U660F Clutch Drum 2010

All-wheel-drive V6 Toyota and Lexus models built with the U660F six-speed put a lot of load through one part: the forward and direct clutch drum. When an AWD Highlander, RAV4 V6, Sienna or RX350 starts slipping on takeoff, flares when it reaches fifth, or will not pull forward at all while Reverse still works, this drum is high on the list. What you get here is the late-style drum for 2010 and newer U660F units, remanufactured and fully loaded. The listing states it includes new forward and direct friction plates, new steels, and new forward and direct pistons with their retainer, already assembled on the input shaft.

How the forward/direct drum works in a U660F

The U660F is the AWD member of the U660 family; it adds a transfer drive to the rear axle but shares the clutch layout of the front-drive U660E. ATSG's U660E information shows two driving clutches. C1, the forward clutch, holds in first, second, third and fourth. C2, the direct clutch, holds in fourth, fifth and sixth. In fourth both are applied, which locks the gear train for a direct ratio. Fluid reaches the two pistons through sealing rings on the drum's input shaft, which is driven by the torque converter turbine. On an AWD vehicle the drum feeds both axles, so a heavier vehicle, a trailer or a long grade will find a weak pack faster than a light front-drive sedan. The listing gives the assembly as four forward clutches and three direct clutches, with a shaft roughly 9 1/4 inches tall.

Signs the drum is failing

• Engine flares on launch or under load in the lower four gears
• Fifth and sixth slip or the 4-5 upshift runs long
• Drive is lost entirely but Reverse still pulls
• Dark, burnt-smelling fluid with friction debris on the pan magnets
• Slip or ratio codes stored after highway or towing use

Diagnose before you order

Scan every module first and fix engine-side faults; Gears Magazine notes that a dirty throttle body or slow MAF sensor can make these units downshift harshly with no transmission fault at all. Verify the WS fluid level hot at the overflow plug. Then use a gauge. ATSG's case diagram shows separate test taps for the C1 and C2 clutches beside the line pressure tap. Normal pressure with a slipping clutch means the drum's seals or plates are gone. Low pressure everywhere sends you to the pump and valve body; our U660E/U760E service guide lists the valve bores that wear and drop pressure.

Fitment

This assembly is listed for the 2010-and-later U660F, with a U660E cross-reference because the late drum is shared. Toyota changed the drum during production, and there is a separate 2007-2009 U660F drum for early units. Before ordering, read the tag on your case to confirm U660F rather than the four-cylinder U760F, then compare your old drum's shaft length, splines and ring grooves with the photo. Send us your year, model and VIN if you want us to check. The full parts range for this family is on the U660E and U660F collection page.

Installing the drum

• Flush the cooler and lines; debris from the old clutches will otherwise end up in the new drum and the solenoids.
• Check the case bearing support bore. Gears Magazine documents wear there on this family, and any movement of the outer race means the case needs repair first.
• Fit new input shaft sealing rings, lube them with WS fluid, and air-check C1 and C2 through the case before installing the valve body.
• Check clutch clearance against the factory specification.
• Fill with Toyota WS, set the level at the bulletin temperature using our fluid guide, and perform the ECT memory reset with a capable scan tool.

A burnt drum usually means the valve body has been working hard too. Pair it with a remanufactured U660F valve body or the 2006-2018 shift kit to restore pressure control.

Is this the right drum for an AWD Highlander or RX350?

It fits 2010 and later U660F transmissions, the AWD V6 version. Confirm the transmission tag and compare your old drum with the photo, or send us your VIN to check.

What is the difference between this and the 2007-2009 drum?

Toyota revised the drum during production. This is the late version for 2010 and newer units; early transmissions should use the 2007-2009 listing.

Do I need to buy clutches separately?

Not for this drum. It arrives loaded with new forward and direct clutches, steels and pistons. You will still want gaskets, seals and the other clutch packs from a rebuild kit.

Can a bad drum cause no Drive but Reverse works?

Yes. The forward clutch in this drum is applied in first through fourth, so a failed C1 pack or seal can leave the vehicle with no Drive while Reverse still works.

What fluid does the U660F take?

Toyota WS. Set the level hot through the overflow plug in the Toyota temperature window, then clear the adaptive values with an ECT memory reset.

• Toyota/Aisin U660E and U760E: Shudder, Valve Body Wear, and the WS Fluid-Level Procedure
• U660E Fluid Type, Capacity and Service Interval