Jacking your BMW

[632 Regal]

Who jacks their BMWs on the differential and front cross tube?

[scott540]

Not me, Yet :D

[DaveR 91 535ia, 71 02]

I do

[zmuff]

Okay, I'll admit it, I have jacked my car by the crossmember and differential a few times. I was very careful and used sacrificial wood blocks as suggested on Gale's Repair Page (I'm probably going to get flamed for this too!). I knew of the controversy mentioned on several websites prior to jacking it that way, but tried it out anyway with no apparent ill effects...this time. But when the dust settles from this poll, if the facts outweigh the opinions, I am open to changing my ways.

[Tiger]

No way...

[Paul in NZ]

:d

[ryan roopnarine]

should be "jackin" their bmw....perhaps you have too much of an emotional investment in your car ????? :D :D :D :

[winfred]

i do

[ryan roopnarine]

tuborgs and a na$ty milwaukee's best can't possibly be wrong.

[632 Regal]

Winfred does?

[Cacatfish]

I did on older cars like e28 and such, but this one just feels heavier and maybe a little more valuable, so I stick to the factory points. I would never do the diff, but the front and rear cross-members probably wouldnt hurt the car.
BTW: never trust your jack only. Use stands or at least blocks....

[dave b]

I do the factory points only!

[scott540]

This is some good stuff. thanks for starting the poll Jeff

[632 Regal]

I guess people do lift them on the crossmembers, I dont think I will but at least we are learning stuff here. Thanks to Glen I think my foot will be stuck in my mouth on this one.

:(

[DueyT]

Well Jeff, I figure I'd give you something to keep the interest factor up over lunch! ;)

I used to use the factory points, but I wasn't getting a warm fuzzy about twisting the frame to lift a lowered car up onto those points.

I lift the front up with a wide block of wood under the cross member. IMHEO, linear lifting forces distributed over the structural member that forms the central load transmission path from front wheels to frame is not inconsistent with what that structure does 24/7, 365 days a year.

Now...the rear diff? I haven't done that yet and I'm not too sure it's a good idea. If I do a rudimentary stress-strain analysis of structural load transmission path from rear wheels to frame, the differential casing does not form a part of that load path. The rear struts and trailing links are what transfers vehicle weight to the wheels and Newton #2 says action-reaction, vice versa when lifting up. If the point is to get a single lift point to lift the entire rear (after already lifting the front and using jack stands under the fron factory lift points), I would say that you should either use some device to bridge between the two rear lift points or gingerly lift each side a bit at a time. The second option may not be any better for the frame since there might still be some twisting force if the fronts are already placed on jack stands...maybe ramps are better to allow for some twist. Is there a snubber on the diff that would contact and pass lifting forces to the frame immediately above the diff casing?

Overall, the front cross member is a point intersecting the standard load path...that's fair game as far as I'm concerned. The diff is not, however, and lifting by the diff casing I think is something that you do as a calculated risk. If there isn't a snubber assembly on the casing, I'd hate to think of the tangential forces acting on the drive shafts, trailing links, etc... by lifting an otherwise "floating" differential. As food for thought, consider that a vertical force applied to one end of a fixed-length beam (half-shaft) that casues a 5 degree deflection results in a lateral pulling force 11.4 times the original vertical force ( force(lat) = force(vert) * 1 / tan (horiz. deflection angle of beam)). This could equate to 5 tons lateral force per half-shaft on a 3800lb car with 50% weight on rear wheels. Even a 15 degree deflection angle still results in 3.7 times the applied vertical force...

Hmmmm....

What do you figure, Jeff? Front OK! Back...maybe a rethink?

Cheers,
Duey

[MikeV]

The diff isn't really floating, if I recall correctly (not that that's a given) there are rubber bushings/mounts on the rear of the diff carrier, and it is straight-bolted to the rear subframe crossmember. So the 'float' of the diff is entirely the give of the rear diff carrier bushings and the subframe bushings. I would think the live loads they are subjected to are much worse than the static load from jacking (but that is just a guess).

Now, the diff case, that's another story... but it is pretty massive.

