Velvet drive spins shaft in neutral

[Luchog]

Why would a velvet drive (1:1 71C) turn the shaft so that the boat moves at neutral?
It seemed to turn more when the engine/tranny were cold. and then less after a quick ride.
Otherwise, the transmission performed smooth and silent.

What kind of repair should I look up to??

[Frosty]

Disconnect the cable and make sure the actuating lever absalute central, and that it gets full movement for and aft. Then check the oil --not only for capacity but for the right stuff.

It might turn the shaft --a bit but not enough to move the boat.

[virgo]

I have the same problem. I have checked that the selector is in neutral and I can stop the shaft rotating by grabbing the shaft with my hand and applying a fair ammount of pressure.

The rotation is enough to propell the boat forward which is a pain when you are by yourself and are trying to tie up in a marina.

I have recently replaced the stern glands which were leaking badly and I thought the new packing would cause enough friction to stop the shaft from rotating but the problem is still there.

The oil level is ok and the oil is in excellent condition

Seeking some advice as what to do

[Syed]

Chances are that there is no problem with the drives. Transmission oil is pretty thick and gets thicker at low temperatures and drags the parts along, as we experience with our cars that starting is easier with clutch pedal pressed (in winter). There may be some guidlines from the manufacturer of these drives to use different oils in winter and summer.

[marshmat]

You mean your car will crank over with the clutch pedal out? That's weird, I've never seen a car that will do that, ever.
As to the Velvet Drive, since you seem to have checked the shift linkage and the oil, I see two options. Live with it until it breaks, or tear it down and figure out what is going wrong- possibly the shift mechanism is binding on the driveshafts slightly, so even when the gears are disengaged there is still some torque transfer. Sorry I don't have any better ideas.

[TerryKing]

Originally Posted by marshmat

You mean your car will crank over with the clutch pedal out? That's weird, I've never seen a car that will do that, ever.

Matt, you must be a whole lot younger than (some) of us...

[Frosty]

You may find that the tranny gets hot when under way, unless you dont use it much?

It needs to be pulled apart,---expect to replace clutches,-- a broken snap ring or two would be contributory to your problem.

Its a an interesting theory to always replace trannies rather than overhaul. Unless your really really know what you are doing. If you have to do it twice, you are already at the cost of a replacment.

If you have experienced overheat you may have blue-ing on shafts and gears.

Thats finished it in my opinion especially if this is an ocean going vessel.

OR use it till it dies,---providing--

If its dragging in reverse thats worse than dragging in forward.

[charmc]

Originally Posted by marshmat

You mean your car will crank over with the clutch pedal out? That's weird, I've never seen a car that will do that, ever.

Marshmat,

Transmission in neutral, car starts easily, whether the clutch is in or out. In winter, clutch in will relieve the load of turning the few parts of the transmission that still rotate in neutral................hmmmmm, except the safety lock out switches mandated by friendly govt regulation since the late 80's or so........... hey, Marshmat, you just gave away the fact that you're a heck of a lot younger than a bunch of us!

[charmc]

Back on topic, I've heard of 2 potential causes:

1. Warped or misaligned clutch plates. Not that common, and this condition should eventually show other symptoms, e.g. slippage or vibration at higher speeds, overheating.

2. Leaking shift selector valve, usually from a bad seal. This is more common, sometimes called "blowby". A small amount of fluid leaks past the valve when in neutral, producing the same effect as forward engagement, but with only a very small amount of force.

Unfortunately, either condition will get worse with time, and either will require a teardown to fix. The good news, if it's a leaky selector valve, is that the progression will take time and should not cause any real problem until the leak gets bad enough to make maneuvering in close quarters difficult. I've heard of boat owners leaving this alone for a year or more, but those cases were stricly recreational boats that didn't get used that often.

[virgo]

Thanks to all that have replied,

I was wondering if the selector valve bypassing as suggested by Charmc could be removed and reconditioned without removing the whole transmission

[dsharp]

The selector valve has rings similar to piston rings but they seldom give problems. The clutch plates are sticking causing the shaft to turn. The clutch pack has alternating metal and friction plates. The gears are not to hard to rebuild if you pay attention to how it comes apart. The plates are ford auto transmission parts. Probably safer to get them from borg warner though. It's a pretty common problem and eventually the clutch pack will stick. It may last a long time like it is, though

[dsharp]

I thought of something else. Inside the clutch pack is a metal disc that is shaped like a clutch diaphram. It unloads the plates when the pressure is off, letting the plates slip. The disc tends to flatten out over time. A new one should come in the rebuild kit. The are also two snap rings in the clutch pack about 5" in diameter. One is about .030 thicker than the other and goes inside the pack to hold the plates in. The thinner one holds the pack together. If you get them in wrong it puts to much pressure on the plates and it won't come out of gear. Don't ask me how I know that.