U660F Shift Kit 2006-2018

An all-wheel-drive Highlander, Sienna or Venza with the 3.5L V6 six-speed that flares between second and third, loses its grip with throttle in third or fourth, or keeps logging lockup slip codes is usually not a candidate for a whole new transmission yet. More often the valve body has worn in three predictable spots. This is the new TransGo SK U660 shift kit, sold by TransGo as a valve body repair kit for both the U660E and the F-suffix U660F transaxle from 2006 through 2018, and it targets exactly those three wear points.

What the shift kit does in a U660F

The U660F shares its valve body hydraulics with the front-drive U660E, which is why TransGo covers both with one kit. Three valves cause most of the trouble. The TCC boost valve and its bushing wear until the computer can no longer apply and release the converter clutch cleanly. The solenoid modulator valve, which caps the pressure feeding the shift and pressure-control solenoids no matter what line pressure is doing, wears its aluminum bore and lets solenoid feed drift high or low, so line pressure drifts with it. The B2 regulator valve bore wears and leaks, and that leak is what drivers feel as a flare on the 2-3 shift. Toyota's own fluid bulletin lists the U660F as the 4WD version of this transaxle in the V6 Highlander, Sienna and Venza. The kit replaces each with drop-in parts:

• USA-made hardened steel TCC boost valve and bushing
• Hardened B2 regulator outer valve and spring that rides on an unworn section of the bore
• Redesigned solenoid modulator valve, bushing, spring and end plug that restore function in the original worn bore
• A 0.055 in. drill bit for the two separator plate holes the instructions have you enlarge

Symptoms this kit addresses

• Shuttle shift or flare on the 2-3 upshift
• Slipping under throttle in 3rd and/or 4th gear
• Torque converter clutch slip or performance codes, with rpm wandering at cruise
• Shift complaints that track with line pressure reading too high or too low

How to confirm it before you buy

Fluid comes first on these units. Check level hot, at 185-194 F, using the procedure in Toyota's WS fluid level bulletin, because a low level on a sealed Toyota six-speed causes the same flare and slip complaints. Scan every module, not just the transmission, and record freeze frame data. If clutch material is heavy in the pan, the packs are already damaged and the kit alone will not cure the slip. Our U660E and U760E problems and service guide walks through the diagnosis order, and the U660E fluid type and capacity guide covers the fill.

Fitment

This listing is for U660F and U660E transaxles, 2006-2018, per TransGo's application for SK U660E. These are the 3.5L V6 six-speeds. TransGo's instructions state plainly that the kit does not fit the four-cylinder U760E, which takes its own SK U760E. Check the transaxle code on the ID plate before ordering; if you are unsure whether your vehicle has the F or E unit, send us the year and VIN. Every part we carry for this family is on the U660E and U660F parts page, and a front-drive listing of the same kit is the U660E shift kit 2006-2018.

Install notes

• The valve body can be serviced without removing the transaxle, but it is a professional-level job. Mark every check ball and retainer location as it comes out, even where it differs from TransGo's drawing.
• Every retainer must sit below the valve body surface when reinstalled; grind a retainer if it stands proud.
• Do both separator plate steps with the supplied drill. TransGo ties them to keeping the transmission cool.
• If a planetary failed, the valve body must be stripped and cleaned completely before the kit goes in. A damaged gear set is a separate repair, such as the U660F underdrive planetary.
• If the clutches are burned, pair the kit with a U660E master rebuild kit. Refill with Toyota WS and recheck the level hot.

Does this kit fit the U660F in an all-wheel-drive vehicle?

Yes. TransGo lists the SK U660E kit for both the U660E and U660F, 2006-2018. It does not fit the four-cylinder U760E or U760F.

Will a shift kit fix a transmission that already slips badly?

Only if the slip comes from valve body wear. If the fluid is burnt and the pan has heavy clutch material, the clutch packs need replacing; install the kit during that rebuild.

Do I have to remove the transmission to install it?

No. The valve body comes out from under the vehicle, but it must be disassembled on a clean bench and the instructions followed exactly, so it is a job for an experienced technician.

What fluid do I use afterward?

Toyota WS (World Standard) ATF only. Fill and check the level at 185-194 F using the procedure in Toyota's WS fluid level bulletin.

Does it need special tools or reaming?

No reaming. The valves and bushings drop into the existing bores, and the kit includes the 0.055 in. drill bit for the separator plate holes.

• Toyota Aisin U660E/U760E Problems and Service Guide
• U660E Fluid Type and Capacity