Jacking up the rear of the Car (Floor Jack)

[Rv-Junke]

Other than the Rear Diff not sure you can get the whole car up in one shot...I know you are not "supposed" to do the Diff, but I have been told by numerous service tech's that that is because the car is unstable when lifted by just the center point in the rear and if you don't pad or use something to stable the diff it slides off of jack stands. Using it carefully and then adding jack stands once in the air or the race ramp product blocks (I personally love these) you "should" be ok, but it is a risk. Option is jack one side up at a time (I personally don't like that method seems more unstable), so I am a Diff guy who takes extra precautions...this is of course my opinion. Now I am considering this for the 2015 since it is more for a IRS opposed to the live axle on my 2014.

Amazon:

http://www.amazon.com/Steel-Floor-J...sr=1-2-catcorr&keywords=floor+jack+cross+beam

Used to do Cat Back

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[89Trooper]

because the car is unstable when lifted by just the center point in the rear and if you don't pad or use something to stable the diff it slides off of jack stands.

This is the reason right here... because it can be unstable, and could be unsafe. That's why they would never recommend it.

It's funny, I did a search for "differential jacking" and found many forums with this same argument.

It's ok.
Don't do it.
You can do it.
I would never do it.
Do it.
No way!
I always do it.

:lol:

 

[Rv-Junke]

Hey Trooper...long time no talk. Happy New Years...also, your car is looking awesome BTW!

Yeah, this is a preference issue with no right answer and plenty wrong answers. I like the cross beam add to the floor jack, but it wouldn't work with solid axle, so I used the diff and hold my breathe...I'm 99% sure ill buy the above add to my floor jack...looks a hell of a lot safer. LOL!

 

[89Trooper]

Hey Trooper...long time no talk. Happy New Years...also, your car is looking awesome BTW!

Yeah, this is a preference issue with no right answer and plenty wrong answers. I like the cross beam add to the floor jack, but it wouldn't work with solid axle, so I used the diff and hold my breathe...I'm 99% sure ill buy the above add to my floor jack...looks a hell of a lot safer. LOL!

Happy New Year to you, too! And, thanks!

That is a great idea! I didn't even know something like that existed.

 

[Rv-Junke]

Why these forums are good... :-)

 

[WestRace]

"Claimed" ???

That's where cars have been jacked up since there were cars to jack up!

Are you an "engineer"? Or an "engineering student"?

At 5 years old my parents caught me jacking up my mothers 396 nova SS by the diff. It isnt a new theory, it isn't rocket science, it isn't claimed, it's where rwd cars and trucks get jacked up

I can't speak for others, but here is a pic of the diff. It is mounted to the subframe by four screws so when the car is jacked up at the diff, at that moment the four screws are the only things that are used to support most of the weight of the car, which to me too risky. In normal operation, the subframe mount points and the suspensions are meant to support the car, the diff only has to withstand the lateral force from the torque of the turning drive shaft.

The pic below shows that each side, there are two main side rails that serve as the main support for the car structure. You can jack up at one point of the rail then put the jack stand on the other. As long as the jack point at the main rail, I think it should be OK.

There are a couple of vid where they show how the car is jacked up.

[ame]

[ame]

 

[mc lane]

well
one Thing is for sure
a 396 Nova ss is no rocket science and has a solid axle like a truck
the s550 has no truck axle any more

 

[69mach1-395]

Recommended, or not, this is true.

Just stay away from the cover, and you'll be fine.

Irregardless (I love using that word) of what Ford Service says, I will continue to do it.

I don't think that is a word, irrespective of how many times people use it.addle:
http://www.urbandictionary.com/define.php?term=irregardless:cheers:

 

[mc lane]

I can't speak for others, but here is a pic of the diff. It is mounted to the subframe by four screws so when the car is jacked up at the diff, at that moment the four screws are the only things that are used to support most of the weight of the car, which to me too risky. In normal operation, the subframe mount points and the suspensions are meant to support the car, the diff only has to withstand the lateral force from the torque of the turning drive shaft.

