Bicycle Mechanics - Box full o' neutrals

Can anybody describe for me the symptoms of a dying freewheel? Tests?

My Trek 1220 runs Shimano RX105 hubs laced to Mavic Sup rims. Being a '94 model, the rear carries a 7-speed cassette. (The original rear rim disintegrated, as do ALL Trek Matrix rims. The new ones were laced up in 1997.)
The hubs have 17.7K miles on them.

For some time, I'd been hearing a clicking noise under load, only when I pedal, but I'd attributed it to one of the Performance Bicycle platform pedals (no big deal) or to the BB (I don't want to know.)

Well, the clicking has degenerated into a "graunchy," sound, in all gears, under even the lightest load... even when I backpedal... (!) almost as if the rear derailleur isn't adjusted properly... accompanied by a rather spongy feel in the drivetrain.

I was pressed for time last night, but I did do some investigating:

1) Pedals spin smoothly, although the right one does emit a faint click now & then. (That's my punishment for refusing to use clipless pedals, n'est-ce pas?)

2) With the chain pulled away, the crank turns smoothly and silently. No play.

3) With chain in place and backpedaling slowly, I can hear a faint "pop" at various points in the spin. The chain does not jump or bind as far as I can tell.

4) With the chain pulled away, I can back spin the cassette, and there is a faint "graunchy" sound there. Also, the cassette has a minute amount of side-side play in it, despite my tightening of the retaining ring last Sunday when I washed the bike.

5) Chain is a new-ish Shimano HG91, less than 1K mile old, clean and properly lubed, and the cassette was replaced with the chain.

I have a spare wheel assembly, from another bike. I shall mount a tire on it this weekend and try it out, but as I'm stuck at work right now, with no way to work on the bike, I thought I'd effect some virtual bench testing...

Maybe the internals in your freehub. The teeth of your cassette are too young to be worn down and the chain is also new.

I also refuse clipless pedals, but I've never regretted it. (Well, it bums me out when I lose the clip screws.)

By the way, nice frog. Didn't you used to be le bleu blanc rouge?

Serge,
I don't know if this has anything to do with your problem, but I would add a shim to tighten up your cassette. Having it shifting around could be part of the problem.
When I built a custom cassette a couple of months ago by turning a 12-21 into a 14-21, replacing the 12, 13 with the 14 and adding the 16 from a 14-32, I wound up with some slack because the 13 (second in the 12-21 stack, had a built in spacer. I just took a couple of the little cog separators out of the extra cassette to take up the slack. If you have an extra cassette lying around, you could give that a try to tighten up the cassette. Having slack there can't be good.
Regards,
Raymond

Thanks for the suggestions...

As Saturday is calling for rain, I will have time then to pull the wheel off and examine the freehub. Meanwhile, I have my trusty, rusty rainbike to use.

Yes, Oscar, I was B/B/R (cocorico!) until I discovered la grenouille icon. I could not decide which I wanted, but since the locals call me "froggy," due to my nationality, I thought I'd try her out for a while.

BTW, folks in Georgia, USA, pronounce grenouille as something like "granola," instead of a more acceptable "grun-wee."

I'm not really up on when everyone converted over from freewheels to freehubs, but in '94 maybe a couple of 'em were still being sold. Anyhow, it sounds just like a grungy freewheel.

If you have a freewheel cogset, you can take the whole thing off the axle, clean it by dipping repeatedly in the cleaning solvent of your choice, until all the grinding noise is gone (no need to disassemble anything). Then let it drain for a day or two, oil with a lightweight lubricant, remount it, and you're good 'til the next time. Be sure to grease the freewheel threads on the axle well before re-installing the freewheel.

I replaced the suspect wheel with my spare... noise and weird feel are now gone from the drivetrain.

The bad wheel's hub bearings are tight and quiet, but the freehub's ratchet mechanism sounds like a diesel truck at idle, and it is possible to ratchet it forward just a bit, which surely is not right.

So: Shimano RX105 rear hub, RIP.

This proves the value of keeping bits off of old bikes... one never knows. The replacement hub is laced to a very good Mavic rim, and came with a $20 bike attached to it. That the frame was wrecked bothered me not a bit. I stripped it down and binned the bits I didn't want.

Freehub mechanisms are replaceable and not very expensive. No need to replace the whole wheel.