Acura RDX (First Generation) Transfer Case Fluid Change

Work with the drivetrain cold or only mildly warm to avoid burns from hot oil. The transfer case is filled to the bottom of its port, so the vehicle must sit level for the fill amount to be correct. Lay a spirit level across the rocker panels beneath the doors and confirm side-to-side and front-to-rear are even before you begin. If you raise the RDX, do so only on level concrete and support it fully on stands; this vehicle weighs roughly 3,950 lb, so never let any part of your body under it until it is solidly secured.

The transfer unit sits at the rear, passenger-side end of the transmission. It carries two identical plugs: a fill plug that faces forward and a drain plug that points down from the bottom of the housing. Both take a 3/8-inch drive square directly, with no socket. Before touching anything, wipe the unit down and look it over; a healthy case is dirty on the outside but shows no wet oil trails.

Always break the fill plug loose before you drain anything, so you are certain you can get fresh oil back in. Fit the ratchet and a short extension to the forward-facing plug and crack it free. Remove it and look into the port: a correctly filled case sits right at the lip of the fill hole, and a little oil may weep out. Thread the fill plug back in loosely for now.

Slide a catch pan under the housing and remove the bottom drain plug. Let the case empty completely; a full change yields about 430 ml (0.45 qt). Measuring what comes out is optional and mainly serves as a check that the case was not leaking. Wait for the flow to slow to nothing before moving on.

Wipe the drain area and the surrounding housing clean so any later seepage is easy to spot on the leak check. Fit a fresh sealing washer (PN 94109-20000) to the drain plug; optionally add a little thread sealant. With a new washer, torque the drain plug to 44 N-m (33 ft-lb), which lightly crushes the washer. If you are reusing a washer, do not use the full torque figure: run the plug down to contact, then turn only another 30 to 45 degrees (up to an eighth of a turn) to seal it, and nip it tighter later only if it seeps.

Thread your pump onto the gear-oil bottle and seat the hose fitting into the fill port. Pump the oil in slowly, watching the sight scale on the bottle; the target is 430 ml (0.45 qt), which brings the level to the bottom of the fill hole. The factory manual describes the same endpoint as filling until oil just begins to escape the port, so stop feeding oil once it reaches the lip and starts to trickle back out. Keep a container underneath to catch the overflow.

Once the fluid slows to a trickle at the port, fit the fill plug with its washer and torque it to 44 N-m (33 ft-lb), or use the reduced reused-washer method if the washer is not new. Wipe every surface dry and clear away your tools and rags so the underside of the drivetrain is spotless for the final inspection.

Lower the vehicle and take a short drive to bring the fluid up to operating temperature. Return, look under the transfer unit, and inspect both plugs and the housing for any fresh oil. Because you cleaned everything beforehand, even a small seep will stand out. If a plug weeps, snug it slightly and recheck. A common interval for this service is roughly every 30,000 miles, done alongside the transmission fluid change.