[632 Regal]

I lift the front up with a wide block of wood under the cross member. IMHEO, linear lifting forces distributed over the structural member that forms the central load transmission path from front wheels to frame is not inconsistent with what that structure does 24/7, 365 days a year.


Duey, Doesn't the load from the front go to the top of the strut tower and get distributed into the unibody/frame? The crossmember ties the thrust arms and frame/unibody together, how do you feel that it holds all the weight in the middle of the crossmember? I know chrome moly is strong but I still dont think it was designed to withstand such vertical lift.

[DueyT]

Jeff, you're right about the loads...the cross member actually takes primarily vertical loads as transferred down from the strut towers and redirects them into lateral loads as augmented/balanced by the lower control arms. I guess I'm happy enough that with the big arse piece of wood I use under the cross-member, I'm (almost) effectively lifting concurrently at the outer portions and, for the most part, vertically up to the strut towers.

Duey

[George M]

I personally wouldn't lift on either the engine X-mbr or the diff. I use a hydraullic jack and lift each side incrementally on the jacking points, then place a jack stand under the front frame rail box section on each side and a jack stand under each rear suspension trailing arm. This one can be kicked to death because there are a lot of ways to lift these cars and no immaculate solution. The engine crossmember is a two piece clamshell deep draw stamping welded together and designed to sustain the weight of the engine and lower control arm attachment and not to sustain the entire weight of the car even if you use a generous block of wood to distribute the load. That said, people have been jacking on the engine X-mbr for years...I never have. Duey makes a good point about corner jacking and attendant stresses but overall frame torsional strength is designed to locally jack the car on each corner and hence stresses imparted are lower than the amount of stress relative to strength of loading the engine crossmember by jacking the entire car weight...approx. 2000 lbs of force versus approx 1000 lbs force at the vehicle corner attenuated over the vehicle frame designed to handle the localized point loading due to jacking. As to jacking on the diff...again something I would never do...not only taxing the compression strength of the differential case casting but the localized loading of the diff into where it is connected to the unit body of the car. Jack the car on its jacking point and place a jack stand under each trailing arm that is designed to bear 1/4 of the overall vehicle weight of the rear of the car. Vertical jacking on the diff will not impart resultant stresses to driveline or rear suspension components.

That said, people will continue to jack up their cars how they want :-).
George

[DueyT]

I heard about this years ago, but never really followed up on it...does anyone make a light-duty commercial/home lift? IIRC, the system was relatively simple to install on a flat slab of concrete, and could be relatively easily removed and moved as well?

Anyone welded up their own?

Cheers,
Duey

[DueyT]

Looking at the amazingly symmetrical poll results, at least it's good to see that none of us are losing our marbles!:p

Duey

[632 Regal]

A friend of mine went to an aution a few months ago and called me asking if I wanted one, I said how much he said he didnt know but didnt have any money anyway. So he calls me a couple hours later to tell me that there was 13 total, only 3 sold and the highest one sold for $750.00US. These were from a huge service center for a company, cost over 15k new. He found the auction on the paper. The rest of them were sold to a scrapper for 500 bux.

[DueyT]

I heard about this years ago, but never really followed up on it...does anyone make a light-duty commercial/home lift? IIRC, the system was relatively simple to set up on a flat surface, and could be relatively easily moved as well?

Anyone welded up their own?

Cheers,
DueyNevermind...I found it....the Kwiklift ramp system (http://www.kwiklift.com/).

Cheers,
Duey

[Bill R.]

It very portable and fairly reasonably priced.. I saw a review in a older issue but can't find it now.. Here's the link to their page (http://www.gesforless.com/product_info.isg?products_id=165)







Nevermind...I found it....the Kwiklift ramp system (http://www.kwiklift.com/).

Cheers,
Duey

[Jon K]

I think a fair cross-poll would be "Who here has driveshaft shimmy?" :p

[DueyT]

It very portable and fairly reasonably priced.. I saw a review in a older issue but can't find it now.. Here's the link to their page (http://www.gesforless.com/product_info.isg?products_id=165)
Bill, how much does that kit weigh altogether?

