Oil for Ferret Fluid Coupling?

[LRDG]

At the Oshawa Museum, I found Dexron ATF in the fluid coupling of the Ferret I am working on. I notice significant creep/drag when in gear at a relatively low idle speed of around 400-500 rpm.

ATF has a viscosity grade of around 30 whereas the tables I have seen on various sites recommend a ISO 10-15 viscosity grade oil, based on the OM13 military spec. Seems logical the much more viscous oil we are using is the cause of the creep. What are you Ferret owners using?

EDIT: A second attempt at searching found a site that says, "DO NO USE ATF!" And to drain it, "you need to remove either engine or gearbox". Oh dear. Is there no other option? For example, where does the oil drain when the seal leaks?

[Wayne Henderson]

Drain out the ATF via the filler plug. ATF is too thin.
I used normal hydrolic oil as in hoists, rams etc with no problems.
Wayne.

[Chris Preston]

Check out this link - scroll down to the bottom for the chart with the list of fluids, and a second diagram showing what goes where.

http://www.ferret-fv701.co.uk/useful_info.htm

Hope this helps.

Cheers,

Chris Preston,
Victoria, BC

[LRDG]

Originally Posted by Chris Preston

Check out this link - scroll down to the bottom for the chart with the list of fluids, and a second diagram showing what goes where.

http://www.ferret-fv701.co.uk/useful_info.htm

Hope this helps.

Cheers,

Chris Preston,
Victoria, BC

Chris, That's the link that says I should be using ISO 10 or 15 viscosity grade oil in the fluid coupling, which is a very thin, quite specialized oil for high speed spindle bearings. It's MUCH thinner than the ATF that's in there now, which has 30 grade viscosity.

I did some more searching and the consensus, especially over on HVMF, is that OM-13 spec oil is indeed ISO 10 or 15 viscosity grade.

I suspect the heavier ATF is contributing to the quite high drag I get from the fluid coupling, especially when engaging 1st and 2nd gear at a standstill.

Anybody know how I can drain the fluid coupling without having to split the engine and gearbox?

[Richard Farrant]

Originally Posted by LRDG

Chris, That's the link that says I should be using ISO 10 or 15 viscosity grade oil in the fluid coupling, which is a very thin, quite specialized oil for high speed spindle bearings. It's MUCH thinner than the ATF that's in there now, which has 30 grade viscosity.

I did some more searching and the consensus, especially over on HVMF, is that OM-13 spec oil is indeed ISO 10 or 15 viscosity grade.

I suspect the heavier ATF is contributing to the quite high drag I get from the fluid coupling, especially when engaging 1st and 2nd gear at a standstill.

Anybody know how I can drain the fluid coupling without having to split the engine and gearbox?

You are correct, ISO10 is one of the thinnest hydraulic oils. The common grade for plant machines, cranes, etc. is ISO32, so you can see there is a difference.
I spent many years working on British Army military vehicles (41 actually) and have dealt with fluid flywheels in everything from the 1940 Daimler Dingo to the CVR(W) Fox. The Dingo originally had engine oil in the flywheel but postwar this was changed to OM13 (ISO10), there would have been drag I suspect with the engine oil, but they would not have had anything more suitable in their inventory of oils at the time.
If you really want to drain the oil, it will make one wholly mess, the oil capacity is about 9 pints and that will flood out all through the base of the vehicle before any of it could be drained from the hull. Better to wait until you have to pull the gearbox, then it can be drained in to a container, without too much mess.

[LRDG]

Originally Posted by Richard Farrant

You are correct, ISO10 is one of the thinnest hydraulic oils. The common grade for plant machines, cranes, etc. is ISO32, so you can see there is a difference.
I spent many years working on British Army military vehicles (41 actually) and have dealt with fluid flywheels in everything from the 1940 Daimler Dingo to the CVR(W) Fox. The Dingo originally had engine oil in the flywheel but postwar this was changed to OM13 (ISO10), there would have been drag I suspect with the engine oil, but they would not have had anything more suitable in their inventory of oils at the time.
If you really want to drain the oil, it will make one wholly mess, the oil capacity is about 9 pints and that will flood out all through the base of the vehicle before any of it could be drained from the hull. Better to wait until you have to pull the gearbox, then it can be drained in to a container, without too much mess.

Thanks, Richard. That's a bit disappointing. I really wanted to get some thinner oil in there because right now she almost stalls at idle when first or second gear is engaged from neutral. I've got the idle mixture screws set on the lean side so I'll try setting them a bit richer to see if that helps. The idle is around 400 rpm and I can change forward/reverse quietly at that rpm so I'd like to keep it low.

She runs too cool as well. The new thermostat may improve the idle stability.

We have a spare engine and gearbox so I'll take a look just to see where the fluid coupling oil would drain out of the bell housing and to confirm I can't get a drain trough up through the gearbox drain hatch to direct the oil. The oil could be drained quite slowly by rotating the open fill plug hole gradually downwards.

Also I might be able to suck some oil out with small bore tubing through the fill plug.

[Lynn Eades]

Does the fluid flywheel / torque convertor shares the same oil supply??
Does it also have a trans cooler?
In a car you disconnect a hose from the cooler and the trans pump pumps it out while you top it up with the new oil. I was party to a feret trans (Mr Wilsons brain child) rebuild many years ago (army mechanic recon course), but have forgotten most all of it.

[Richard Farrant]

Originally Posted by Lynn Eades

Does the fluid flywheel / torque convertor shares the same oil supply??
Does it also have a trans cooler?
In a car you disconnect a hose from the cooler and the trans pump pumps it out while you top it up with the new oil. I was party to a feret trans (Mr Wilsons brain child) rebuild many years ago (army mechanic recon course), but have forgotten most all of it.

A Fluid Flywheel and a Torque Convertor are two wholly different drives. The FF is self contained, no pump or cooler.