no forward transmission?

[aablecroft]

Hi Folks, I am up the S*** creek,

Got back to my 1988 3cx 4X4 on start up blew ATF filter oil every ware (white) changed rusted out filter with very large stillsons, (I broke 2 filter removers) (Dumped ATF oil White )changed ATF fluid raised rear wheels on legs to find will go in reverse perfect but not forward, poss fault in indicator type selector switch, anyware else i need to look? Alternator frozen up solid also,belt just loosened for now, Can i swop anything to prove it will run in forward ? is there activators on top of gear box ? Radiator fluid was also low but a jubilee clip also rusted out and split on near side do they have an ATF fluid oil cooler If so ware do i look?
Thanks in advance any help greatfully excepted,

[essexpete]

@agrimax and @Slooby may be able to help. I am sure that era will have a cooler that looks cylindrical in shape. I would guess there will be a forward and reverse solenoids that you could check. Look on the tranmission case for a couple of plastic like cubes sprouting a connector that fit over a metal pole.

[aablecroft]

Thanks for reply yea i saw two square cases about 50mmx50mm on top of box i just wondered if i swopped over these solenoids on tranmission case would reverse on selector switch then become forward to test forward drive. and look for fault between them Its the Grey cab inside colour,would you know where about cooler may be, cheers

[agrimax]

Use a multimeter(a test bulb of at least 21w would be better) to check if there's power at the solenoids when the f/r lever is activated both ways. Just to make sure they are both actually getting power to start with. There are relays behind the dash (left hand side iirc)that you should hear click with the just key turned on. When you know that power is going to the solenoids,you could swap them over and see what happens...
White oil in the transmission is not good news as the water will destroy the linings on the clutch pack plates. Wonder if it will still reverse when loaded ie,on the ground?
The transmission oil cooler should be a long cylinder either below the radiator or between the engine and radiator in front of the crank pulley. (Early models had a second radiator in front of the coolant radiator)

[aablecroft]

Thanks for the reply that helps a lot that would prove wiring/switches all the way to solenoids, best i can hope for is forward solenoid is getting no power then trace back to find why not. if both are powered it could be solenoid fault. Friend gave me his old F/R lever he had the same fault one his machine, no forward drive they fixed his with new f/r lever, I dismantled and checked his old one with mutimeter and forward micro switch was faulty.!
When in reverse mine was strong off the ground (impressive) and i had to take it out of front drive 4x4 as it was trying to push whole JCB back with front wheels on ground but with bucket and back arm down so maybe a bit of hope plates are ok

Do you know if the same Clutch pack plates drive forward and reverse drive ? seems likly to me but i am no expert by any means
I will look for Oil cooler, I take it I could bypass this as a temp measure? it will be a couple of weeks before I can get back to it as its on a Island that i am not. I will let you know how I get on Thanks again

[agrimax]

Yes you could bypass the cooler temporarily. The clutch pack housing or basket is a double sided component with a set of friction and steel intermediate discs on each side of it. A set for forward and a set for reverse...

[aablecroft]

So the problem could still be the forward clutch pack ?

[agrimax]

Could be. There's also a gasket between the pressure maintenance valve and transmission housing that may be leaking past on the forward circuit. The PM valve is what the f/r solenoids are bolted onto.
If you go into the downloads section of the forum,you'll find a workshop manual that covers your transmission and how to pressure test it.
Go to downloads,
Earthmoving equipment,
JCB, and then to the second page,at the bottom of the list,

JCB 3CX/4CX Backhoe Loader workshop manual SN 290000 - 400000.
Chapter 6 page 18-1 for pressure testing and page 16-1 and onwards for that transmission overall.

[aablecroft]

Thanks again hope to be back there next week end i will let you know how i get on