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How to jack up car from the rear.

I know this topic has been beaten so many times but I have never heard anyone talked about jacking up the rear at the control arms, the lowest point right where the wheel is. I did this several times and feel more safe than jacking it up at other place I can see.
Anyone see that I shouldn't be jacking it up at this control arms?
Thanks
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Old 08-08-2008, 10:06 AM
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I would not recommend jacking up a car on a suspension piece. These pieces by their nature shift and move. Not the sort of thing you want to take chances with IMHO.

BTW, what's wrong with the points porsche reccomends using?
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Old 08-08-2008, 10:14 AM
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If your lifting both wheels at the same time just jack it up on the engine case.
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Old 08-08-2008, 10:19 AM
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I think that's exactly the source of all the controversy. Some people say never ever jack the crankcase, some say don't be silly, it's perfectly safe.

I'm with the never ever crowd...
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Old 08-08-2008, 10:22 AM
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I want to leave the jack points for jack stands, and don't feel safe jacking up at the case. I affraid it's "too thin". I know many of you will slame me but let just say it's just me, even if I am wrong on this. I tried it once or twice but the whole time jacking it up, I always affraid if the 20+ year old aluminum case crack on me, I'll be sitting here and cry alone. I just can't be happy/enjoy babying my car with that feeling in mind.

Can someone please point out what can happen if I have a long strong metal pipe accross from left to right at the bottom of that big control arms? Or any other lift points to lift both side at once on the rear?
Thanks.
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Old 08-08-2008, 11:49 AM
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I usually jack the car up with the jack near the engine/transmission interface. Sometimes at other spots on the case. I've never heard of any damage to an engine or a case from jacking it up. But some people prefer to be super-safe.

-Wayne
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Old 08-08-2008, 11:55 AM
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If it helps, the case is not a shell. It is a very structural piece with about 1" thick webs running through it at every crank journal.

It is capable of handling the force of up to 1000 hp trying to tare it apart under some turbo applications.

If you use a pad on you jack you should not have any issues.

Just a thought.
Old 08-08-2008, 01:24 PM
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OK, I'll beat this horse one more time - the factory manual says "NEVER" jack up the car using the engine and Roland Kunz implies that you're an idiot if you do this.

I'm curious why people do this, is it to save time? How much time do you save? People always claim that it does no damage...... does your engine leak? Hmmmmm.

Would you jack up your other car or your wife's car under the engine?

I don't get it.
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Old 08-08-2008, 01:46 PM
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Quote:
Originally Posted by rnln View Post
I want to leave the jack points for jack stands...

Can someone please point out what can happen if I have a long strong metal pipe accross from left to right at the bottom of that big control arms? Or any other lift points to lift both side at once on the rear?
Thanks.
There's really no need to go where "no man has gone before" on these cars . I jack mine the way Porsche intended, using a jack pad inserted into the rocker jack points, one side at at time (while being careful with the geometry). When you say jack points, I'm assuming you're referring to the Carrera "jack pads" (indeed, they would be the jack points if using a lift). If you want to use them, let your torsion bar covers "cradle" in the jack stands for support. That's where I place my jack stands anyways on the rear unless I'm doing suspension work, as I feel that's even more secure than using the Carrera jack pads.
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Old 08-08-2008, 02:02 PM
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911st,
How about bolts/nuts and seal which to keep them from breaking, leaking. I might be too careful or too scared but I just don't feel comfortable. So I am trying to find a solution that makes me feel more comfortable Actually I am hoping there are places (side by side) so that I can lift it once, for both sides.

KC911,
When I said jack points, I meant the 4 points underneath the bottom for lifting purpose. Sorry I wasn't clear. I can't use the factory jack at the factory holes anymore since it's converted to slantnose with the side bar which don't have jack holes.
On the torsion bar covers, do you think those 4 bolts are strong enough to be 100% safe laying under the car? I am not sure about this, they might be safe but I why can it be safer than jack pads?
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Last edited by rnln; 08-08-2008 at 02:22 PM..
Old 08-08-2008, 02:17 PM
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Quote:
Originally Posted by Wayne at Pelican Parts View Post
I usually jack the car up with the jack near the engine/transmission interface. Sometimes at other spots on the case. I've never heard of any damage to an engine or a case from jacking it up. But some people prefer to be super-safe.

-Wayne
I agree. I do it on the case.

