The Classic Machinery Network

Just bought a jcb 3c mk 2 to use doi g light work and to restore. All looked to be good, everything works. However, when i dipped the gearbox with a brazing rod, as no oil was sgowing up in dipstick, the rod came up completely dry.

Clearly the oil has gone somewhere. Is there a particular seal that leaks catostrophically and dumps the gearbox oil? Can this seal/gasket be replaced without taking the gearbox out?

The gearbox still seems to work well so was thinking of just taking out the drain plug and draining anything in there and then refill with new oil.

When the gearbox eventually does pack up, can the gearbox be rebuilt without removal from the machine? (I am fairly certain of the answer to this is no but thought i would ask anyway in case someone has managed to do it).

Are gearbox parts expensive and is it better to get a good second hand gearbox?

What oil to put in rear axel/ differential?

My plan is to give the machine a full service and then start restoring bit by bit. Engine and hydraulics seem good.

Any advice much appreciated.

Sean

I take it this is a manual gearbox with a clutch?

Yes manual 10 speed

Gearbox and back axle share the same oil. Any universal 10w30 or 15w30 will do. Even a gear oil throughout will work as the brakes are dry and separate. You'll maybe see a leak when you refill but the gaskets between the trumpet housings and centre housing may be leaking or the half shaft seals out at the wheels are prone to going.Maybe even the front gearbox seal or a combination of them all would empty the box through time.
The gearbox housing is part of the rear axle centre housing and I'd guess the lot would need removed to rebuild the box. They can be noisy anyway but seem to just keep going on.

Thanks. Much appreciate the information. How much oil to fill from dry. Manual for 3c says 50 litres? Also specifies ep90. Did the spec change? I use 15w/30 in the tractor. Is the gearbox from a nuffield/leyland tractor?

Yes Leyland /Nuffield skid. I wonder if the spec is different at the oil is not used for hydraulics unlike the agricultural tractor?

Right enough about the gear oil and the 50l quantity but if universal is good enough for the tractors, it'll be fine in the digger too.Suppose the thicker stuff will take longer to leak out mind you!

Hi,
I always used EP90.
There must be a reason why JCB specify EP90 as opposed to the Universal Tractor Oil specified for the Nuffield tractor. It may not just be the fact that the tractor uses the gear box oil for the hydraulics.
I think that the JCB transmission would be subject to a deal more shock loading than the tractor, especially on front loader work .
There should be tell tale signs of any leak serious enough to empty the box completely, whether from the axle seals or anywhere else.
Did the previous owner drain the oil and not refill it
Perhaps he drained it then forgot, or thought he would save the price of 50l. of oil as the machine was being sold anyway.

Fred

I think Fred is right. Fordson specified a lighter transmission oil for the agricultural Major fitted with internal hydraulic system than say Chaseside or Weatherill.

Thanks guys for the info. I think i will go for the ep 90. The guy i bought it from had no clue mechanically and used ro hire a guy to service it apparently. Looks like slew box is almost dry as well when i dipped it. However there is no wear on king pin or any bushes or other pins. Tyres are also original. It may hust be that it has been sitting for a long time. The brakes have seized. I dont think it has been used hard, just sat around a lot. The bottom of the machine has oil all over it. Took out hydraulic filter now and oil has a lot of water in it. Filter is black. Will drain all hydraulics, clean gauze and replace filter.

Where is the drain plug for the gearbox? Cant seem to see one. Also, how do i drain the slew mechanism, where is the drain plug for that? Is it the big bolt at the bottom?