Velvet Drive Trouble

[MikeD@Lightningshack]

Guys,

454's with 1.52 Velvet Drives.

I changed the oil in them two weeks ago and the transmission coolers two years ago. I went out fishing last sunday and when I got back to the dock I noticed a rattling sound while putting the port engine it in and out of gear. I checked the oil and it was a little low... I added about 1/3 of a quart and the rattleing sound went away.

This weekend I took her out and while running at about 2400 RPM's I noticed the RPMS started to come up to about 2600. I shut her down and checked the oil again. There was plenty of oil, in fact a little too much, so I siphoned out the excess.

Bottom line is that I am pretty sure I need a new Velvet Drive. My questions are...

How much do they cost?
Can I buy a rebuilt unit?
Where can I get one?
Does anyone have one that they want to sell?

[Tony Meola]

Mike

Make sure the noise isn't from a loose prop. About 7 years ago mine did basically the same thing. I am in NJ, and we pulled out the transmission and had it rebuilt by Mack Boring. That was about $1200 back then. I got lucky, mine quit at the in September so we just pulled the boat and left it out for the winter. Tony Meola

[Charlie]

I would not be to quick to write off that tranny just yet. Ratteling at idle is common. If the tranny fluid does not smell burnt then I would say take another run or two. If the tranny is slipping the fluid will smel burnt and turn from red to brown or worse.

[MikeD@Lightningshack]

Guys,

Thought about things for a while, and wondered if maybe the tachometer could have been on the fritz thus making me think the trans was slipping.

Took her for a run tonight, tapped the gauge a few times, and never noticed any slipping at all. Checked the tranny housings with infrared gauge and both were about the same 120F.

Ran her for about an hour, hitting WOT twice and this never flustered the tach or the temperatures.

An extremely remarkable coincidence for the Port Tach to act up just after I changed the transmission oil, and after somehow leaving the port trans a little low causing the rattle sound, and putting me on high alert for a problem, but none the less, this seems to be all it was.

Mike Dolan

[MikeD@Lightningshack]

PS
Thanks for you help and suggestions

[Bruce]

Mike,
BW inline gears will not rattle even as they lose fluid. They will just get to the point where they start slipping and won't drive anymore as the pressure will drop causing the forward or reverse piston to relax allowing the plates to slip.

The way the reduction is set up is you have three small gears on the clutch shaft rotating inside the larger planetary gear on the output shaft.
This is a noise free type of drive even if run dry unless excess wear is present and that is very rare.


BW offset gears will rattle at idle due to the way the gears are cut verses the input rotation and play between gear faces.

Make sure the noise is not comming from the drive plate springs.

[MikeD@Lightningshack]

Bruce,

The rattle I heard could maybe described better as an unfamiliar clanking during the transition of gears, but not neccessarily while in gear or neutral.

After adding the fluid it definetly went away, but while it was happening I noticed the clanking/rattle from the bridge as I shifted the gears. I can only say for sure that it was prevelant while shifting into foward, as soon as I recognized the noise I checked the oil level.

Being unfamiliar with the design of these transimssions, and considering what I've explained in this post, should I even worry about the drive plate springs, if so how do I inpsect the drive plate springs for noise?

I do have stethoscope, but I am not sure what or where I should be listening to...

anyway,
thanks for the reply

[Bruce]

Some older bell housings had a rubber plug in the top.
This can be removed and with a flashlight check the springs. Otherwise it will take removal of the gear to inspect.

Now a clunk while shifting can occur in the inline. Especially if the shaft is free wheeling due to movement of the boat or current in the opposite direction of the shift.
Most of the time that is the noise of the plate springs taking the brunt of the shift torque.

The construction of a typical gas engine drive plate is the large outer plate is bolted to the flywheel.
In the center is a smaller seperate plate with the drive spline for the gear input shaft.

Around the outside of the smaller plate are heavy springs that hold the smaller plate firm and compress to take up the rotational shock of shift torque.
As the springs wear, they compress, break and wear the surrounding metal adding to increased hard shifts and noise.

Anytime a gear is rebuilt, the plate should be replaced.
It should be inspected every 1000 hours for wear.

But it is one of the most ignored items on a marine engine.

[Bulletproof]

Hey if you decide you need to swap them out I've got two rebuilt 1.52 velvet drives ready to to. I had them rebuilt before I decided to buy new engines. They skidded and ready to go.

Call me, 781-696-5439