said it a number of times. My seat gets as hot as hell. I never drifted down to the swingarm though I will next time I ride. It doesn't seem right for a seat to get that hot on a 85 to 90 degree day. After a ride my eggs are sunny side down.
Click to expand...
I ordered an Infrared Temp gun to check the temperatures. I'll shoot it to see what my ass muffin is getting up to.
 
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