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Re: New lister, query on TR6 jacking

To: Justin Wagner <jmwagner@greenheart.com>
Subject: Re: New lister, query on TR6 jacking
From: Steve Chandler <chand@primenet.com>
Date: Sun, 05 Apr 1998 18:46:29 -0700
Cc: triumphs@Autox.Team.Net
Organization: Chandler-O'Bagy Associates
References: <199804042034.VAA31429@andromeda.ndirect.co.uk> <3526AE37.5F03@greenheart.com> <3527A6CC.123C791@primenet.com> <3527F35B.4674@greenheart.com>
Justin Wagner wrote:
> 
> Steve...
> 
> Have you ever held one of those bushings in your hand?  Have you ever
> looked at a IRS frame, with the body off?

yes and yes.

> 
> How can you say they're "not designed to carry this sort of weight".
> 

Because it is not uncommon (especially on the PI models) for the
front right bracket to shear under the torque effect on the
differential.


> 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....
> 

They dont mount them with garden-hose washers and they still shear,
it is the torque effect that causes problems.


> 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.

It does'nt matter how long it is jacked for, it still weighs the same.


> 
> 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...
> 

It may be misplaced, but the chassis rails are stronger, and that's
why I recommended that method.


> 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

-- 
Steve Chandler - Chandler-O'Bagy Associates stevec@rtd.com

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