The Classic Machinery Network

Hello all,
I have just bought a JCB 3C mk3 Powertrain. At the moment it will reverse but doesn't go forward. People have mentioned the forward clutch pack will need replacing, but others have mentioned changing the oil in the torque converter will sometimes solve the problem.

Could anyone let me know their opinions on what is causing the fault?

The machine number is: 138059/5

The manual states it needs "Mobil Delvac 1310" in the torque converter. Does anyone know what is a alternative for this fluid?
Also it states the gearbox needs "JCB Super X Universal 20W20". Will any 20W20 oil do, or does it need the special stuff at a special price JCB supplies?
Finally could I ask if anyone knows the alternatives for the axle and brakes? Again the manual states "Super X Universal 20W20" for the axle and "Mobil Hydraulic Brake Fluid 550" for the brakes.

Thanks in advance, Gary.

If you look up the spec of the Mobil equivalent for the 20W20 it appears to be a universal engine oil. Remembering back for the Torq Con I used JCB special torque (or somthing sounding like that) which was an SAE 10w light engine oil , an 80w90EP for the gearbox (must be suitable for syncros) and JCB special gear oil in the back axle with wet brakes. In theory any transmission oil designed for oil immersed brakes should do but I found some squawked badly. I guess the JCB oil had better additive package? The brake fluid was, IIRR, just hydraulic oil and not automotive brake fluid.

Hello Pete, thanks for the reply and your advise.

Where in Essex are you from? I noticed in one of your other posts you use Euro Lube, so I'm guessing your around the Southend area like myself?

Yes Benfleet. Give Gary Evans a ring at Eurolube and he will sort out oils you need and ought to be competitive.

your drive problem could be clutch plates worn out , low oil , or out of adjustment dump spool .

Very close then Pete, I'm only in Hockey. Do you have many machines yourself?

Yes I have met Gary a few times and go there for fluids.

Phil, how do you adjust the dump spool? These powertrains are new to me, only played around with the common manual box on other 3c's

I don't have a wheeled digger any more Gary. I have just dropped in with the name!

the dump spool is in the middle of the forward/reverse selector ,it is spring loaded pushing out , you should be able to push it back in about 25thou anymore than that it is loosing drive and it's always forward it looses first, it is a smaller piston to operate forward so it needs more pressure, the same as if the box is low on oil ,reverse takes a lot more to destroy .

Fair enough Pete. At least you have the knowledge still.
I drained and re-filled the T/C oil today and then did it again to get more new oil in the system. I also changed the filter.... I still have no forward or reverse though.

Time to take the little sump off and check the strainer!

Phil you mentioned I should be able to push the dump spool in "25thou", what do you mean by this as I guess you didn't mean 25 thousands inch?

I would have thought that clutch pack wear would have give you sluggish symptoms for a while first and as Phil said the forward pack likely to fail first. Probably still best to go down the pressure test route. Do you know Tim Adcock? Could the dump spool have stuck? Do you get any movement with back wheels jacked off the ground?