Velvet Drive leakage

[roberttigar]

Trying to solve a leak from the rear seal.
An annoying loss of 2-3 oz over 12 hrs run time-I added "Blue Devil" Trans sealer.
Initially it helped. Checked the boat today and find better than a qt of trans fluid in the bilge and the fluild level way down-doesnt even show on the dip stick.
It not only didnt solve the problem, it made it worse.
The loss was while the engine was off-at the dock.
1-any ideas why the stuff had the opposite affect on the seal.
2-anyone ever replaced the seal on a velvet drive-the one at the outbound end of the reduction gear-how?

Bob

[NoTies]

A common cause of leakage on these transmissions is the O ring between the output shaft and the flange. If the flange retaining nut is loose this will leak. Easier to repair than the lip seal.

[roberttigar]

That's great Pete. But I'm looking at the skematic of the transmission and I dont see an o-ring. Just the nut, coupling and then the oil seal. What am I missing?
Also, do you know the size of the hex nut?
Thanks, Bob

[NoTies]

OK, getting confused in my old age. I now think the Velvet Drive uses Loctite sealant on the splines on the output shaft instead of an O ring. Same end result if loose. Anyone care to confirm?

[shakey doug]

Lip seal only, socket size 1.11/16''. Check seal running area for any marking, may require sleeving or metal spray.

[NoTies]

What seals the splines on the output?

[shakey doug]

My reply should have been presented clearer. Early 70 series splines require a non hardening sealant, later units came dry from the factory. The same sealant should also be used on the seal to casing surface.

[coopec43]

You're not Robinson Crusoe


www.shamrockboatownersclub.com › Forums › Main Forums › Mechanic's CornerTransmission fluid leak | Shamrock Boat Owners' Club


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www.cruisersforum.com › ... › Engines and Propulsion Systems
Velvet Drive Transmission Leak? - Cruisers & Sailing Forums

http://www.cruisersforum.com/forums/...eak-31583.html
Oct 6, 2009 - 4 posts - ‎3 authors
I have just serviced my transmission (replaced seals and gaskets) and re-installed in ... Velvet drives have a history of front seals leaking due to ...

[meridian28]

Mine was leaking at the coupling, the nut had backed off slightly. These are one time use nuts. Prior to installing the nut, fill the cavity with RTV sealant then torque the nut to 200 lbs. Use an impact wrench if possible. The sealant will seal the shaft splines.

[Robert Laws]

I know this is an old thread, but it is very useful, so I want to add a little more information. I have a velvet drive in my narrowboat in Cambridge (UK).

if the breather becomes blocked then the VV is then 'sealed'. As it heats up this means that fluid can be forced out past the lip seals. I found this was happening sometimes. The symptom was loss of fluid and also and that each time I released the dipstick it would 'pop' out like a Champaign cork!

This is easy to solve of course: service or replace the breather. There's no need to remove the transmission.

In the process of looking into this, I took my breather apart. I found that it has only 4 parts: the body, the cap, a spring and a little rubbery 'pad' that presses down on the top the body. It is a one way valve: it allows air out, but not in.

[PNM]

For future searcherss!!!

There is an excellent youtube on replacing the BW VD Seal at:

https://www.youtube.com/watch?v=08XTgrM7QMw

The only thing missing is suggestions about how to do it with the boat in the water

[team karst]

Originally Posted by roberttigar

Trying to solve a leak from the rear seal.
An annoying loss of 2-3 oz over 12 hrs run time-I added "Blue Devil" Trans sealer.
Initially it helped. Checked the boat today and find better than a qt of trans fluid in the bilge and the fluild level way down-doesnt even show on the dip stick.
It not only didnt solve the problem, it made it worse.
The loss was while the engine was off-at the dock.
1-any ideas why the stuff had the opposite affect on the seal.
2-anyone ever replaced the seal on a velvet drive-the one at the outbound end of the reduction gear-how?

Bob

I have done this job, but different boat. The amount of working clearance behind the flange makes a huge difference in effort. Engine gets to stay, or it gets to move forward...
First, make positively certain the leak is not from any oil cooler lines.
Second, early VD's have bolts to the rear of the planetary housing, making this job easier.
Third, use an impact wrench on the big nut, off and on.

[PNM]

I just have a little drip that stops if the ATF is barely above the minimum acceptable level.

I want to replace the seal with the boat in the water, but, I painted the prop shaft with "the best" two part metal underwater paint and am worried I cannot slide the prop shaft back 6" because the paint will conflict with the prop shaft bearing underwater near the prop.

I might be able to get a diver to scrape the paint off the shaft in front of the bearing while they are doing my annual in water bottom cleanup.

I have two concerns one of our member experts may be able to help me with.
1) am I correct that paint on the prop shaft, underwater, will make it impossible to slide the shaft aft 6"?
2) how do I keep "too much" water from running into the boat when I slide the shaft 6" aft through the dripless through hull box? The shaft would still be in the stuffing box.

Any thoughts will be appreciated. It will cost me $1000 to have the yacht pulled, blocked, and relaunched - to replace $30 of parts

[roberttigar]

Before you do all that work, make sure the drip is not the result of a bad o ring on the gear shifting shaft.
Bob

[Rumrace]

Hypoid oil is notorious for absorbing water. When it heats up it finds a leak because it does not have adequate area to expand.
Could this be possible