Bearings howl and gears whine. Bearing howl will occur all the time. Gear
whine will occur only at specific speeds, and/or in specific gears, and
only when under load.
I think what you're experiencing may be a clearance problem, probably
between the exhaust or its heat-shields, and other parts.
Remember that engine braking on a manual, especially from high-rpm in the
lower gears, causes the engine to move quite a bit on its mounts. Should
the exhaust contact the body (or should the shift rods contact the
exhaust), you'll get some pretty awful noises and vibration. Check
carefully for shiny spots or other signs of interference on the shift rods,
the body, and the heat shields.
Does this thing have a short-shifter, aftermarket exhaust, or other
modification from stock?
but gears can whine when bearings are out, not because the gears
themselves are a problem. for instance, with helical gears there is
axial loading. if that causes axial bearing load in the direction of a
good bearing, all will be good and silent - in the reverse direction
where the axial load is on a bad bearing, all hell breaks loose.
exactly what we're experiencing here. i'm trying to figure out which
one is the likeliest and buy a replacement before removal of an
otherwise perfectly serviceable transmission that's not giving any metal
filings on the drain magnet.
subsequent to my post, i found an article by mistabone on this problem
and he says it's input shaft closest the flywheel is the commonest
failure. however, he then goes and ruins it by advocating the use of
"staking" bearings in place with a punch. really really really not a
good idea - fatigue crack initiation. if there's a bearing retention
problem, you should use an appropriate loctite retainer. easy to
assemble, and local heating makes it easy to disassemble. do NOT punch
fatigue initiators into your aluminum gear housings you crazy kids!
yeah, we're looking into that too - it's raining out so i'm not lying on
my back in that stuff if i don't have to.
yeah, aftermarket exhaust. i'm going to let the car's owner worry about
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