Transmission Noise

billbalme · #1 08-17-2009

Toodle-oo! has developed a chirping noise in the transmission. Not sure where, not sure how to diagnose it. It crops up for a few seconds initially, but can last a while when the engine is pushed above 1500rpm.

As an aside, I called the local guy - left a message telling him that I had the noise could he give me a call. I identified it as transmission vs. engine -since it only occurs when in gear. I get a voice mail from him a couple days later asking me to call - but I didn't - since I was going to be taking the boat for a few days, so wouldn't be able to schedule any time on the boat with him. I arrived back after those few days to a bill for $100 - "Customer complains of noise in transmission - diagnosed as faulty transmission." Whoaaa!

Anyway... how DO you isolate the noise? I'm guessing it's the gearbox, but could it be the cutlass bearing, stuffing box or something else? Fearing the worst, how difficult is it to fix/replace the gearbox?

I think mine's a Hurst gearbox - is that good or bad?

Bill
s/v Toodle-oo!

JohnRPollard · #2 08-17-2009

Bill,

I would suspect the stuffing box first, especially if you recently fiddled with it. The noise you describe sounds vaguely familiar to one I once heard after tightening the SB too much.

P.S. Did that guy actually come out and inspect the transmission, or was the $100 bill for a "telephone consult"?

billbalme · #3 08-17-2009

I'm embarrassed to say that I've only once touched the stuffing box, and ended up not adjusting it - and that was last year sometime. I guess I need to count drips (as is being discussed in another thread).

I hope he came out to look (though I did not detect any evidence that anyone had been aboard ) because we've never actually spoken about the problem! What a racket!
I left him a voice mail last night along the lines of: if he gives me a full diagnosis of what's wrong and an estimate of what it'll take to fix, I'd pay the bill - otherwise... (I think that's fair isn't it?)

JohnRPollard · #4 08-17-2009

Quote:

Originally Posted by billbalme

... I hope he came out to look (though I did not detect any evidence that anyone had been aboard ) because we've never actually spoken about the problem! What a racket!
I left him a voice mail last night along the lines of: if he gives me a full diagnosis of what's wrong and an estimate of what it'll take to fix, I'd pay the bill - otherwise... (I think that's fair isn't it?)

More than fair.

orientalnc2010 · #5 08-17-2009

Quote:

Originally Posted by billbalme

Anyway... how DO you isolate the noise? I'm guessing it's the gearbox, but could it be the cutlass bearing, stuffing box or something else? Fearing the worst, how difficult is it to fix/replace the gearbox?

I think mine's a Hurst gearbox - is that good or bad?

Bill
s/v Toodle-oo!

Hi Bill,
If you suspect the noise is in the gear box you can use a very large screwdriver as a stethoscope to try to isolate the noise. I would only attempt this while the boat is securely tied to a dock, put the boat in gear and get the RPM up past 1500. Carefully place the blade of the screwdriver against the gear box and the plastic end against your ear, if you are not comfortable working around the spinning prop shaft or cannot find a solid spot to work from do not attempt it. One slip and you can imagine the consequences.
I work on elevators and have had great success isolating scrapes and noises that seem transmit in all directions.

BMLipiec · #6 08-21-2009

Bill,
I doubt your problem is the same as mine, but I recently had a rattling problem that I thought was coming from my transmission on our PSC 34. It only did it when I shifted into forward at low speed and it sounded as if something was going to shake apart, and would stop immediately when I shifted it into neutral. However, it turned out to be a loose nut on one of my engine mounts. When I shifted into forward, the torque on the engine would lift that side off of the mount enough to cause the lock washer to rattle loudly. It took awhile to diagnose because I was sure it was the transmission and with the engine running it was hard to pin-point where the rattle was coming from.

billbalme · #7 08-21-2009

This week as we were preparing for the club race (now there's another story...) one of my crew took a swim around the prop. It was loose. He tightened the nut and replaced the zinc - which had disappeared. Naturally, we all thought the problem would be fixed - but alas no. Unfortunately no time to diagnose the problem, but he and I both agree that the noise sounds minor - and perhaps it is something loose - maybe shaken loose by the wayward zinc and prop. I'm REALLY surprised the prop came loose - and wonder if it did so because it's now solid copper - no longer bronze!

The difficulty is knowing how to find the noise. I shall try the long screwdriver approach and I'll check engine mountings... I'll be hauling the boat pretty soon anyway - maybe we'll find it then if not before.

Appreciate the ideas...

k1vsk · #8 08-21-2009

It could be a number of things folks have already suggested or, if it occurs when you initially shift into gear, it may well be the damper plate going bad.

billbalme · #9 08-22-2009

The noise doesn't come immediately when I put it in gear - it normally takes a few seconds...

I was hunting for it again today - nothing obvious. The stuffing box is pretty wet - needs tightening, but I didn't do it today (I need Calder before I attempt something I don't know how to do) - could that loose stuffing box be it?

I inspected the prop following my friends efforts - the prop is scarily clean - suggesting that the zinc had been gone for a while. The prop was at least secure, and I couldn't feel any movement in the cutlass bearing (not sure if one would).

JohnRPollard · #10 08-22-2009

Quote:

Originally Posted by billbalme

...could that loose stuffing box be it?

I wouldn't have thought so. In our case, we had over-tightened it.

Merely tightening the stuffing box is pretty simple -- no need for Calder on that (he'd be good to have for re-packing, though). All you have to do is back off the lock nut a bit, then tighten the packing nut a 1/4-1/2 turn, then snug the locking nut back against the packing nut.

You can do it!!