U660F Input Drum

When a 3.5L V6 Toyota or Lexus with the six-speed U660F (all-wheel drive) or U660E (front-wheel drive) loses Drive, slips through the gears, or comes apart with a cracked drum or chewed-up piston bore, the part a rebuilder needs is the C1/C2 input drum. This is a used genuine Toyota assembly, OEM part number 35650-33010, with the drum, input shaft and both pistons together. It is priced as a hard-parts core: the shaft splines, gear teeth, drum housing and pistons are sound and reusable, but the steel plates inside show heat discoloration, so plan on new frictions and steels before it goes into your case.

What the input drum does in a U660F

Toyota names it the forward and direct clutch drum. It is splined to the input shaft, so it spins with the converter turbine at all times, and it holds two clutch packs. C1, the forward clutch, connects the input to the gear train in first through fourth. C2, the direct clutch, is applied in fourth through sixth. Fluid reaches each piston through sealing rings on the shaft, which means a slip can start at the frictions, at a piston seal, or at worn ring lands that bleed off apply oil. The U660F shares this layout with the front-drive U660E; the all-wheel-drive hardware sits after the gear train, which is why the same 35650-33010 assembly serves both.

Symptoms that lead back to this drum

• Engine flare on takeoff or on the 1-2 and 2-3 upshifts (C1)
• Slip on the 4-5 shift or in sixth at highway speed (C2)
• No movement in Drive while Reverse still works
• Burnt fluid with friction lining and metal on the pan magnets
• Gear ratio or slip codes that come back after towing or a hard pull

How to confirm it before you buy

Start outside the transmission. Gears Magazine notes that a carbon-coated throttle body or a lazy MAF sensor can produce harsh downshifts on this family that feel like an internal fault, and that the wrong fluid alone can cause flared shifts and solenoid codes. Scan every module, then check the fluid is Toyota WS and set at the correct hot level. A light-throttle shudder between roughly 25 and 50 mph is flex lockup, not this drum; driving in Manual 3 separates the two. If the slip is real, read C1 and C2 apply pressure. Good pressure with slip condemns the drum and its packs, while low pressure points to the pump or valve body. Our U660E and U760E problems and service guide walks through that sequence.

Fitment

This drum is for the V6 U660E and U660F. The listing names the 3.5L V6 Camry (2007-2017), Avalon (2008-2018), Lexus ES 350 (2007-2018), Highlander (2008-2016), Sienna (2011-2016), Venza (2009-2016) and Lexus RX 350 (2010-2015). The four-cylinder U760E and U760F use a smaller drum with fewer plates that will not interchange. Toyota also revised this drum during production, so read your transmission tag, match the 35650-33010 number or compare shaft length and lug pattern with the photos, and if anything looks different, send us your year, model and VIN before ordering. Late-design and early-design alternatives are listed with every other part for this family on the U660E and U660F collection page, including the 2010-up U660F input drum.

Install notes

• Strip the drum, discard the heat-marked steels and old frictions, and build both packs with new plates; the U660F master rebuild kit covers the frictions plus every seal and gasket in the unit.
• Fit new piston seals if they have taken a set; the U660E bonded piston set is the clean option if a piston lip is torn.
• Check the shaft bushings and ring lands, install new sealing rings lubricated with WS fluid, set C1 and C2 clearance to spec, and air-check both pistons.
• Inspect the case bearing bore; Gears Magazine reports wear there on U660E cases, which lets the drum run off center.
• Flush the cooler and lines, refill with Toyota WS, set the level hot per our U660E fluid type and capacity guide, then reset adaptive values and road-test.

Can I install this drum exactly as it comes?

Not recommended. The drum, shaft, gear teeth and pistons are in sound, reusable condition, but the steel plates show heat discoloration. Treat it as a rebuild core: fit new frictions and steels, set clearance and air-check it before installation.

Does it fit both the U660E and U660F?

Yes. Part number 35650-33010 is listed for the front-drive U660E and the all-wheel-drive U660F, the V6 six-speed used behind the 3.5L engine in the Camry, Avalon, ES 350, Highlander, Sienna, Venza and RX 350.

Will it fit a four-cylinder Camry or RAV4?

No. Four-cylinder models use the U760E or U760F, which has its own smaller forward/direct drum with fewer clutch plates. Check that your transmission tag reads U660E or U660F.

What else should I replace along with it?

New frictions and steels for C1 and C2, input shaft sealing rings, and any hardened piston seal. If the old drum failed and shed lining, a full master rebuild kit and a cooler flush are the safe choice.

What fluid does it need, and is there a relearn?

Toyota WS ATF only, with the level set at operating temperature through the overflow plug using Toyota's WS level procedure. Clear the transmission adaptive values with a scan tool and road-test so shift timing relearns.

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