Steve...
Have you ever held one of those bushings in your hand? Have you ever
looked at a IRS frame, with the body off?
How can you say they're "not designed to carry this sort of weight".
Think about the sort of strains those bushings encounter when you throw
down that gas pedal! And with your outer axles thumping up and down and
your drive down a rough road... No, it's not a live axle... but if the
differential weren't encountering strains... they would have mounted
them in garden-hose washers....
When you're jacking a car... it's a gentle slow process... Those
bushings can handle it... the load is spread amongst 8 thick solid
bushings!!!! the structure can handle it... it's the same piece of
steel that handles your springs and suspension!!! And once the car is
in the air, it's put on jack stands... so it's not even being kept on
that weight for very long.
Honestly, I would just let this ride... but when I think of some
percentage of the newsgroup falling for some misplaced theory about the
dangers of jacking a car by the differential... I feel a need to say
something...
If you have two jacks... and no floor jack... by all means... jack up
the outside rails... as you suggested... but if you have a floor jack...
(every shop should have one)... and you'd rather spend time working on
your car, than jacking it... just jack the diff and lower the car down
on a pair of jackstands... and be done with it.
--Justin
Steve Chandler wrote:
>
> I have to disagree with your theory here. When you lift a TR6 on the
> differential you are compressing the bushings which were not designed
> to carry this sort of weight. I dont know if the mounting are strong
> enough or not, but the bushings will certainly be abused by this.
>
> Also I do not know how you can say this is less stress than driving
> the car. This is not a live axle, there is very little stress on the
> diff itself when driving.
>
> I would still recommend jacking up on the chassis rails with a piece
> of wood between the jack and the frame, and if you have 2 jacks do
> both sides at the same time, to minimize frame twisting.
>
> Not a flame, just my $0.02.
>
> cheers
>
> steve
>
> Justin Wagner wrote:
> >
> > jonmac wrote:
> > >
> > > John
> > > Many people use the diff for lifting as it is central. That does not mean
> > > it is a wise thing to do. There's a risk you might pop the diff mounting
> > > bolts through the top of the chassis....(snip)...
> >
> > I would differ with you on this...
> >
> > When you jack up the differential... you are NOT jacking up the mounting
> > studs... you are jacking up the BUSHED differential... which spreads the
> > weight across the structure very nicely... with little stress on the
> > studs themselves... In edition, there is not much SHEER strain on them
> > when lifting.
> >
> > The stresses encountered by the differential and it's mountings, while
> > jacking, are far less than anything they encounter on any given drive
> > around town, with speed bumps and potholes... If jacking your car by the
> > differential causes a mounting stud to "pop" through the chassis...I
> > would say, "BETTER TO FIND OUT NOW, THAN WHILE DRIVING AT SPEED, ANd
> > HITTING A BUMP"...
> >
> > Jacking "side to side"... takes time... and I would argue, the more
> > messing around one does while jacking a car exposes you to more
> > danger... and it is human nature that people will tend to try to speed
> > things up, by going up in higher intervals... leaving one side of the
> > car jacked up inches higher than the other...
> > Which again... exposes you to yet even more danger... AND... for those
> > concerned with damaging there car... this does put a lot of strain on
> > the car when flexed like that.
> >
> > I've jacked up TR 4A's, in the rear, with floor jacks under the
> > differential since 1977. I never experienced a broken stud... (on my
> > IRS) about 8 years... nor do I have any problems with my solid axle
> > 4A... (When IRS studs snap... it's because they're rusty and/or already
> > have a stress fracture, etc.) And my brother and I, the mechanics in
> > the family, have jacked up the family cars over the years... 280zx,
> > Jensen Heally, Jaguar XJ 6, Corvette Stingray, Mustang Mach I, 280 zx
> > Turbo, TR 7, Camaro, Ford LTD. Station WAgon with 429, and more... all
> > by the rear differential.
> >
> > Jacking by the differential is safe. Safe for the car, safe for the guy
> > under the car. My humble opinion... others are welcome to comment.
> >
> > --Justin
>
> --
> Steve Chandler - Chandler-O'Bagy Associates stevec@rtd.com
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