Best Transmission Oil for Harley-Davidson: Protect Your Gearbox

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If you are not quite sure whether it is time to change your Harley transmission oil, simply enter your model’s VIN on the official H-D service info site and get the official Instruction Sheet. In its Basic RiderCourse Handbook, Motorcycle Safety Foundation insists on checking the oil level before your every ride.

Top Pick
Spectro Oil R.HDPG6 Heavy Duty Platinum Full Synthetic 6spd...
Uses unique G4 Technology for gear protection
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Budget Choice
Red Line (42904) V-Twin Primary Case Oil - Engine Oil (1...
Cleans the engine
My preview
Premium Choice
Mobil (112812-4PK) Delvac Synthetic Transmission Fluid 50 -...
Helps with fuel economy
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And, once your Harley transmission fluid needs to be replaced, check our list to get the most appropriate oil (synthetic or mineral-based) to serve your bike effectively under any weather conditions and temperatures. Protect your Harley-Davidson’s gear using the best transmission oil for Harley-Davidson and enjoy a comfortable ride longer with our Harley gear oil recommendations.

Top 5 Best Transmission Oil for Harley-Davidson

All the brands of transmission oil listed below are perfectly suited for Harley-Davidson bikes. They do not void the warranty and meet all the HD requirements.

1. Spectro Oil Heavy Duty Platinum — Best Transmission Oil for Harley-Davidson

If you like riding frequently, and your routine trip is many miles long, Spectro Oil will be ideal for you, as it functions perfectly under heavy load and pressure. You will forget about cold weather transmission problems and issues with shifting gears and never stop enjoying the freedom of adventure.

This synthetic Spectro oil allows your transmission to work for miles before you have to refill it. Its unique G4 Technology and special additives create the proprietary formula that covers gears with a film that protects them and makes gear shifting exceptionally smooth. G4 Technology additionally provides anti-wear protection and more quiet transmission.

5th gear often irritates experienced riders with its noise, and Spectro Oil Heavy Duty Platinum readily eliminates the clunking and whining sounds. And the owners of the fantastic but loud 6-speed transmission would also appreciate this oil for its noise reduction properties.

It’s good news that Spectro Oil Heavy Duty Platinum is warranty-friendly to your Harley-Davidson. Even though this oil is not multifunctional and costly, it is still the best all-weather, smooth-shifting transmission oil for Harley-Davidson in 2020!

Spectro Oil R.HDPG6 Heavy Duty Platinum Full Synthetic 6spd...
  • Cures noisy six speed transmissions
  • Smoother shifting, reduces fifth gear whine and eliminates clunks
  • G4 technology, special additives that provide additional anti-wear protection, higher film strength between the gears, and reduces drag while extending gear life
  • High loads and extreme heat do not affect the oil
  • A.P.I. Gl-5 rated. Dyed Red. Exceeds all known OEM and Harley Davidson warranty requirements
  • Performs well under extreme load and high pressure;
  • Stays effective for many miles due to high viscosity;
  • Uses unique G4 Technology for gear protection;
  • Meets the HD warranty requirements;
  • Significantly reduces Harley’s 6-speed noise.
  • It’s a bit challenging to find it in retail.

2. Red Line V-Twin Transmission Oil — Harley Sportster Transmission Oil

Red Line 42904

How do you feel about listening to the gearbox noises when riding a sportbike? It can drive a person mad, and the main factor that affects it is transmission oil. The fluid cannot withstand the pressure of the gear teeth as they shift. And, when you have a Sportster by Harley-Davidson, this problem seems even more frustrating.

But the solution is easy; all you need to do is switch to Red Line V-Twin Transmission Oil. Its friction modifiers substantially dampen the gearbox sounds, that is why Red Line producers marked its oil bottle with a “shockproof” title. The Red Line oil’s high viscosity allows it to cover every gear tooth with a thick layer and, thus, protect it from wear and tear.

Especially true for sports bikes, engine overheating is a serious problem that can hamper your riding performance and, eventually, damage the engine itself. The synthetic transmission oil by Red Line prevents the transmission fluid temperature from growing too quickly and extends the life of your engine. Also, the oil accumulates dirt as it flows within the engine, cleaning it and preventing the dirt from clumping together.

You will not have to worry about the warranty issues as Red Line V-Twin Transmission Oil meets all the HD requirements. This Harley-Davidson transmission oil specifications allow it to be used in all Harley-Davidson transmissions, including Twin Cam and Evolution engines, as well as the recent Cruise Drive with its 6-speed transmission. The noticeable pink color of the liquid is useful in the case of leakage.

