civic manual transmission question

if the transmission works noiselessly going forward, but grinds on over-run, especially in first and second, is that usually the input shaft bearing or one of the others?
don't usually deal with manuals and would prefer to target replacement based on others' experience before stripping it down to inspect.
thanks much
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nomina rutrum rutrum

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How do you define "over-run"? You mean shifting down to a lower gear?
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Tegger

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On 05/17/2010 03:12 PM, Tegger wrote:

taking your foot off the gas but leaving it in gear - engine braking if you like. makes noise thusly in 1st and 2nd.
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nomina rutrum rutrum

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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?
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Tegger

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On 05/17/2010 06:27 PM, Tegger wrote:

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 that stuff.
thanks tegger
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Yeah, and that's when they howl. I've heard it often enough.

Check out mechanical interference first. I suspect there's nothing wrong with your tranny.
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