Just rotated my tires on my SE phev, but now l have a puzzle. I jacked up the car on 4 jack stands and proceeded to rotate the tires. The car was in park (the transmission gear selector was in P) and l had the parking brake engaged. Since the wheels were off the ground, l noticed that the fronts would rotate when l tried to tighten the lug nuts at higher torques. But the rears would not rotate at all because of the parking brake. This puzzled me, so after l lowered the car and drove it once around the block, l put it in P without the parking brake engaged and turned the car off. Then l tried to push the car by hand, but after rolling forward maybe 1 cm, l could feel the parking pawl stop the car. But then l could not figure out why the parking pawl did not lock the front wheels when the car was lifted. Any idea why? Something to do with the front differential perhaps?
I had the same experience with a 2005 Prius the other day... It was concerning because there was a light slope where I had to do the jacking... Made me nervous and no idea why parking wouldn't work to hold wheel when its up in the air.
Did they turn the same direction, or in opposite directions? The parking pawl should be on the engine side of the front differential. When the car is rolling on the ground with normal traction on both front wheels, they normally can spin only in the same direction, so there is no need to block the opposite direction spin component. But do remember that when one front wheel is off the ground, the other front wheel won't contribute to keeping the car stationary.
Just noticed it on a 2007 on jack stands too and figure it out. The parking system locks up the car ability to move forward or backwards with both wheels. However it doesn't lock the differential so if you spin one wheel forward the other wheel will spin backwards. As long as both wheels move in same direction the parking system has got you covered.
When l got one front wheel on my gen5 to turn when tightening the lug nuts, l did not think to have someone check the other front wheel to see it it was turning the opposite way. But in hindsight, with the front drive system having a differential, now this all makes perfect sense. I think?
I appreciate you posting this because it was same thing I noticed but didn't think to look at what other wheel was doing as well... So thanks for encouraging me as well others to better understand what can happen on jack stands.
In each case, the front wheels would each spin clockwise when l was tightening the lug nuts firmly. Also, what do mean that the parking pawl is on the "engine side" of the front differential? What side is the "engine side"?
Regarding torquing the lug nuts, a couple of thoughts: 1. When raising the car, try to end up the with the wheels just a slight amount clear; a finger width is ideal, an inch at most. This makes for less lift when reinstalling the wheels (which can be a handful), AND it makes it possible to effectively jam a wheel chock twixt tire and slab, hold it with your foot, to prevent wheel rotating while you snug the lug nuts. 2. Lowering the car with the lug nuts firmly snugged is ok. Do the final torque to spec with the car on the back on the slab. This is easier, and safer. FWIW, my drill for for raising the car: 1. Jam heavy-duty, rubber wheel chocks fore and aft of each rear wheel, then release parking brake. (this pins the rear wheel, while allowing the car to "hinge" on the rear wheels. 2. Raise front and settle onto jack stands. 3. Raise rear and settle onto jack stands. (lower in reverse of above)
"Clockwise" is simply because of the right-hand threads. "Righty-tighty, lefty-loosy." But that isn't what I meant for direction. Instead, when the input shaft of the differential is locked, if you turn one wheel in the forward direction, the other wheel should turn in the reverse direction. If you looked through under the car to the opposite wheel, you should have been able to see the other wheel turning, and see whether it was turning in the forward or reverse direction. It looked like you had it figured out at post #5. Like Mendel, I only moderately tighten the lug nuts while the wheel is in the air, then do the final torquing after it is on the ground. The differential has 3 shafts. Generically, the engine and transmission (for a Prius, this includes ICE / MG1 / MG2 / parking pawl assembly) are all out on one shaft. Each other shaft carries a single drive wheel. On a differential, if any single shaft is locked, the other two should still be able to turn, but their motions are tied together. If the engine-power shaft is locked, and one wheel is turned, the other wheel must turn the opposite direction at exactly the same rate.
Yes, in hindsight, l should have just looked at the other front wheel when l turned the nearest front wheel. And, yes, good advice about tightening. I torque each bolt to around 50 foot-pounds when in the air and then torque to the spec of 76 foot-pounds once the car is down.