Red Line (42904) V-Twin Primary Case Oil - Engine Oil (1...
  • Item Package Height:22.86 Centimeters
  • Item Package Length:9.906 Centimeters
  • Item Package Width:12.446 Centimeters
  • Country Of Origin: China
  • Product Type:Auto Oil
  • Reduces the noise of the gearbox;
  • Has a bright pink color;
  • Its high viscosity protects gear teeth;
  • Cleans the engine;
  • Prevents gearbox from overheating.
  • Some riders reported the smell of the burning oil.

3. Mobil Delvac Synthetic Transmission Fluid 50 — Harley Transmission Fluid with High Viscosity Index

Mobil 112812-4PK Oil

Having a viscosity index of 146, this fully synthetic oil by Mobil brand supports shear stability. It keeps its viscous properties even under high temperatures and heavy-duty conditions. Therefore, this Harley Transmission oil weight is exceptional for your off-road tracks and adventures.

With this transmission fluid, you can save on your fuel and extend the functional life of your Harley’s components. Mobil Delvac Synthetic Transmission Fluid 50 also works great at low temperatures and allows starting quickly due to improved shifting.

The Mobil Delvac oil is compatible with GL1 to GL-4 gears, which means it cannot be used for your 6-speed HD, which requires the GL-5 oil. The difference between the two is in the quantity of EP (extreme pressure) additives and, the higher the EP, the greater the GL is.

For instance, GL-5 has twice as many EP additives when compared to the GL-4; that is why it is crucial to follow the manufacturer recommendations based on the pressure, temperature, and riding conditions. This oil meets the original equipment manufacturer (OEM) warranty and can be used for your Harley-Davidson bike with no warranty voiding.

Mobil (112812-4PK) Delvac Synthetic Transmission Fluid 50 -...
  • Excellent load carrying, anti-wear, and EP performance
  • Outstanding protection against deposit formation
  • Maximum protection from corrosion of copper and its alloys
  • Optimized thermal and oxidation protection
  • Exceptional shear stability
  • Has a high viscosity index;
  • Reliable in extreme operational conditions;
  • Helps with fuel economy;
  • Meets warranty requirements.
  • It cannot be used for your new HD 6 speed.

4. Maxima Racing Oil V-Twin Transmission — Best Transmission Oil for Harley 6 Speed

Maxima Racing Oils 40-01901

Harley-Davidson manufacturers understand that its Harley riders may not always find the dealers to buy genuine transmission oil. For such cases, the HD manual gives recommendations for the oils that are acceptable for use. This way, you can use the HD transmission oil equivalent without damaging your transmission or voiding your warranty. The formula providing high performance is exceptional for extreme riding conditions your Harley often faces.

Without a doubt, you can use Maxima Racing Oil for your HD, including the 6-speed Harley transmission, as this mineral-based oil for motorcycles generates a film on the gearbox parts and works ideally under extreme loads on your transmission during racing. However, you will need to change this mineral-based oil more often than its fully synthetic equivalents, which may result in greater costs.

The additives that protect the gear from the high pressure and chemicals that cover the transmission elements’ surface make the shifting softer and less noisy at shock loads. This Harley-Davidson transmission oil capacity allows you to ride on your bike non-stop for many miles.

Maxima Racing Oils 40-01901 85w140 V-Twin Transmission/Gear...
  • Maxima V-Twin Heavy-Duty Transmission & Gear Oil is a high-quality, mineral based motorcycle gear oil
  • Recommended for use in 4-, 5- and 6-speed high performance gear boxes
  • High film strength gear oil provides excellent protection against shock loads, viscosity loss and wear
  • Extreme pressure additives and surface active chemistry allow smooth shifting under peak loads and RPMs
  • Ultra-clean detergents protect gears from wear, deposits and allow for trouble-free operation
  • Can be used in a 6-speed gearbox;
  • Smooth gear shifting at high loads;
  • Protects against heavy loads and wear;
  • Includes detergents.
  • Mineral-based oil needs to be changed more frequently.

5. Bel-Ray Big Twin Gear Oil — Harley-Davidson Transmission Oil Equivalent

Bel-Ray Oil 96900-BT1

This manufacturer guarantees to make the gear shifting process smooth and even promises to increase your Harley’s power! This oil almost completely eliminates the sliding friction, allowing your bike’s motor to work better than it ever did before.

The chemical additives used in this Bel-Ray oil give superior shock protection to the most sensitive parts and decrease the friction, unlike almost all other oils on the market. This fluid protects the transmission from oxidation by creating a film of oil that retains its properties even under high temperatures.

