JCB 3CX moves loses drive

[Timmusdavies]

Hi, I have a JCB 3CX 1986, and when it drives, it very quickly loses momentum and drives really slow. It seems fine when I’m driving into earth pile, it’s just when I start travelling any distance It starts losing drive power. The engine doesn’t slow down though. Anyone have any ideas what this could be?

 

[Mick-the-fitter]

Torque converter issue! Try low ATF oil or wrong oil! Serial number if you have, may be able to give more help.

 

[DaveDCB]

Had similar with a newer version, Transmission fluid was boiling out of the dip stick… I don’t imagine you’d be travelling the kinda distances in your 1986 vintage tho?

 

[V8Druid]

Torque converter issue! Try low ATF oil or wrong oil! Serial number if you have, may be able to give more help.

my '87 black cab sitemaster had dexron free ATF in the TC

 

[Timmusdavies]

Torque converter issue! Try low ATF oil or wrong oil! Serial number if you have, may be able to give more help.

Thanks. Serial Number is - 3CX-4/320097/P/S

 

[V8Druid]

Hi, I have a JCB 3CX 1986, and when it drives, it very quickly loses momentum and drives really slow. It seems fine when I’m driving into earth pile, it’s just when I start travelling any distance It starts losing drive power. The engine doesn’t slow down though. Anyone have any ideas what this could be?

brakes binding on ... does it roll freely??

 

[Mick-the-fitter]

The drive pump also can give an issue if low on oil, or when cold the oil is thicker!

 

[Mick-the-fitter]

I know you can’t get any speed in reverse if it’s possible to, would it do the same?

 

[Bri963]

Really need a bit more to go on. How many hours on the oil/filter, is the level good, what oil is in there, is the trans cooler blocked, does it happen in all gears? Is it throwing a high trans temp. warning? There really isn’t much more. If the transmission was getting worn it would be playing up in some gears and not others, and in the same gear forward or reverse. Have you had the cooler off and cleaned the airways and flushed the oil passages? Don’t think they had the locking torque converter at that age, and no sensors to cause issues other than trans temp. Mick is more of the guru on these machines.

 

[Canal Navvy]

At that age would it be the torque converter, reverser, four speed manual box with a dump pedal to change gear ?

 

[Bri963]

Even simpler, then. Mind you, I have a feeling that the power shift machines were out by then. Mick?

 

[craig]

1986 that would be a black cab? power shifts didn`t come until early 90`s I think.
A black cab has an electric foward/reverse shuttle, one of the coils could be breaking down, opening the valve but struggling to hold it open, try swopping the coils over to see if it move the problem.

 

[Mick-the-fitter]

As has been said, 4 speed box, and shuttle on forward and reverse, but if the forward shuttle clutch pack is worn, which in some cases we replaced only the forward pack, normally after it being used to load in 3rd or 4th! Therefore the issue would happen in reverse.

Using jack legs and front loader lift all the wheels off the ground and drive backwards, see if you get the same problem in reverse? I would still comeback to the oil and it’s system.

 

[Timmusdavies]

Great, thanks for your help everyone. There was one time where one back wheel seemed to have be stuck on, but that seemed to have sorted itself. If I jack it up, all wheels run freely, and when it's cold the drive seems to work better, so I think it must be transmission oil needing topping up. Does anyone know what transmission fluid I should use?

 

[V8Druid]

Great, thanks for your help everyone. There was one time where one back wheel seemed to have be stuck on, but that seemed to have sorted itself. If I jack it up, all wheels run freely, and when it's cold the drive seems to work better, so I think it must be transmission oil needing topping up. Does anyone know what transmission fluid I should use?

could well still be brakes binding up when hot .... has it stood for any length of time?

When I loaded JakieB out, up the drive, when he went, mine were starting to bind - big time ... everything'd warmed up after several hundred yards of pull up the hill ... reckon if I'd slacked the bleeds off it'd have helped



climbed onto Simon's truck sweet as though, first go, no grief or dramas

 

[Timmusdavies]

Just jacked it up and did notice that one of the back wheels wont turn very well when in drive, so it must be brake binding! How do I free it?

 

[V8Druid]

Just jacked it up and did notice that one of the back wheels wont turn very well when in drive, so it must be brake binding! How do I free it?

could try opening the bleed to start ... might have pressuried once hot/warm ... doubt it'll be that easy though ... mine were fine cold, but'd soon warmed up on the climb out of here ....... dare say it'll have become stiff (seized) sat about

 

[Bri963]

Do it again then go under and feel the brakes. If one is binding it’ll soon heat up.

 

[craig]

I seem to recall there was a change in the way the transmission oil was checked in the black cabs, ticking over with oil hot, vs within 30 sec of stopping engine?
I`ve got a white cab and black cab handbooks here somewhere

 

[V8Druid]

I seem to recall there was a change in the way the transmission oil was checked in the black cabs, ticking over with oil hot, vs within 30 sec of stopping engine?
I`ve got a white cab and black cab handbooks here somewhere

seem to recall that being correct Craig