The short answer: To change Harley-Davidson* transmission oil, remove the drain plug under the transmission between the rear shocks, fit a new O-ring and torque the plug to 14–21 ft-lb. Then remove the transmission cover with a 3/8-inch ball-end Allen wrench, refill with V-twin transmission fluid and check the level on the dipstick as your owner’s manual directs.
For maximum wear protection and shift performance, it’s important to periodically change transmission oil in your motorcycle. Otherwise, the fluid can breakdown and fail to protect gears and bearings, not to mention interfere with the smooth, crisp shifts you want when riding. Here, we provide Harley-Davidson* transmission oil change instructions using a 2014 Softtail Fat Boy Lo.
In essence, Synthetic V-Twin Transmission Fluid and Synthetic V-Twin Primary Fluid are formulated to protect just one area of your bike rather than three. This specificity allows AMSOIL to “over-engineer” each lubricant for its precise application.
Synthetic V-Twin Transmission Fluid has a higher viscosity than 20W-50 Synthetic V-Twin Motorcycle Oil. A higher-viscosity, or “thicker,” lubricant provides some advantage in helping quiet noisy transmission gears and enabling smooth shifts.
The lubricant develops a slightly thicker fluid film on gears, which provides extra cushion to help diminish loud “thunks” and gear noise.
Synthetic V-Twin Motorcycle Oil also boasts a shear-stable formulation. It resists viscosity loss despite the intense pressure and churning action of high-rpm transmission gears, allowing it to deliver reliable transmission protection.
Synthetic V-Twin Motorcycle Oil meets JASO MA/MA2 standards and is wet-clutch compatible for excellent performance in the primary chaincase. Its frictional properties are dialed-in to allow the clutch plates to engage and disengage without loading or slipping for smooth shifts.
Watch: Harley-Davidson Transmission Oil Change Instructions
Video transcript: How to Change the Transmission Fluid on a Harley-Davidson Motorcycle
Welcome to Tech Tips. I’m Len Groom. Today we’re changing the transmission fluid on a Harley* Davidson motorcycle. Let’s check in with our Trade Show Manager and in-house motorcycle enthusiast Patricia Stoll on how to do that.
It’s relatively easy to change the transmission fluid on a Harley Davidson Softail. This is a 2014 Fat Boy Lo with a 103 cubic-inch engine. You’ll need a few tools to do this project. You’ll want a drain pan, a new O ring for your drain plug, a 5/8-inch socket with a socket wrench, of course your torque wrench, a 3-inch extension, and a 3/8-inch ball-end Allen wrench, a funnel and, of course, your AMSOIL V-Twin Transmission Fluid.
First you need to locate your transmission drain plug, and it can be a bit tricky. First, locate your two shock absorbers. It’s located in between the shock absorbers underneath the transmission. Now that you’ve located your transmission drain plug, take your ratchet and your 3-inch extension and your 5/8-inch socket and remove it.
So once it gets loose enough, I like to finish removing the drain plug by hand. I do this so the drain plug doesn’t fall into the oil. So while the transmission fluid was draining, I took advantage of that time to clean my drain plug. Make sure you remove all the debris, and check it for any damage.
Now take your new O ring and slide it onto your transmission plug, and make sure you run it all the way to the bottom like that. So once you have your new O ring on your transmission plug, take your 5/8-inch socket and your 3-inch extension and reinstall your drain plug. When replacing the transmission plug, I like to snug mine up by hand. You’ll want your torque wrench set at 14 to 21 foot-pounds of torque.
I have mine set at 16. Okay. That should be good. So now that we’ve replaced our transmission plug, we’re going to fill our transmission.
I like using AMSOIL Synthetic V-Twin Transmission Fluid. Make sure you check your owner’s manual so you know how much fluid is required for your bike. So next you’ll take your 3/8-inch ball-end Allen wrench and remove your transmission cover and dipstick. This one’s a little tricky.
So now we’re going to fill our transmission with fluid. Remember you’re going to need a long-neck funnel and your transmission fluid. This Harley Davidson Softail requires 28 ounces of fluid; and, as you know, there’s 32 ounces in a quart. So when you get done filling it, you’re going to have 4 ounces left over.
And be very careful. It’s very important not to overfill your transmission. So remember to stop and check your site gauge. I’ve got about 14 ounces, so I’ve got a ways to go yet.
Okay. Make sure your bottle is level. I’m at 8 ounces. I still have 4 more ounces to go.
Okay. Check it. That’s right at about 4 ounces left. So now with this bike it’s recommended that you check your transmission fluid when it’s on the kickstand.
So I’m going to take it off the mechanic stand, back it off and do that. It’s kind of hard to see because the fluid is so clear, but our fluid levels are right where they need to be. So we’re good to go. Well, there you have it.
We’re done. As you can see, it’s not that difficult to change the transmission fluid on a Harley Davidson Softail. There you have it. Remember, for your specific capacity, check your owner’s manual; or check out our lookup guide at amsoil.com.
Thanks for watching. We’ll see you next time.
Tools you need
- Drain pan
- New drain-plug O-ring
- 5/8-inch socket with a socket wrench
- Torque wrench
- 3-inch extension
- 3/8-inch ball-end Allen wrench
- Funnel
- AMSOIL V-Twin Transmission Fluid
- Locate the transmission drain plug, which can be a bit tricky. First, locate the two shock absorbers. The drain plug is located between the shock absorbers, underneath the transmission.
- Use the ratchet, 3-inch extension and 5/8-inch socket to remove it. Once it’s loose, finish removing the drain plug by hand to prevent it from falling into the drain pan.
- While the transmission fluid is draining, clean the drain plug. Make sure to remove all the debris and check the plug for damage.
Install a new O-ring
- Slide the new O-ring onto the transmission plug and run it all the way to the bottom. Re-install the drain plug. Snug it up by hand, then use the torque wrench set at 14-21 foot-pounds torque to tighten it.
- Use the 3/8-inch ball-end Allen wrench to remove the transmission cover and dipstick. Use a long-necked funnel to install the transmission fluid. Be careful not to overfill the transmission. Check your owner’s manual or the AMSOIL Product Guide for the correct fluid capacity. Remember to stop and check the site gauge on the bottle to prevent adding too much fluid.
- Some bikes require checking transmission fluid when it’s on the kickstand. Check your owner’s manual for specific instructions for your bike, then pull the dipstick and verify the fluid level.
There you have it – Harley-Davidson transmission oil change instructions for your next oil change. Make sure you dispose of the used oil properly.
Check out our posts on how to change oil on a Harley-Davidson and how to change primary fluid on a Harley-Davidson.
This article is part of our Motorcycle Oil and Maintenance guide. See every article in the guide.