Ferret Gearbox Lubrication

[MiketheBike]

I know this has been covered many times, and there seems to be conflicting advice, so would appreciate some real world lub advice.

 

What should I be using in a ferret gearbox?

My initial thought is to use SAE30 (I have a Unity motors up the road that does all the mono-grade oils, so no problem sourcing), or do I use multi-grade.

 

I took the filler off the gearbox, and its low on oild, but more worrying there is quite a bit of oil that appears to have turned to a thick grease (caused by mixing oils?).

How do I get rid of the deposits before refilling the gearbox (remove the gearbox top plate?).

 

Thanks

 

Mick

ps...I feel like a scrounger at the moment...continually coming on here asking for advice!!!!

[sirhc]

Mick,

You will need to put SAE30 in the gearbox, and EP90 in the transfer box. If I remember correctly Richard F mentioned that a few ferrets took the same oil in both, but I'm fairly sure yours will be the same as mine. You could try flusing out the gearbox, I'm not sure what kind of cleaner would be suitable though. If I were you I'd drain it, fill it with fresh oil, run it for a few miles and then change the oil again. Hopefully that will get rid of any nasty old oil.

 

Chris

[MiketheBike]

Thanks Chris,

 

yes, from what I can make out its EP90 in the transfer box, but I want to drain all the fluids over the next couple of weeks so I know where I'm starting from.

 

Just wanted to confirm the SAE30 thing, as there are articles that say use multigrade, others that say only use SAE30.....maybe its easiest/safest to stick with original spec. Just wanted to see if anyone had any real strong views on either.

 

Cheers

 

Mick

[sirhc]

Mick,

I've been using SAE30 in mine for years with no problems. If yours is anything like mine you'll get through loads of EP90!

 

Chris

[Richard Notton]

Mick,

You will need to put SAE30 in the gearbox, and EP90 in the transfer box.

Maybe a bit of background might help.

 

SAE oil ratings only refer to viscosity, other codes tell you what it actually can do.

 

Most misunderstood is the fact that the SAE viscosity ratings _overlap_ and it is essential to realise that "crankcase oil" and "gear oil" have different scales. In fact SAE30 engine oil has the same viscosity as SAE80 gear oil; there are so many scales that the industry now uses centi-Stokes (cSt) as you'll find when speaking to any oil lab tech.

 

It seems common that 50s/60s British mil stuff uses SAE30 engine lube in gearboxes, it could be for commonality and field servicing or because of phosphor bronze bearings that are eroded by the EP or Hypoid additives that gear oils are laced with and give them that recognisable, acrid, cat's P smell. :-)

 

Multigrade oils are loaded with plastic magic; long chain polymers, to hold the viscosity with temperature. All the major makers labs I spoke with seriously warned against multigrades in gearboxes as the plastic will not survive the mechanical forces and will be rapidly reduced to their base stock - a 15W/40 will become just SAE15 quite quickly.

 

It is likely an EP oil in a Ferret or similar Wilson pre-selector box will allow the brake bands to slip too; some automotve makers do rate some mil qualified SAE30 engine oils as a transmission fluid, Caterpillar and Allison to name two.

 

Its not so old hat as you might think, industrial plant from small to gigantic uses 30 in many applications and a detailed read in many current car handbooks and howling Jap m/cycles shows SAE30 quite acceptable in temperate applications. If you ever come across a Detroit Diesel Allison V53 or V71 engine then only SAE30 is acceptable.

 

The original specs you are interested in would be MIL-O-2104B which is called up under OMD110, this is available as Total Rubia B30 but I do not know if it is supplied in less than 205L drums; fortunately between me and some friends we can use it in a year and a half in these quantities, delivered free too from Total-Butler. (Reminds me I must order some tomorrow!)

 

I have known people with Ferret gearbox troubles entirely due to SAE90EP being inadvertently used. They have found red diesel to be a good and cheap flushing oil (diesel _is_ very thin oil) by running at idle for a few minutes and then allowing a protracted period to drain. Replacement with SAE30 had the box behaving as normal.

 

Your mileage may vary of course. ;-)