At 09:46 PM 5/14/2001 -0400, Christopher Marley wrote:
>....
>1977 MGB. .... When I shift there is a short period of a second or two in
first gear when there is a grinding clunky sound from the underneath and
front of the car. .... I have had the transmission rebuilt ...., the clutch
rebuilt .... And how much noise is normal in an MG.
As the gearbox has been rebuilt, it should not be any problem with 1st gear
syncronizer. However, if you have a broken tooth on ist geat you would get
a cyclical clicking noise that starts slow and increases in speed
proportionally with ground speed.
More likely you have a clutch problem. If you have a rebuilt clutch disk
with worn internal spline, or a badly worn gearbox input shaft spline, then
the clutch disk can orbit slightly on the splined shaft, which generally
yields a low pitch squalk while the clutch is partly engauged.
If your recent work did not include replacing the pivot bushing and/or
pivot bolt for the clutch release arm, then the release bearing could be
off center and rubbing on the gearbox input shaft, usually a soft whiring
sound, or the arm could be wobbling around in resonant fashion making a
chattering sound.
However, clutch problems are often the same in each gear if you let the
clutch pedal up slowly with light to moderate throttle setting. If it's
clutch noise only in 1st gear, then it's speed sensitive, happening only
from a dead stop up to very low speed on the gearbox input shaft. Once the
car is in motion, shifting gears never stops the input shaft or slows it to
very low speed.
Another problem which may occur only in 1st gear could be the engine
rocking on the rubber mounts with the applied torque. The torque that
rocks the engine is a reaction from the tourue of the propshaft, which is
greatest in 1st gear. If the engine mounts are very soft or broken (common
with the lated MGB with the round engine mounts), then the engine can move
around too much, and the exhaust header pipe could be touching and
vibrating against the frame or steering column.
Lift bonnet, start engine, idle in neutral with parking brake on. Stand
near left front fender, give throttle cable a sudden pull to full open
throttle for a half second, adn observe the rocking motion of the engine.
The top of the valve cover should move sideways no more than about 1/2
inch. If it moves farther you probably have bad engine mounts.
Otherwise, please explain better what is "a grinding clunky sound".
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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