How to change motorcycle primary and transmission oil

To change motorcycle primary and transmission oil, warm the bike up, drain each compartment through its own drain plug, clean the magnetic plugs, refill each with the specified amount of lubricant through the clutch inspection cover (primary) and the dipstick hole (transmission), then check both levels the way your manual describes. On Harley-Davidson big twins, the engine, primary and transmission are three separate oil compartments, so an "oil change" that only drains the engine leaves two of them untouched. This guide covers the full job and the details that trip people up.

Specs below come from Harley-Davidson service procedures for specific years. Capacities and torque values vary by model and year, so confirm yours in the service manual before you start.

Which bikes have separate primary and transmission oil?

Most Japanese and European motorcycles use one oil for the engine, clutch and gearbox. Harley-Davidson big twins (Touring, Softail and older Dyna models) are different:

Compartment	What it lubricates	Where you fill it
Engine	Crank, pistons, valvetrain	Oil tank or engine filler
Primary chaincase	Primary chain, clutch, compensator	Clutch inspection cover on the left side
Transmission	Gears and shafts	Dipstick/filler plug, usually on the right or top of the gearbox

Sportsters and Buell XB models share a single compartment for primary and transmission, so they have one drain plug and one fill point for both. If you aren't sure which layout you have, check the service manual or ask a Harley-Davidson repair shop.

Tools and supplies

• Drain pan (two if you want to inspect each fluid separately)
• Sockets and hex bits for drain plugs and the clutch inspection cover screws
• Torque wrench that reads in inch-pounds and foot-pounds
• Funnel with a long, narrow spout
• The specified lubricant (Harley-Davidson specifies its own transmission and primary chaincase lubricant, or a synthetic, depending on model)
• New drain plug O-rings and a new clutch inspection cover seal or gasket
• Clean rags and brake cleaner
• Your service manual

Why the right oil matters

The primary chaincase holds a wet clutch. Oil with the wrong friction additives can make the clutch slip. The transmission needs a gear lube that holds up to high pressure between gear teeth. That's why you shouldn't simply use leftover engine oil in either compartment unless your manual says it's allowed. Our motorcycle transmission oil guide explains the differences.

How to change motorcycle primary and transmission oil

1. Warm it up and park it

Ride for a few minutes so the oil is warm and flows out more completely. Park on a level surface. Harley-Davidson's 2013 Touring procedure has you disconnect the negative battery cable before starting, to prevent an accidental start while your hands are near the drive.

2. Drain the primary

Place the pan under the primary drain plug (on the bottom of the primary cover). Remove the plug and let it drain. While it drains, remove the clutch inspection cover screws and the cover so air can get in and the fluid drains faster.

3. Inspect and refit the primary drain plug

Clean the magnet. A fine gray paste is normal. The 2013 Touring procedure says that heavy debris on the magnet means you should inspect the chaincase components. Check the O-ring and replace it if it's damaged, then reinstall the plug. Harley lists 14 to 21 ft-lbs for that model's drain plug.

4. Drain the transmission

Move the pan under the transmission drain plug. Remove the transmission dipstick/filler plug first to let air in, then remove the drain plug. Clean the magnet, check the O-ring, and reinstall. The 2007 Touring procedure gives 14 to 21 ft-lbs for its transmission drain plug.

5. Refill the primary

Pour the lubricant through the clutch inspection opening. For the 2013 Touring models, Harley-Davidson lists 38 fl oz for a normal refill, and 45 fl oz only if the primary has been fully taken apart and is dry. Older and newer models differ.

Check the level with the bike upright and level. On 2013 Touring models, the level is correct when fluid is visible along the bottom of the clutch assembly through the inspection opening.

6. Refill the transmission

Add the specified amount through the filler hole. The 2007 Touring procedure lists about 32 oz. Then check the level on the dipstick using your model's method. On the 2007 Touring, the bike sits on its jiffy stand, and you wipe the dipstick, set it in the hole without threading it, and pull it to read. The level should be between the ADD and FULL marks. Other years may differ.

7. Reinstall covers and plugs

Fit a new seal or gasket on the clutch inspection cover and tighten its screws in the sequence shown in the manual, to the listed torque (84 to 108 in-lbs on the 2013 Touring). Reinstall the transmission dipstick, checking its O-ring, and snug it to spec. These are small fasteners into aluminum, so a torque wrench matters.

8. Reconnect, start and check for leaks

Reconnect the battery, start the bike, and check every plug and cover for drips. Wipe up all spills, especially near the rear tire and brakes. Harley-Davidson's procedures warn that lubricant on tires, wheels or brakes reduces traction and can cause loss of control.

Specs at a glance (examples only)

Item	2013 Touring primary	2007 Touring transmission
Refill amount	38 fl oz (45 fl oz dry)	About 32 oz
Level check	Upright; fluid visible at bottom of clutch	On jiffy stand; dipstick between ADD and FULL
Drain plug torque	14 to 21 ft-lbs	14 to 21 ft-lbs
Cover/filler torque	Inspection cover 84 to 108 in-lbs	Filler plug 25 to 75 in-lbs

Use these only as a reference for how the numbers look. Your model's manual has the values that apply.

Mistakes to avoid

• Overfilling the primary. Harley-Davidson warns that too much primary lubricant can cause rough clutch engagement, clutch drag, incomplete disengagement and trouble finding neutral.
• Mixing up the drain plugs. Draining the engine instead of the transmission, then overfilling the transmission, is a classic mistake. Identify each plug before loosening anything.
• Reusing a torn cover seal. It will weep oil onto the floorboard and boot.
• Stripping the threads. Overtightened plugs into aluminum cases can leak or strip.
• Letting dirt in. Clean around the cover and filler before opening them.

If you also need to do the engine oil, see our motorcycle oil change guide.

Signs your primary or transmission oil needs attention

• Clutch slipping or dragging
• Hard shifting or difficulty finding neutral (see motorcycle won't shift into gear)
• Oil weeping from the clutch inspection cover or drain plugs
• Unusual whine or clunk from the drivetrain
• Large metal pieces on the drain plug magnets

Cost

Doing it yourself costs the price of lubricant plus seals, often $30 to $70. A shop typically charges a modest labor fee on top, and many bundle it with an engine oil service. Costs vary by bike, region and shop.

When to see a mechanic

Stop and get professional help if:

• You find chunks or flakes of metal on either magnet
• The clutch slips or drags after a fluid change
• The transmission is noisy, jumps out of gear or won't shift properly
• Oil keeps leaking from a cover or plug after a new seal
• You stripped or cracked a drain plug thread or cover screw

A leak that reaches the rear tire is a safety issue; see why your motorcycle is leaking oil. To find local options, browse the motorcycle repair directory.