I think this detailed reply is important for all listers who are interested
in this subject to read for themselves and to make individual opinions (and
subsequent decisions?) based on the points made.
> At least you offer food for thought and an opportunity for users to make
> a decision for themselves... and maybe those with factory technical
> information at their disposal could try to look up such engineering
> information. Maybe someone who has access to Triumph service >bulletins
could find something regarding this.
I hope so. My source was an Engineering Procedures Manual and this
publication was usually only for internal use and not for network release.
> The original post that started this thread suggested that jacking the
> car would potentially thrust a mounting stud through the cross
> member... I debated this...and would again.
> A following post suggested that the bushings were not "designed" to take
> such a load... and I debated this and would again.
> I would suggest that anyone with a manual, or a stripped IRS frame
> sitting in the garage... look at the IRS layout... and study what would
> happen when you lift the differential... remembering that the car
> weighs 2240 lbs.... I would assume less than 1/2 of that at the rear...
> In my opinion... The load is well spread across two separate cross
> members attached to the frame. The load is not placed on the mounting
> studs. The bushings are solid and are not going to be damaged. The IRS
differiential casing is quite a solid piece.
> And lets not forget... when you jack one side of the frame at a time...
> this is ALSO putting loads on the very same cross members. Jacking a car
is going to put strains on the frame...
> > The only area that now makes me uncomfortable... having put increasly
> more thought into this due to the thread... is my assumption that people
> would have solid frames.
Not necessarily so. OK, solid when the car is new but rear end chassis rot
is common in countries where heavily salted roads are an inevitable winter
hazard.
> I've held the opinion that if jacking the car by the diff should break
> the mounting studs... or, for that matter, any of the cross members...
> it would be a good thing... because it's better to know now, than while
> driving... (If it should give way while jacking, it's not a safety
> issue, as suggested by Gernot, because A. you're not under the car while
> jacking it up and B. even if one of these items snaps, the car would not
> come crashing down.) ... but living in California, I tend to forget that
many of you have IRS frames that you could put fingers or even hands
through the rust holes...
> And while it is easy for me to say, "hey, if your frame is so screwed up
> that jacking your car is going to cause it to snap... then it's time to
> do a frame off and fix it..."
> Well... I suppose... while it's not safe to drive on rotting frames...
> maybe it's just something you've got to do... if you're going to enjoy
> the car at all... While I would enter, you're not only placing yourself
> in danger, but those around you... particularly those in the path of
> your moving car...but, generally, when things like mounting studs
> give-way... it leads to a clonk or a thump, rather than an accident. (I
> would hope you would inspect the critical areas regularly, and beef 'em
> up when necessary!)
> Having heard all the threads... if your frame is borderline... or
> worse... by all means... avoid the diff... Maybe you'll get a few
> more miles. Particularly if you baby it up, as suggested by Steve
> Chandler, with TWO jacks being raised relatively simultaneously.
> Or just avoid the differential altogether, because John's having had to
> write it down 100 times for his headmaster-mechanic, has weighed your
> opinion against it. At least it would be a decision based on some
> reason.
> (So there's no confusion here, I never suggested you LEAVE the car
> supported by the diff... the idea was that you could jack the
> differential up with a floor jack, and then lower the car down onto jack
> stands on the frame rails! There may be a "cross the pond"
> misunderstanding in english... as the term "jack", etc., has different
> meanings, I recall.)
Yes, it does. But in this context it's the same.
> I would like to hear from qualified sources, specifically where/why
> damage would be done in lifting a TR 4A/TR 6 type rear end by the
> differential...so that I can look at it for myself, and come to
> understand it. I enjoy such input.
> The point of all my posts regarding this matter have been based on the
> following premise:
> Disinformation should be routed... through informed debate... to give
> readers the opportunity to determine what is right for them, without
> being prejudiced by misguided theories, particularly those that incite
> fear.
> I simply felt visions of damaged bushings from an occasion car-jacking
> and mounting studs breaking through the cross-member were not
> warranted...
> And any post that would suggest that I am blind to safety concerns is
> not warranted, nor appreciated.
If I have given the impression you are blind to safety, then I apologise
because that was neither considered nor implied. What I was trying to point
out to owners/users (of which there are clearly many who seek help and
comment) is that such a procedure was actively discouraged by the vehicle
manufacturer itself.
It was a well-known fact within Triumph and the whole of its global dealer
network that chassis rot was an unacceptable fact of life. Attempts to
combat its effects were rather unconvincing. That said, I doubt any
manufacturer would preface even an internal publication with such remarks
or even allude to it in the most oblique way.
In the final analysis, raising a vehicle off the ground must be dictated by
the available equipment, operator skill and the likely damage that might
result from such actions. All I would add is that if the diff carrier
within the chassis assembly is suffering the effects of long term salt
corrosion, (and in some cases just 3 years of mild UK winters when compared
to those of Scandinavia and North America was sometimes
enough) this damage may not be visually evident from below. It usually
affected the upper part and was often accelerated by torque load/unload via
the diff.
I entirely agree this issue is something which must finally be decided by
listers based on reasoned debate, the evidence of their own cars and their
own inclinations. I also feel that fear should not be disregarded - whether
it comes from the possibility of a car falling through frame collapse or
the cost of undertaking expensive repair. Finally, if I am able to impart
what is effectively inside track knowledge from more than 30 years ago to
aid a decision (one way or the other) I am happy to impart it in
everyone's best interests and let them make up their own minds on the basis
of all available comment and opinion.
John Macartney
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