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Three of the most popular Red Line products for V-Twin motorcycles include V-Twin Primary Case Oil, Motorcycle 80W Gear Oil with Shockproof and V-Twin Transmission Oil with Shockproof. For Sportster and Buell riders, Red Line has found Lightweight Shockproof (not shown) to be highly effective.

Lubricants are a huge topic of debate in the V-Twin world, often focused on a simple question, "Is it the best way to follow the dealer and put a motor oil in my engine, transmission, and primary case, when I could get the correct product for each application?" After all, most American V-Twins are unique in that the engine, transmission, and clutch are lubricated through three separate systems.

Most experts and educated enthusiasts will tell you not to use a motor oil in all three compartments. Just because the dealership can manage its inventory more easily with one oil type from the factory doesn't make this one product the best choice for your bike. Using a higher-quality, fully-synthetic 20W50 motor oil, a proper synthetic gear oil for the transmission, and a specific synthetic primary case gear oil optimized for the clutch and chain makes more sense for most motorcyclists looking to protect their investment and enjoy these bikes to the fullest.

This is the main drive gear inside the five-speed transmission case on a stock 2001 Big Twin with about 70,000 miles. All of the power goes from the engine to the transmission and through to the rear wheel through this gear.  Here you see blue - the sign of high heat - on the gear and wear in the center of the teeth—this bike has been running Syn 3. Much of this can be avoided by using Red Line V-Twin Transmission Oil with ShockProof.

Why is it wrong to just use motor oil in the transmission? Simply put, motor oils contain additives specific to keeping contaminants in suspension. Since transmissions don't have to deal with the byproducts of an internal combustion engine, wouldn’t you select gear oil with chemistry that is optimized for the conditions? The same goes for the primary case. It is safe to say that the problem with a compromise is that can't do any one job really well.

We are very proud of our motor oils, but Red Line's unique product known as "ShockProof" is truly a game-changer in terms of its effectiveness in a V-Twin transmission. Many Red Line fans started using this product in its automotive packaging, known as Heavy ShockProof® Gear Oil. The same product is now packaged as V-Twin Transmission Oil. By the way, it's the same fluid used in the differential of the world's best Top Fuel Dragsters.

Acting like liquid grease, this famous pink gear oil contains a suspension of solid microscopic particles as an extreme pressure agent—its unique solid dispersion cushions gear teeth to help prevent tooth wear and allows the use of lower viscosities. The fluid really isn’t that "Heavy," as it classifies as a 90W gear oil. ShockProof gear oils also cling extremely well to metal, surely a big part of its noise dampening ability and wear control. The early stock V-Twin gearboxes are not exactly famous for their smooth shifting or quiet operation! That shifting clunk at the stoplight is gone after using our V-Twin Transmission oil, verified by the massive, unsolicited comments on the Internet's most popular V-Twin sites. 

Here is that same Big Twin with 70,000 miles, a five-speed bike. See how the middle gear has wear down the center from the shifter forks? When the gear wears, it causes premature wear to the shift forks--they're hurting each other. This is what causes the rough or missed shifts and our V-Twin Trans Oil helps to fight this, big time.

However, the oil cannot prevent everything. Lugging your bike, especially a newer model, causes both noise and wear in the transmission. ShockProof gear oils can dampen noise and help gear life in the 2007-09 H-D® Cruise Drive 6-speed transmissions, for example, but its straight-cut 5th gear is quite noisy. Given that the 96-inch motor is judged by many to be under-powered when matched to its a relatively-tall 2.79:1 final drive ratio, the bike lugs in 6th yet makes all that gear noise in 5th  (helped but not prevented by V-Twin Trans Fluid). You shouldn't have to go 90mph in 6th to avoid lugging, but is sure is fun!

Aftermarket gurus point out that this is improved in the latest bikes by Harley-Davidson's move to a 103-inch engine and a more aggressive 2.87:1 final drive ratio. Harley fixed some of these issues in their latest iteration, as techs that have already taken them apart say it’s a great transmission.

In the stock H-D 5-speed transmissions from 1980 to 2006, experts report that main drive bearing races have wear issues and were machined with wide clearances that combine with its heavy shifter drum for a clunky shift. Many of these noise, wear, and shifting issues can be helped by Red Line’s V-Twin Transmission Oil with ShockProof. Boxes from the late ‘90s feature an improved design thanks to a hollow shift drum that our gear oil can still improve. Aftermarket transmissions for Evos like Baker, Jim's and others, have run very successfully on our ShockProof fluids. Many of these companies are customers.

