Milo,
> I'm sure it an engine vibration because if I let the car out of gear but
keep the
> engine revved at highway speeds, the vibration goes away.
I think this proves that it is *not* an engine vibration. I think this
strongly suggests it's something in the driveline that shifts or deforms
when it's under load. Most likely, I'd say a u-joint. But you can keep
yourself awake at night wondering if it's a worn pilot bearing allowing the
tranny input shaft to shift slightly out of alignment. Maybe a flywheel
bolt's coming loose. It could certainly be the u-joint carrier coming
loose from the transmission output shaft or from the differential input
flange. (Man, don't you reckon it would make a mess if one of those
flanges ever just let go at speed?!) I've had transmission mounts loosen
up on me. I've even heard of bellhousings loosening up (but that was on a
sensible FIAT with only 4 bolts, not an anal-retentive TR with 4-dozen...).
Maybe the bailing wire you threw in the passenger seat worked its way down
to where the unsecured transmission cover flops around the handbrake; then
a loop of bailing wire got caught on the driveshaft and pulled the whole
roll down, wrapping itself unevenly around the driveshaft...
> Could someone let me know what they think the most logical approach to
> solving the problem is, or possible solutions?
Grab a handful of 1/2-inch and 9/16 spanners and crawl under the car
========================================================
Obligatory warning:
Always support your car on 4 sturdy jack-stands before you crawl under it.
Use only the strongest, best quality jack-stands on the market. *Never*
crawl under your car if it's only supported by a hydraulic, ratchet, or
screw-jack, by cinder blocks, or by lumber. *Always* test the stability of
your jack points by shaking the car before you crawl underneath it. If
this makes you nervous, don't work on the bottom side of your car. If this
doesn't make you nervous, *definitely* don't work on the bottom side of
your car.
========================================================
and make sure everything's bolted up tight. If it's a j-joint that you
don't feel/hear until 3500 rpm, you won't be able to see or feel any slop
by examining the part on the car--but just for shits and grins, wiggle all
the u-joints vigorously (you tested the jack stands, right?). Any
detectable play is unacceptable (OK, it's your car, so you define
"acceptable"--but if you can see/feel/hear play with the car on the ground,
you'll definitely feel/hear it on the road).
Anyway, if you haven't done the clutch and u-joints on your car in a while,
just tell yourself you had it coming and spend a weekend replacing them
all. I'm fairly certain your problem's in the driveline, between the
engine and differential, so I won't get imaginative about other places to
look.
Or then again, of course, you could always just slow down...
Kevin Riggs
'72 TR6
rkriggs@ingr.com
Huntsville, AL
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