--John
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Old 08-08-2008, 02:19 PM
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Quote:
Originally Posted by rnln View Post
KC911,
...On the torsion bar covers, do you think those 4 bolts are strong enough to be 100% safe laying under the car? I am not sure about this, they might be safe but I why can it be safer than jack pads?
Absolutely secure! Remember, it's not just the 4 bolts, you've got your torsion bar in there too, and that's what folks used prior to the appearance of the Carrera jack pads. In my opinion, the torsion bar covers cradled in my jack stand's top \__/ are even more stable than the pads sitting flat on a piece of 2x4 on top of a stand. That's what I've always used after trying/evaluating both ways.
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Old 08-08-2008, 02:28 PM
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I understand your fear. I have felt the same way.

I learned this from two independent Porsche shops that have done if thousands of times. I use a pice of 2x6 with the grain perpendicular to the case halves and make sure I am not resting on something else.

Thinking out loud, the further you are with your jack point from the front wheels, the less the load at the jack point.

I am guessing but there may be less stress on components jacking near the center of the motor than at the intersection of the trans and motor. Not that it would make it less viable. Just an uneducated guess.

There really are not very many good places to jack a 911. I actually feel more at risk using the side jack points. I fear them sliding out as the angle increasses. I had evidence of such an issue on a 914 and one of the 911's I had owned.

Also bought a 72 911S that had the one year only hard to find oil cooling lines crushed by someone putting a jack under the side.

I be taking me chances.

Finding a way to center jack the front is fun to.
Old 08-08-2008, 02:48 PM
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The reason I always jack from the case is I maintain a safety triangle that way. Both front tires remain on the ground, so I know it can't shift sideways. Also, I am usually doing something on both sides of the car (brake pads, height adjust, etc.) so it saves time. I watch some fellow racers jack their cars from one side, then the other, and it always looks like it's a precarious operation. One small bump and the thing will crash down on the jackstand, shoving it through the body.

220k on my DD, jacking the motor always, and no issues. I can't see why it's done any other way.
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Old 08-08-2008, 02:54 PM
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Quote:
Originally Posted by Wayne at Pelican Parts View Post
I usually jack the car up with the jack near the engine/transmission interface. Sometimes at other spots on the case. I've never heard of any damage to an engine or a case from jacking it up. But some people prefer to be super-safe.

-Wayne
The engineer in me screams that this has to be the worst place to jack it up.

a) it is the midpoint of a long span between two fixed pivot points. if it was a solid beam, this would be the point of greatest deflection. no, it's not going to bend, it's going to...

b) the source of integrity for this interface are studs embedded into either aluminum or magnesium. possibility of pulling a stud would be higher by jacking here than, say, under the sump plate.

I don't own one, but this jack pad places the jacking force near the fixed pivot points (rear engine mounts). However, this relies on the structural integrity of the rear clip to lift up the car (probably close to 1500lbs on a 2500lb car).

Somewhere between the sump and the pulley would be my personal choice.

PEL-PP915232

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Old 08-08-2008, 03:20 PM
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OK, I'll beat this horse one more time - the factory manual says "NEVER" jack up the car using the engine and Roland Kunz implies that you're an idiot if you do this.
There are also factory tech bulletins that say NEVER lower the car, and NEVER install aftermarket chips in a DME car, NEVER change redline ont the engine, as well as NEVER install different type tires front / rear (I subscribe to that one), and probably NEVER alter the factory alignment settings and tire pressures ...

I use the case. My engine leaks. At the chain housing to head interface. Probably not due to jacking on the case if I had to guess.
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Old 08-08-2008, 04:30 PM
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Here's a picture of Tom Amon. He does all of his work in the field(you house)
http://www.mobileworkswest.com/customers_1987Overhaul.html

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Old 08-08-2008, 05:09 PM
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Jack

I place towels on the jack "cradle" to protect the case, then let it "cup" the area around the oil drain. Been doing it this way a long time, never a problem.
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Old 08-08-2008, 05:30 PM
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Thanks guys.
Looking at the pic below, I can't see where is his jack point of the front. Can anyone see it?

Quote:
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Here's a picture of Tom Amon. He does all of his work in the field(you house)
http://www.mobileworkswest.com/customers_1987Overhaul.html

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Old 08-10-2008, 09:50 PM
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Looks like the jack point by the A-pillar. The car sits quite happily on 3 points - even attempts at jacking the front up evenly with 2 jacks result in lifting the car on one side or the other when the rear of the car is on jackstands.

I'd put a jackstand on the other side as well, though ...
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Old 08-11-2008, 01:56 AM
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