The pic below shows that each side, there are two main side rails that serve as the main support for the car structure. You can jack up at one point of the rail then put the jack stand on the other. As long as the jack point at the main rail, I think it should be OK.

There are a couple of vid where they show how the car is jacked up.

if you take a second look, it does not only appear risky because those 4 screws have to carry the load. there are many Tasks for the subframe, but the Task of carrying the load is NOT one of them. the weight of the car is carried by those 2 coil-springs located between the lower arms and the carbody.
that is why you could do the jacking up under the diff (given the solid axle was robust enough) because the weight was transferred from the solid axle to the leafsprings or coils carrying the weight (being connected to the carbody)

 

[89Trooper]

I don't think that is a word, irrespective of how many times people use it.addle:
http://www.urbandictionary.com/define.php?term=irregardless:cheers:

I love it because of this:

[ame]

 

[WestRace]

if you take a second look, it does not only appear risky because those 4 screws have to carry the load. there are many Tasks for the subframe, but the Task of carrying the load is NOT one of them. the weight of the car is carried by those 2 coil-springs located between the lower arms and the carbody.
that is why you could do the jacking up under the diff (given the solid axle was robust enough) because the weight was transferred from the solid axle to the leafsprings or coils carrying the weight (being connected to the carbody)

It's true that the springs and shocks have to shoulder large percentage of the weight, but the subframe has to support part of the weight because the suspension control arms pull on the subframe which is part of the body. So the force of the control arms act on the subframe which in turn acts on the body. I guess you have to do a vector analysis on those points to figure out the actual percentage of the force of each points : suspension, shocks, and the four subframe mount points.

If you feel the four screws that hold the diff to the subframe is enough to support the weight, well it's your car ...

As for the live-axle, I am not too familiar with it so I can't comment.

 

[IGJoe2192]

Do not use the diff. If you are on any sort of incline or decline, the car will roll as you take its only form of holding itself in place (the rear wheels)

USE THE DESIGNATED LIFT POINTS ON THE LEFT AND RIGHT SIDES OF THE CAR. They should be located along the rocker panel just after the front tires and before the rear tires.

Also, ignore all of this noise about how it can be done. Anyone who argues for lifting the car from the differential is just a backyard mechanic.

 

[Husker]

 

[USPSALIMITED]

Do not use the diff. If you are on any sort of incline or decline, the car will roll as you take its only form of holding itself in place (the rear wheels)

USE THE DESIGNATED LIFT POINTS ON THE LEFT AND RIGHT SIDES OF THE CAR. They should be located along the rocker panel just after the front tires and before the rear tires.

Also, ignore all of this noise about how it can be done. Anyone who argues for lifting the car from the differential is just a backyard mechanic.

From the original post.

"BTW, this is not to hold the car up while working on it, Jack stands would be inserted when it is at an appropriate height. Front wheels will also be chocked."

Need to lift at one point and slide in supports at another.

What is wrong with being a back yard mechanic?

 

[mc lane]

It's true that the springs and shocks have to shoulder large percentage of the weight, but the subframe has to support part of the weight because the suspension control arms pull on the subframe which is part of the body. So the force of the control arms act on the subframe which in turn acts on the body. I guess you have to do a vector analysis on those points to figure out the actual percentage of the force of each points : suspension, shocks, and the four subframe mount points.

If you feel the four screws that hold the diff to the subframe is enough to support the weight, well it's your car ...

As for the live-axle, I am not too familiar with it so I can't comment.

PULL is the word
if you do a vector Analysis just for the vertical Forces, one can see soon, that as Long as the car is Standing on its own wheels (that is what it is designed for) there is Tension, not pressure, on the subframe...
if in modern, Computer aided designs, focussed on weight saving, the components carrying that subframe, are able to take that amount of pressure (when a jack is put under the diff)?
only :ford: knows...
but why should they do it? they probably do not design the boot-floor or other parts of the car do cope with such loads

:cheers: we should ask :ford: or find someone brave enough to test the s550 diff

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