Synthetic Oil

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Design and content © 2004
Mild Bill (Asshole #27)
StephG (Asshole#108)

Revisions/updates  2006 Keeper of the FAQ's
Schmoe (Asshole #128)

r.m.h VB&G logo design © Jim Combs


Tranny Lube

Chris deHahn writes:

"My experience with gear lubes is limited to the testing I did with my stroker. It was not a lab test, it was an application test. It proved to me, beyond a shadow of a doubt, that the type of gear lube used in a Harley-Davidson transmission has a profound affect on it's performance.

HD semi synthetic -- good all around, got sloppy when hot
Golden Spectro 80W -- too thin, shifted poorly throughout heat range
Bel-Ray 90W -- much better, but not as good when hot
Bel-Ray 80W-140 -- as good as it gets, shifts quick and clean cold or hot

This was a Big Twin four speed tranny with Andrews CR gears, clutches, shafts, and forks, with a ~110hp Shovelhead stroker motor driving it."



Today, all Screaming Eagle OEM Harleys are delivered from the dealer with H-D Syn-3 in the crankcase, tranny & primary. For years, the motor company advised against using synthetic lubrication. When they discovered that customers would pay $3-4 more for a  quart of synthetic, the benefits quickly out weighed the negatives and H-D became a synth advocate for their brand product. Many in the group now use synthetic lubricant (Syn-3, Mobil-1 etc...) rather than type specific transmission fluid and some report smoother shifting. Most owners who are doing this own TC-88 engines but I'm sure there are a few Evo's with synth in their transmission these days. A google of rmh will turn up multiple on-topic discussions. Don't start one unless you've truly got something new to add. It's among the most overly posted newbie mistakes along with helmet and waiving threads.