Duey

[Airborne01]

...then place a jack stand under the front frame rail box section on each side ...

I know this is an old beaten-to-death subject, but does anyone have a pic of the "Frame rail box section" I am pretty sure I know what part they are talking about, but with me under the car pretty sure just ain't going to fly.

[Ross]

Crossmember and diff for me. Been doing it for decades with no problem.
What I'm curious to know about is where people choose to put the jack stands.
In front I typically use the subframe rails, in back I usually go for the plate over the big bushing if I need the suspension to hang.

[E34-520iSE]

Yep, I hoist it up by the diff and crossmember too, no mucking about - roll the jack under, lift up, job done. I do use a piece of sturdy timber under the front crossmember tho, just to protect the underseal. I put the axle stands on the chassis rails too, and if I'm just jacking one rear wheel up I simply jack straight onto the metal plate as Ross suggests. I have Bruno's bush inserts installed and this direct jacking hasn't done them any harm at all. This thread is still relevant so it's nice to see it 'bumped'

HTH,

Shaun M

[tim eh?]

Who jacks their BMWs on the differential and front cross tube?

errr i try not to jack at all. be gentle.

[MBXB]

http://www.ezcarlift.com/

[bubba966]

I use the jack points to lift my M-Sport up as the damn thing sits too low to try much anywhere else.

Don't have jackstands yet. But I do have 4 ramps I use to rest the car on. It'd be real nice if I could actually drive the damn thing up onto a set of ramps, but that isn't possible. Couldn't even do it on a set of Rhino Ramps which are a good bit shorter than my NAPA ramps.

[whiskychaser]

Trolley jack under the jacking points. Axle stands under the chassis rail at the front or sills at the back. Yeah, mine will stand it. Not commenting on practise of putting jacks under diffs or subframes. Not climbing under one raised like that either:D

[winfred]

use a couple foot piece of wood to get up the ramp without clearing off the spoiler, makes the ramp less of a sharp approach


I use the jack points to lift my M-Sport up as the damn thing sits too low to try much anywhere else.

Don't have jackstands yet. But I do have 4 ramps I use to rest the car on. It'd be real nice if I could actually drive the damn thing up onto a set of ramps, but that isn't possible. Couldn't even do it on a set of Rhino Ramps which are a good bit shorter than my NAPA ramps.

[632 Regal]

I was wondering when I did a poll that didnt work... figured I must have been too drunk to remember until I realized how ancient this was...LMAO

I use a 2.5 foot 2 x 8 and plop it on the 3rd little step on the ramp.


use a couple foot piece of wood to get up the ramp without clearing off the spoiler, makes the ramp less of a sharp approach

[nizmainiac]

i do

[attack eagle]

Crossmember and diff for me. Been doing it for decades with no problem.
What I'm curious to know about is where people choose to put the jack stands.
In front I typically use the subframe rails, in back I usually go for the plate over the big bushing if I need the suspension to hang.

ditto, and I jack from the diff... had the entire touring lifted 3 feet in the air on the diff, with a block of oak between the pan and the diff. SOB is a 90lb chunk of cast iron, and probably the strongest part of the entire car.

if it will handle 4000+ lbs, you sedan guys are fine.

haven't had to lift the front end with anything other than ramps or the factory jack in such a long time I forget where I lifted it from when i had a lift.

[icesoft]

http://www.fp32.com/icesoft/e34/intogarage.jpg

Of course I was doing all kinds of work at the time (struts all around, new stainless exhaust, auto->manual swap, etc)... Since then the lift has become a place to store all kinds of stupid ****. I don't think it's had a car on it since then. :(

[Rick L]

NEVER! I noticed floor-jack pressure dent on my cross-member from previous auto repair shop. I always use the four point after seeing that.


Who jacks their BMWs on the differential and front cross tube?

[infurno]

http://www.autoblog.com/2008/09/02/pump-it-up-titan-air-jack-blows-itself-up-with-exhaust/

"Quite simply, the jack is nothing more than a heavy-duty balloon inflated by the exhaust gas of your own vehicle."

Interesting, but I wonder if its practical.