4L40E/5L40E/5L50E Master Rebuild Kit BMW Cadillac

This is a master rebuild kit for the GM 5L40-E, 5L50-E, and 4L40-E five-speed rear-wheel-drive and all-wheel-drive automatic transmissions. GM built this family for longitudinal, premium platforms, so you find these units under the BMW E46 325xi and 330xi, the E39 5-series, and the X5 3.0i (BMW badged them A5S 360R and A5S 390R), and under the Cadillac Catera, first-generation CTS, and the SRX and STS. The kit carries the friction clutch plates, steel plates, the full gasket set, every rubber seal and O-ring, the sealing rings, and the pan filter, so a teardown gets fresh soft parts and clutches in one box.

Open this kit when the unit is apart on the bench for a full overhaul, whether you are chasing slipping in a specific gear, a burnt-fluid smell, harsh or flared shifts, or a converter clutch code, or simply re-clutching a high-mileage core before it goes back in. Soak the new frictions in ATF before you stack them, replace the sealing rings on the drums and pump, reseal the pan with the supplied gasket, and set your clutch clearances as you build each pack.

These are longitudinal RWD/AWD units, not the transverse front-drive GM automatics, so confirm your transmission tag reads 5L40-E, 5L50-E, or 4L40-E before ordering. This is a soft-parts and friction master kit: it does not include hard parts such as drums, the pump, the valve body, or the torque converter. Reuse your good steels and hard parts, or source those separately if a pack shows heat damage. Ships from the USA; handling in 1-2 business days.