JRas

I've decided to make this thread to attempt to educate people on the design of their cars. It's come to my attention that people don't know, that their cars DO NOT have an frame-rails. The 240sx is a unibody meaning all the structural strength is from the external skin.

to read more about this structural design I recommend reading the link below:
Monocoque - Wikipedia, the free encyclopedia



these long beam type things that come down the middle of the car are called side members as you can see from the picture. This is not a frame-rail like most assume.. these are not designed to be lifted from under any circumstance.

you may ask where should I lift my car from than? from the front cross-member or rear differential. Anywhere else, and you are risking the chance of damaging the chassis.

where should I place my jack stands? again in the picture it is shown and labled "Safety stand points" but it's not as specific as I'd like it to be.



the factory service manual recommends you use a saftey stand adapter on top of your saftey stand. this is basically a rubber block with a slit/groove down the middle. This slit or groove is where the pinch weld that run down the the sides of your car lays into. I recommend you find this adapter or get jackstands that are notched to properly seat these pinch welds.

I'm hoping you guys learned something and that I see less threads about someone damaging their cross-members.

feel free to post questions and comments

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SixSpeedSleuth

Thanks for posting this man. I work on my car in my garage and I have to use a floor jack and I've been putting Jack Stands under what I THOUGHT was the frame rail, which has been caving in a little bit. Hopefully I didn't mess with the structural integrity. Damn!

SexPanda

Or... go to a garage with a drive on lift. Most military installations with Auto Craft Shops (i believe most of them do) have drive on lifts. Either way good post. i've seen a few cars screwed up by lifting somewhere wrong, ie, crushing in a door. Dont ask, it happens.

Also, lifting at the pinch welds, if you have an in floor lift, is a good place too. Just watch out for exhaust, gas tanks, etc.

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driven_

apparently, some old guy lifted my car without me noticing it, and its a rustbucket, so the pinch welld near the front fender bent in straight up. -_-'

damn old people...

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LongGrain

yea, my pinch welds are pretty fucked from jacking on them.

the paint came off of one of them and now my rocker is rusting out pretty bad, gotta do something about that this winter.

driven_

shouldnt this be "aren't?"

i'm confused.

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driven_

crap milwaukee roads + salt + rusty rockers = no driving the 240 for me this winter

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racepar1

There is actually a little circular lift pad at the rear of the s-13's and you CAN use the "framerail" but DON"T JACK IT UP IN THE MIDDLE! Jack it up at the front of the rail just before it starts to turn up. That is a VERY strong part of the chasis. I lift tons of 240's using those points all the time and have NEVER damaged any of them. Jacking at the pinch welds is aldo a bad idea, but sometimes is necessary on very low cars.

EDIT: I place jackstands at the very front and the very back of the rail all the time and it has never done any damage either. Everytime I put jackstands on the "safety stand points" circled in your pictures they bend.

cc4usmc

no. he's saying that if you were to life from anywhere else but the rear diff and front crossmember you're risking damage.

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driven_

oh, yeah, i got it after i read it a few times

correction with punctuation:

" from the front cross-member or rear differential. Anywhere else, and you are risking the chance of damaging the chassis."

yeah, sorry guys, i'm a punctuation cunt, otherwise i no do the understanding of you.

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flip3d

i use the front of the rail where it looks reinforced.

the jack wont fit under my diff or under the crossmember

trogdor

ive been doing the same thing to 3 of my 240's...never had a problem with it caving in because it's reinforced. shops use these points for jack stands as well.

surreybc

the factory service manual calls front cross member the front suspension member.

i have used the round knobs at the back for lifting. they dont seem the right shape to accomodate jack stands.

very good thread

iluvpandas4

Good stuff, I'm gonna print this out and show it to my buddies when I tell them to jack up the car.

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dynamicck

good post.
too bad im too lazy to make or find a pinch weld pad.
I've seen them like once being sold in a stock. 99% i end up bending the pinch welds.

I've known a few people who've made their own jack pad by using a block of wood, and cut a groove for the pinch welds.

ericcastro

i actually use the force to lift my car.

I understand that mainly the Premium members here have the access to those kinds of abilities.

But over time anyone can achieve it.
Lotsa practice, patience, elbow grease and some time.

Otherwise, just use the Jack Points shown above.

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champagnes13

i drive the car onto 10" long 2x8s. it brings the car up high enough to get the jack under there.

burnsauto

yeah my pinch welds are completely shot...some metal work needs dont this winter to fix the "frame rail" rot on the driver side, and fix those damn pinch welds.


grr.

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kevtrinh

i just lift them from the tow hooks

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cwd240

lol i just found that funny


good write up, I always wondered where to properly lift the car

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SexPanda

By floor jacks, I should have said floor lifts. Those in ground lifts you drive over...

Firestone had them when I worked there. They lifed up evenly all the way down the pinch welds. Worked great.

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surreybc

You can find the jack stand postion by the notch in the seam(pinch weld) that runs from wheel well to wheel well. the position is few inches from wheel well on each end. not sure if my jack stands are suitable or that i would trust since the side member has worked. I assume the stand straddles the seam.

Mangudai

So its not a good thing I have the front of my car up right now by the way of two jackstands under the crossmember?

firelizard

lol

Earlier today I put my car on jackstands.....


on the "frame rails"

I knew they weren't actual frame rails, but they looked more solid than the rockers. Guess I have to rethink this tomorrow.
Repped for good and important info!

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surreybc

if you dont have suitable jack stands it might be better to continue doing it with side member where it is strongest.

murda-c

I always hated when i was at work and a car would come in with pinch welds that weren't mangled, cuz then you have to take care to use the right adapter so you don't fuck them up.

(or just jack the car by the "frame rails")

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xkamikazestormx

since my car is insanely low, i just use my small jack to jack it up from the tow hook and get the big jack to jack it up from the diff.

for the front, i drive up on ramps/2x4/etc to get my front end high enough to fit a jack underneath the front crossmember.

jackstands for the rear i place them where the subframe U's. right by where the toe rods connect to the subframe. for the front, i place them underneath my flca

boske

Whats wrong with jackstands under the crossmember? Thats labeled as a jacking point anyway. Don't try putting jackstand on the framerails right under the seat area, my floors pushed up from it now, framerails are all flattened

JaeTea

I'm almost positive that the FSM states to lift the car from those points, if you're putting it up on a lift.

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Def

I'm pretty sure there is a diagram in the FSM that states the front/rear of the "framerails"/crossmembers being the preferred place for putting a jackstand.

There's no way I could ever jack my front subframe, and my car isn't even that low.