Transmission noise

[John Vyn]

I bought the boat in July this year. 3 months of safety and just plain fixing from the previous owner. Now I hear a clocking in the starboard transmission. Up to 2000 rpm trans is quiet, engines purr. At 2300 there is a mild slow click, over 2500 loud high speed click that can be heard over the engine noise. I have uncovered the engines and it's very appearant it come from the transmission. Am I in need of transmission overhaul? I am running 440' s with BW transmissions.

[Harry Babb]

I would not rebuild the transmission without first checking out other possibilities.

I cannot think of anything in the Velvet Drive, itself, that would make the Clicking noises that you describe.

My first thougths are the Drive Plate is cracked or broken, but they usually just rattle at idle.

At 2300 RPM there is nothing inside the engine or transmission that is going "Slow".......can you relate the frequency of the clicking with engine speed or shaft speed?

At 2300 RPM engine speed your prop shaft is probably turing just over 1500 RPM.

Sometimes sound sources can fool ya. I have used an extension from my socket set as a stethoscope to help pinpoint the EXACT location of a noise.

Have another question/thought......when you are hearing the noise, are you in gear running or in neutral (shaft not turning)

hb

[Charlie J]

my damper plates are getting a little noisey
going to put new ones in this winter

[John Vyn]

Harry and Charlie, thanks for the thoughts. I'll check more closely to make sure its the transmission itself. And the noise is very related to being in gear vs out of gear. My guess is the frequency is in the neighborhood of 200 hz at 2300 rpm and the frequency increased with rpm. The thought that it might be the damper plate (drive plates) is interesting. On my Grand Banks I had one break apart and seized the engine, but if just one spring were loose it could be hitting something when the centrifugal forces increase with rpm. Not easy to check, but there is a lead.

Thanks gents.

[Pete Fallon]

JohnVyn,
Sounds crazy but check to see how your spark plugs are, I ran 454 Mercruisers brand new engines in 1997, it set up a harmonic that sounded like the gears were going away. I had some bad Champion Plugs that made a awful noise at low speed in gear, changed plugs to NGK or AC the noise went away, cheap fix, however it sounds like your damper plates are getting worn.
Peter Fallon

[John Vyn]

Thanks Pete. I just put platinum plugs in within the past 20 hours as part of a complete maintenance of the engines. I did pull on plug and they don't look bad at all. I think I'm with you, it's the damper plates. Problem is the rear engine mounts are mounted to the transmissions, which means I need to prop up the engine before I can uncouple the transmission and bell housing to change the damper plates. I'm worried about the point load of a 4x4 post to hold up the rear of the engine. And of course there is not too much room to work on it. I may leave this to a professional.

[Harry Babb]

I'm worried about the point load of a 4x4 post to hold up the rear of the engine.

A small hydraulic jack sitting on a makeshift platform in the bildge and a 1x4 between the oil pan and the jack will hold up the engine just fine.....safely and without damage to anything

Or

Fabricate an "A Frame" over the top of the engine (Running bow to stern), using 2x4's, 2x6's and threaded rod, then use a small hoist to hold the engine AND have a lifing aid to help manage the tranny

hb

[Hyena Love]

I just laid a 4x4 beam across the gunnels. Then, used a chain fall to support the engine from the lifting eye while I removed the transmission.

[Harry Babb]

Sooooo......any word yet?..........just curious.

hb

[John Vyn]

Sorry Harry,
No word yet. I'm still trying to finish up the new fuel tank install, and use the boat around Newport Beach bay. Today I took the engine covers off and put them on the bow. Now I can pull the floor boards, tie off and pad all the fuel hoses, foam the tank in place, build a stern trough to route water on the deck out the skuppers, and put the cockpit back together. Right now I'm only running at low speeds and there is no noise. Hopefully I can get all this done this week and then tackle the transmission noise.

Thanks again for all the input.

[John Vyn]

Well I finally finished the tank and deck install. So I pulled the transmission. The damper plates were almost new. Looked new. No looseness in the springs, no debris in the bell housing. So I took it into our mechanic and he tore it down and overhauled it. I got it back yesterday and installed it. Today I ran the boat up to about 3200 RPM and no unusual sounds. There must have been something in the transmission that didn't like any RPM over 2300. Newport Harbor started our 106th annual Christmas parade last night and I only had to miss one day. Anyway, thanks to all who offered help here, and have a safe and Merry Christmas.

[Harry Babb]

Thanks for the follow up......always good to hear final results

hb

[John Vyn]

Yep I ran at idle for a couple of hours last night watching the parade with family members. All worked well and no leaks or troubles. On to the next challenge.