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Toyota Sienna Service Manual: When servicing full-time 4wd vehicles

Toyota Sienna Service Manual / Introduction / Repair instruction / Precaution / When servicing full-time 4wd vehicles

The full-time 4WD SIENNA is equipped with the open center differential system.

If incorrect preparations or test procedures are used, the test will not only be unsuccessful, but may be dangerous as well.

Therefore, before beginning any such servicing or test, be sure to check the following items:

CAUTION: • Never accelerate or decelerate the vehicle suddenly • Observe the other cautions given for each individual test

(a) Before Beginning Test

This vehicle does not have a center diff. lock mode or 4WD (Normal) Mode to allow only the front or rear wheel to be rotated.

The test method for this vehicle is different from that for vehicles equipped with the center diff. lock mode or 4WD (Normal) Mode, so make sure to use the correct test method.

Braking Force Test Braking Force Test

(Vehicle Speed: Below 0.5 km/h or 0.3 mph) When performing low-speed type brake tester measurements, observe the following instructions.

(1) Position the wheels to be tested (front or rear) on the tester.

(2) Shift the transaxle shift lever to "N" position.

(3) Idle the engine, operate the brake booster and perform the test.

(c) Speedometer Test or Other Tests

(Using Speedometer Tester or Chassis Dynamometer)

When performing test at high speed or high load, use the methods shown below.

*: This is to avoid damaging the center differential.

NOTICE: • Confirm that the vehicle is securely immobilized. • Never operate the brakes to drive the wheels or stop them suddenly.

(d) On-Vehicle Wheel Balancing

On-Vehicle Wheel Balancing
On-Vehicle Wheel Balancing

When doing on-vehicle wheel balancing on a fulltime 4WD vehicle, to prevent the wheels from rotating at different speeds in different directions from each other (which could damage the center differential), always be sure to observe the following precautions:

(1) All 4 wheels should be jacked up, clearing the ground completely.

(2) The parking brake lever should be fully released.

(3) None of the brakes should be allowed to drag.

(4) The wheels should be driven on the wheel balancer with the engine running.


When doing this, be careful of the other wheels, which will rotate at the same time.

(5) Avoid sudden acceleration, deceleration and braking.

(6) Carry out wheel balancing with the transaxle in D position.

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