...well, I already knew that. Here's to all the naysayers over the years who've said running gear oil was stupid or not the right application. The motor company has their own synthetic gear oil now. Take a peak at the "fitment" tab.

https://www.harley-davidson.com/stor...hetic-gear-oil

For extreme temperature environments, no doubt because it's the heavier 80W-140 viscosity. I think 75W-90 is the better choice 99% of the time, but some of the big twins in the desert heat, and maybe even the Sportsters in the desert could make use of the heavier weight gear oil and benefit.

 

Nice. I've been using Mobil 1 75w - 90w Gear Oil since my 1st Sporty. It works.

 

https://twinpower-usa.com/amfilerati...ad/file_id/22/

"THE USE OF SYNTHETICS IS NOT RECOMMENDED AS THEY TEND TO CAUSE SLIPPAGE."

Anyone care to comment?

 

Energy One (who may make the Twin Power kit) says the same thing. Doesn't slip on mine. I had heard that they only had issues with SYN3 and since they can't legally call out specifically that oil and test every oil on the market they just said no synthetics. 70k-ish miles on my E1 kit with synthetic and no slipping.

 

Hey Scuba,

I've never tried the gear oil, simply because it seems it would cause a really draggy clutch in cold weather. Are you running the 75W-90 in cold weather with no issues?

TIA

 

I use Red Line 75W90 GL5 in my Sportster. I've used it with the stock clutch, an energy one clutch and now a Barnett clutch. I have had no issues at all. No slipping, really good lock up and shifts really great. Ive got 20 thousand miles of no problems. I don't plan to use any thing else. Some have over a 100 thousand miles. with no issues. Red Line recommends it.

 

Gone through 3 clutches and no problem, then why more than one?.............trying to understand.

 

Changed from stock to an energy one when I installed a Hammer kit that put me at 110 HP. The Energy one had a bad habit of squealing on take off no matter what oil is used. The Barnett clutch fixed the squealing problem. None of this was an oil issue.

 

As a layman using a low viscosity out of spec oil compared to the synthetic gear oils folk are using might have been the issue.

 

SYN3 is a 20W50 oil. Engine oil and gear oil are measured different. It is the same viscosity as gear oil 75W90.