I use Red line shock proof very pleased. Bike has 24,000 on it 5K with Red line so far happy with it. Smooth

 

Lucas 75-90 syn. gear oil since the 1000mi service.

Zero problems.

 

Amsoil SVT 75-110 Gear Oil.

 

I tried one change with Amsoil 20w50 in the tranny, then switched to Amsoil severe gear 75-140. The difference was night and day. It shifts a LOT smoother with the 75-140.

 

this is exactly what i did and i had the same results.

 

I use red line to. I am looking for something else. Red Line has a strong bad smell to it. It seems like the bike is smelling like Red Line.

 

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Here's what i use that's specifically designed & formulated for HD 6spd and Primary too.

Scott

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http://performanceoilstore.com/products.asp?cat=65&pg=4

Spectro Heavy Duty Platinum 6-speed Transmission Oil 1-qt. Enter quantity of 12 for case discount. Designed by Spectro in response to complaints from Harley owners about the great but noisy new 6-speed transmission, this full synthetic provides ultimate lubrication protection. Formulated to significantly reduce gear noise and provide easier, smoother shifting, this SAE 75w140 formulation eases shifting even when cold. High loads and extreme heat do not affect the oil, so it performs well when pushed hard and long. [/B][/B][/B][/B][/B]A.P.I. GL-5 rated
List Price: $19.60
Price: $15.85

http://performanceoilstore.com/products.asp?cat=65&pg=4

Spectro Heavy Duty Primary Chaincase Oil 1-qt. This sheer stable petroleum is designed to withstand the punishment of high loads, and contains special polymers to provide exceptional clutch engagement and temperature stability. Meets full OEM requirements, and should be used according to manufacturers’ instructions. Formulated specifically for Harley® Sportster and Big Twin applications. Low drag, low friction loss SAE 85w viscosity helps eliminate clutch “drag” and slipping.
List Price: $12.04
Price: $7.95

 

90 weight full syn gear oil

 

Bel-Ray Gearsaver 85/140. Changed to this at the first service and never looked back.

 

after reading this entire thread i ran into a friend yesterday and we were talking about tools. i thought he had been into his transmission before. but he hasn't. 127,000 miles on a 2000 road king running Redline. he's been though a belt and pulleys but nothing else with the trans. hard to argue with them facts.