It was almost a month ago when I wrote about this problem.
T-list members were generous with suggestions and sympathy. Among the
suggestions were: pilot bushing (we replaced it, firt is good), throwout
bearing (6,000 miles old and inspected again by John Esposito), thrust
wear in engine, worn universals (knocks w/o driveshaft connected), clutch
loose (tight with 31 ft/lbs torque on all capscrews), starter loose &
rattling (it's tight), engine mounts ( all new), loose connection bell
housing to engine ( all holes since helicoiled and all capscrews are
pulled to 31 ft/lbs). Another friend pushed and pulled crankshaft pulley
and pronouced thrust movement OK (6000 miles on engine since a Wanta
rebuild and there was no knocking before this R&R of gearbox).
We have run the engine with gearbox removed. It's purrs nicely. A
stethescope picks up no knocking in the engine.
Gearbox turns silently, smoothly, both by hand and at 1000 rpm under
drill power, shifts well.
Clutch pedals have normal but not excessive wear in holes and rest of
linkage is OK.
Any other ideas ? At this point we are keeping careful watch to see
if it's space aliens tapping on the metal, or some tiny creature trapped
inside.
On the bright side---we're getting quite proficient at R&R of the
gearbox.
Bob
On Mon, 27 Nov 2006 09:33:06 -0500 Bob Howard <mgbob@juno.com> writes:
> A request for advice....
> Last summer a club member had troubles with his TD gearbox. He
> removed the gearbox and sent it out for rebuilding by Quantum
Mechanics,
> John Esposito. What with parts availability problems, it was not
> returned until a month ago. I helped reinstall clutch and gearbox.
> When the engine was fired up, there was a hollow clunk/clonk sound
> at engine speed to the rear of the engine. As the engine had been
> rebuilt two or three years, approx 6000 miles before, and it was
running
> nicely before the gearbox removal, and the sound stopped when clutch
pedal
> was depressed, our assumption was that the problem was clutch or
> gearbox related.
> We removed clutch and gearbox Saturday and took them to John for
> another look. He interrupted his work to inspect clutch pieces
> with magnifying glass, opened gearbox, fished around inside with a
> magnet, drained the oil and inspected it thoroughly, turned gearbox by
hand
> while listening and feeling carefully, then turned it with an electric
> drill. Gearbox and clutch were found to be in A-1 shape. Clutch and
> throwout bearing are also 6000 miles old.
> We reinstalled.
> The clunk/clonk is still there, perhaps worse than before. To our
> ears it seems to be inside engine at the rear, a dull hollow sound as
if
> one tapped the bell housing with the plastic end of a screwdriver, not
> a bright sound as if one tapped it with a hammer. It stops when
> clutch pedal is depressed.
> Oil pressure is OK. Oil level is OK. Owner changes oil regularly
> and keeps up maintenance. He's not rough on engines; a Porsche daily
> driver has 250,000 miles on it with only normal clutch and brake
> replacement being called for.
> Sound seems to be the same volume and tone at idle up through
> 2000 rpm when it disappears in the other engine noises.
> We adjusted valves on the off-chance that one might be very
> loose--all were OK and noise did not change.
> What might the problem be?
> Bob
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