> spinning the
> driveshaft without the gears spinning is rotating the shaft
> inside the gears at a speed equal to the road wheel rotation
> speed divided by you rear end ratios IE: the turns per mile
> on your speedo face, revolutions every minute at 60 mph.
Don't mean to be picky, but the driveshaft rpm is actually road wheel rpm
_times_ the final drive ratio.
Also, the speedometer cable is driven through a substantial reduction (5:2
for TR3), so it turns quite a bit slower than the driveshaft as well.
> So example....after 500 miles ~ 8 hrs @ 60mph w/ 3.90 rear
> roughly 1000revs per mile = 1/2 million revolutions of the
> shaft with no lube!
TR3 driveshaft turns approx 3000 revs per mile, 1.5 million revolutions in
500 miles.
(Easy way to verify: check your tach reading at 60 mph in 4th direct. 60
mph is 1 mile per minute, and 4th direct is 1:1, so revs per minute is how
far driveshaft turns per mile.)
All on a tiny bearing that normally only turns in lower gears and neutral,
normally with a generous supply of oil.
I once bought a wrecked TR3A that had apparently been towed with the rear
wheels on the ground. The tip of the mainshaft was dark blue, indicating to
me that it had been badly overheated and the heat treat ruined. It had not
failed yet, but it seemed clear to me that it would have failed in the near
future.
Somewhere, I've still got the input shaft, which was also discolored around
that bearing. It's good for aligning clutch plates, but useless as an input
shaft.
Long time ago, I subscribed to "Motorhome Life" magazine, where this exact
problem was often discussed. Several imaginative solutions proposed,
including an electric pump that pulled oil from the drain plug and sprayed
it back through the fill plug. Overfilling was a fairly popular option as I
recall.
I'll also point out that the TR3 is not a particularly good candidate for
flat towing in my experience. The front suspension has no caster, which
means it doesn't like to follow the side forces when the tow vehicle makes a
turn. The front bumper supports aren't nearly strong enough to handle that,
even on a TR3A where they tie into the front apron.
BTDT, burned the T-shirt
If you want to flat tow, you're going to have to make up a tow bar that
reaches back to the frame, and is strong enough to handle the side forces.
Also, I flat-towed a mid-size Chevy for quite a few years. (It had a FWD
transaxle that lubed with only the output spinning.) I can't prove cause
and effect; but the "crossmember" in front of the engine broke clear
through. That car had a lot of flaws, but I never saw another one in the
junkyard with that same failure.
-- Randall
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