Bob Lang wrote:
> I've done the test that Paul R. suggested on the TR6... a strobe does
> help to see the problem, so if you know someone with an assym. lift that
> has a strobe - you should be able to run the car up and see the vibration.
>
> I've done this on jackstands in my garage - def. not recommended unless
> your insurance is paid up! I didn't have a problem, but the thought of
> the car falling with the rear wheels already at 70 or so makes me shiver.
Besides being careful as to jack placement, you also want
to try and keep the geometry of the drivetrain the same as
it is when on the road. That's easy for solid axel cars as the
jack stands can be placed under the axel.
On IRS cars, if you place the jacks under a frame you end up with
the rear wheels being in extreme angles and this may cause
real problems in doing the test.
I had a driveshaft vibration problem on my TR-8.
Doing the jack stand test showed severe vibrartion
at about 50 mph plus. I opted for one of Ted
Schumacher's TR-6 converted driveshafts and haven't had
a problem since. When installed on the car, I
ran the test up to 100mph with no vibration at all.
To be sure, from a safety perspective,
had I encountered any vibration with the new driveshaft
a lower speed I wouldn't have run the test up to 100mph.
The problem with the TR-8 driveshaft was the rear
CV joint which virtually renders the driveshaft as
useless since it isn't a rpaorable item. At the time
(about 8 years ago) the cost of a new TR-8 driveshaft
was over $450. Cost of Ted's converted TR-6 unit
was under $200. It was a no brainer for me with
improved serviceability since the converted driveshaft
now has simple U-Joints rather than non-replaceable
CV joints.
> I'd also suggest having the prop shaft dynamically balanced.
Especially if the problem isn't with a CV joint prop shaft.
Checking the balance may show something way out
of balance which is the problem.
Cheers,
Bill Sohl
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