The primary case on most American V-Twins is a separate compartment with an independent oil bath. It houses components like the clutch, primary chain, and starter ring gear. While most think about the primary case oil to control clutch slippage or chain/sprocket wear, many overlook the importance keeping the stator coil cool for longer life and reliability. Though you don't see the rotor, it's also in the bath

Remember that ShockProof is designed for wet-sump applications only, you don't want to run it through pumps, coolers, or filters. If you see how it is attracted to your gears, imagine how it could stick to the inside of a small hose that sees little pump pressure. Also, note that it's the Heavy ShockProof/V-Twin viscosity (90W) that you want to run—we haven’t see the same level of benefits from going to our 80W Motorcycle Gear Oil with ShockProof®, Lightweight, or Superlight examples.

While many here at Red Line have been riding before it was cool (Tim Kerrigan Jr. is an AHDRA Pro Fuel Champion), we were quick to get on the Buell® bandwagon, dating back to the late '90s. We like the Sportster® style engines and road racing style with an American flare. Technically, some of the engine and specifically transmission tips aren’t focused to this community so we will try to spread a bit of our knowledge here.

Our pals at Hal's Speed Shop in New Berlin, Wisconsin ( enjoy these bikes, too. Hal's have a lot of experience modifying them for drag racing, road racing, and street bikes, too. They have been a huge technical resource for Red Line over the years and back up our fantastic success with Lightweight ShockProof® (which closely replicates the slightly-lighter 80W Motorcycle Gear Oil with ShockProof®).

Owners of V-Rods or the liquid-cooled Buells (like the late, great 1126R) need to think about using the right motor oil to keep control heat, clutch wear and slippage, and gear wear. Unlike their traditional V-Twin cousins, these engines use one oil bath of 10W40, important to curtail wear on the small end of the rod and wrist pin.

Rob Schopf from Hal's reminds us that they prepped many 5-speeds in Buells and 883 for road racing, spotting accelerated wear on the main drive gear and the 5th gear on the countershaft. Lightweight ShockProof® eliminated this. Rob says, "If the fluid fixed this on the race bikes, it should keep the street-ridden bikes going for quite some time." H-D improved the design when they went to a high-contact/ fine-tooth gear patch on later bikes (versus the older, wide teeth).

Hal's reminds that the biggest performance gains comes from freeing up drag and resistance will free up power—ShockProof gear oils have the lowest coefficient of friction of anything we blend and more than most on the market. It's one step of many details to make sure your bike runs at its best.

The latest Sportster examples (2006-2009) are much improved in the gearbox department, as they no longer puff oil out the breathers. They'd better be, as its hard to check the transmission wear in later bikes—the "trap door" which you used for access is no longer around, so you have to split the cases to see inside. Important note: Red Line does not recommend running V-Twin Transmission Oil or Heavy Shockproof in a Sportster/Buell transmission. Always remember to warm up your bike before draining or changing the gear oil, since that ensures that you get the most complete flush out of the transmission. 

The good news is that getting an American V-Twin's primary case lubricated is easier than the engine or transmission, as its chain and clutch combination is served by Red Line's MTL® gear oil. MTL features the balanced friction you would need to make a synchronized shift in a car—this lack of slipperiness is a great match to a wet clutch like in a V-Twin.

We now package this fluid as V-Twin Primary Case Oil, too. This product's balanced friction and light viscosity provides excellent clutch operation with low drag for reduced power losses—the fluid is a 70W80 GL-4 gear oil, but it features the stable ester base stocks that ensure consistent film strength over a wide range of temperatures.

Simply put: Don't lug your bike if you want to keep the primary chain and clutch in order. In 2007, the 96-inch engines started coming with a spring-loaded, automatic chain tensioner. When lugged, this design can combine with the bike’s tall gear ratio to ratchet the chain too tight, causing heat-soaked parts to wear—here, we hope you’ve switched to a our Primary Case fluid.


*Harley-Davidson, H-D, Sportster, Buell, Cruise Drive  and V-Rod are registered trade marks of the Harley-Davidson Corporation.