Bel-Ray Big Twin Transmission Oil was created for Harley-Davidson’s V-Twin Engines. These engines’ transmissions require hypoid oils. The viscosity of the Bel-Ray oil helps to avoid (or at least minimize) the breakdown effect of the gear shearing. This Bel-Ray oil’s distinct red color makes it noticeable when it leaks, allowing you to notice when something is wrong immediately.

Bel-Ray 96900-BT1 Gear Oils
  • Superior lubricity minimizes sliding friction for maximum power.
  • Use in combination with Bel-Ray V-Twin Synthetic Motor Oil for maximum performance
  • Special lubricity additives provide for exceptionally smooth and quiet shifting
  • Maximizes horsepower rate;
  • Smoothens gear shifting;
  • Minimizes gear shearing;
  • Resistant to extreme temperatures.
  • Some may not like its vivid red color.

Follow the Recommendations of the Manufacturer

Before you decide to buy any Harley-Davidson transmission oil equivalent, learn the manufacturer specifications for the transmission fluid, as recommended by the Universal Technical Institute of Illinois. Please remember to avoid multifunctional oils and buy separate fluids for your motor and transmission instead.

This option will cost you more but will result in a better and longer performance of your bike. Any motorcycle transmission oil from the list above is good for your HD; however, Spectro Oil Heavy Duty Platinum is the best oil for Harley transmission that will not void the warranty!

What about your own experience with Harley transmission oil? Tell us if you have already changed it, which brand you preferred, and whether it was to your liking.

FAQ Section

Harley-Davidson Low Rider S 2020

Here is a list of the most frequent questions that people ask with regards to the Harley Davidson transmission oil change.

How many quarts does a Harley-Davidson transmission take?

The capacity of the Harley-Davidson transmission container is around 24 ounces, which equals 0.75 quarts. Harley-Davidson’s official service info site recommends avoiding leakage and not overfilling the HD transmission oil tank. It is best to go a little bit below the full mark on your bike’s transmission.

How often should I change the transmission oil in my Harley?

The service manual states that trans fluid should be changed every 20,000 miles, while primary oil should be replaced every 10,000 miles, and engine oil is renewed every 5,000 miles. The transmission oil is recommended to be changed at least once every year. However, if your riding style is hard, if you travel for long distances or weather conditions are rough, the oil change intervals may be shorter.

What kind of fluid is better for a Harley transmission?

You need to use the fluids certified by Harley-Davidson; otherwise, find the warranty compatible equivalents that meet the HD requirements. In general, the transmission oil should be resistant to significant loads, extreme pressure, and high and low temperatures. Almost any synthetic oil meets (and sometimes exceeds) the HD manufacturer’s requirements so that your warranty will not be voided. Our top 5 list above includes only those oils that can officially be used for your Harley.

Are there times when I should not use synthetic oil?

Whether you have an old or a new Harley-Davidson model, you can use synthetic oil for its transmission every time without exceptions. The synthetic fluid has several advantages over the standard one: it reduces the transmission noise, stays effective in any weather conditions (even the extreme ones), decreases the engine temperature, and serves longer. Therefore, you will change the oil less frequently.

How to check the transmission oil on Harley?

First, you need to warm up the engine, shift through every gear, and then turn it off. Unscrew the transmission dipstick (do not remove it) and leave the bike for 30 seconds. Take out the dipstick and wipe it thoroughly. Insert (but do not screw on) the dipstick until its top covers the hole and take out.

You will find the mark that shows the oil’s required level and see if your oil level is too low. Add a little bit of the fluid, put the dipstick in place, start your engine again, and switch through every gear. Repeat these actions until you reach the necessary level. It is essential not to go above the mark as it may damage your transmission.

So What’s the Best Transmission Oil for HD?

Overall, if you look for a transmission oil for your Harley Davidson, your best bet is to purchase Spectro Oil Heavy Duty Platinum. Not only does it greatly reduce the noise that is generated by Harley’s 6-speed, but it also provides high levels of protection due to its high viscosity and G4 Technology.

What are your thoughts on the transmission oils mentioned in this article? What transmission oil do you use in your Harley Davidson? Share your thoughts and comments below.

Bruce was born in Atlanta. He started riding motorcycles when he was 10 and has been passionate about them since. Bruce says he feels absolute freedom when he’s on two wheels. He prefers riding his bike slowly and smoothly along a country road and hardly ever enjoys wildly speedy rides. With a strong Ducati Multistrada 1200 in the current stable, Bruce enjoys his super powerful, comfortable and easy rides. Ducati Diavel is the beast he’s currently dreaming about...

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