I do this 3-4 times/year when rotating tires or swapping winters for summers (or vice versa) and I got the location of the center floor jack lift points from a shop service manual.
First, some safety..
- Always inspect and check the operation of your equipment prior to each use.
- Always use two jack stands -- no more, no less -- and always chock the wheels opposite the end being jacked up.
- Always center the floor jack under the vehicle. If placed off to the side the car could shift unexpectedly, potentially crushing anything/anyone underneath it.
- Never climb under a car supported by the jack alone. If it failed (and they can and do) while you were under there, you would be crushed to death.
- Never jack up a car on an uneven surface. It could shift unexpectedly, potentially crushing anything/anyone underneath it.
- Jacking a car up can be dangerous. Proceed with caution and at your own risk. I shall not be held responsible for any damages or injuries related to an omission of fact.
You'll want a low-profile floor jack (~5" height; taller ones won't fit under the front end, especially if you have a lowered suspension), a couple of 2-ton (or greater capacity) jack stands, a pair of wheel chocks and a few pieces of 3/4"-1" thick plywood -- two (2) about 12"x12" to drive the car onto and one (1) about 5"x5" to put on top of the jack's liftplate so as to protect the car's underbody from metal-on-metal damage.
Make sure you have plenty of space in front of and in back of your 3 to maneuver the jack into place. If jacking up the front, drive your 3's front wheels up onto the two larger plywood pieces -- this will give the jack the clearance needed to get under the front end without deforming or damaging the air dam or the plastic undershield (at least not significantly). Then place wheel chocks behind the rear wheels to jack up the front of the car, or in front of the front wheels to jack up the rear of the car.
For the front end, you want to place the jack's lift plate underneath the front suspension's crossbrace just rearward of the axle plane. If you look, just behind this point there's another crossbrace that seems less "beefy" -- DO NOT jack the car up by this brace; use the aforementioned larger brace area just forward of this one.
For the rear, you shouldn't need to use the larger plywood pieces under the tires as there's likely enough clearance without them, but I'm in the habit of using them anyway, if only because they allow some lateral movement of the tires when letting the car back down. The rear crossbrace jack point should be quite obvious -- it's right between the lower suspension beams and has a "bump-out" in the middle about the same size as most jack lift plates and kinda shaped like (ignore the .'s):
(Rear)
. / \ .
.| . |.
. \ / .
(Front)
...if you looked at it from directly beneath it. Center the jack's lift plate on this bump-out.
After jacking up one end of the car, place the jack stands under the corner jack points one would use for the emergency jack. (Note: You'll likely find that the yoke of the jack stand isn't nearly deep enough to accommodate the sheet metal rib between the two markings indicating the jack point. I have no ready solution for this other than to place the yoke parallel with the rib on the inside edge of it rather than perpendicular to it; there seems to be just enough metal there. So far, this is the only safety compromise I make while performing jacking procedures and I most certainly don't recommend following my example. I'm working on fabricating a pair of wooden jig blocks to fit on top of the yokes that will interface with the sheet metal rib in a more correct and perpendicular fashion.) Check their positions and then slooooowly lower the car onto the stands, being ready to re-lift if a stand shifts or otherwise fails.
For safety, leave the jack lift plate in contact with the central jack point and apply a slight amount of lift to it, but not enough to lift it back up off of the stands. Then raise the jack handle until it contacts the underside of the bumper. There are three reasons to do this, although the first two aren't necessarily entirely logical.
One is so that, if a jack stand does fail or slips or is knocked out of position and the car begins to drop, any downward movement of the car will cause the jack to attempt to lift it more. Likewise, if the jack begins to fail resulting in downward motion of the car, its motion should be at least minimally retarded by the pressing down of the jack handle. Lastly, and most importantly, the jack handle being up in the air is easier to see and avoid and almost impossible to trip over.
I hope this information is helpful. Any corrections are greatly appreciated.
Maybe someday I'll take pictures and post a full How-To in the How-To section...
