JCB 801 slew problem

[cartonj]

Hi I just registered and am looking for help with my old JCB 801, its 91 or 92 I believe.

The issue is that the slew is quite slow especially to the left, everything else works fine. Oddly if I raise the blade and hold the lever the slew works perfectly in both directions.

Any advice would be greatly appreciated.

[ianoz]

Sounds like Centre joint Problems .in need of new seals , But Muz and Mick the fitter ,are far more qualified to answer .

[cartonj]

Thanks ianoz. I forgot to say its non servo.

[ianoz]

UMMMMM , Thinking about it ,No Not the Centre joint . ,As the slew motor should be up top .

[Mick-the-fitter]

UMMMMM , Thinking about it ,No Not the Centre joint . ,As the slew motor should be up top .

I agree, slew motor above the distributor, the connection would lay within (1) the valve block, spool movement may be! (2) the motor is fitted with brake valves these can leak, when you hold the blade lever up and slew fully right or left and then let go of the lever, does the machine stop in equal distance both ways?

There are some tests we can do by changing hoses and valves!

Mick

[cartonj]

The slew does stop equally both ways when I let go of the levers, if I let go of the blade lever but keep hold of the slew it goes back to a crawl each way.

I must check the lever movement as nothing happens at all until the lever is pushed to the maximum.

Why the blade lever boost the speed?

[Mick-the-fitter]

The slew does stop equally both ways when I let go of the levers, if I let go of the blade lever but keep hold of the slew it goes back to a crawl each way.

I must check the lever movement as nothing happens at all until the lever is pushed to the maximum.

Why the blade lever boost the speed?

When the blade reaches the end of its stroke, it reaches its relief pressure and returns oil to the tank via the relief valve, this would be set at a high pressure, therefore the spools between the blade slice and the relief valve we be fed high pressure oil from the return side, this may block any slew system leaks.

therefore the slew operation seems to work properly! Your fault may lay then with the travel on the spool for slew on the side that doesn't move very fast, remove all the cover to access the control linkages and spool block, without the engine running just move the slew lever fully both ways and see what happens! When you have found the spool for the slew, also you can try afterwards changing round the two hoses, and see if the fault swaps sides.

Mick

[Muz]

First for me would be to check the pump ... I assume it will be a triple section gear pump on that machine, one bank commonly fails, you need to do a pressure test to keep things simple first of all.

When you hold the blade to relief pressure, the slew will gain through the block, from another pump section, as JCB block architecture isnt the best

[cartonj]

Thanks for the advice guys, I'll have a look at the linkage and pump pressure and let you know.

[cartonj]

To follow up, I took a look today and decided to adjust the travel stops on the lever to see what happened. As luck would have it I now have a good slew in both directions, so seems a simple fix. The one issue I have is that the lever doesn't return to neutral, its always been stiff and I fitted a couple of springs previously to pull the lever to centre but it might need a couple of stronger springs.

[Muz]

To follow up, I took a look today and decided to adjust the travel stops on the lever to see what happened. As luck would have it I now have a good slew in both directions, so seems a simple fix. The one issue I have is that the lever doesn't return to neutral, its always been stiff and I fitted a couple of springs previously to pull the lever to centre but it might need a couple of stronger springs.

So you mean the pilots were the problem ? or the dozer lever detent ?

[cartonj]

Valves mustn't have been opening enough with the lever travel, the linkages are probably worn or someone was messing with the stops (two bolts) previously.

[cartonj]

Separately does anyone know how to grease the slew ring bearing and the ring itself on the old 801. There are grease points on both sides of the body of the machine but whatever lines connected them to the slew ring are long gone.

Cheers

[Mick-the-fitter]

Separately does anyone know how to grease the slew ring bearing and the ring itself on the old 801. There are grease points on both sides of the body of the machine but whatever lines connected them to the slew ring are long gone.

Cheers

Hi mate, I think on that model the slew ring has a drilling on the outside ring which has a grub screw in it, and you can remove it and fit a grease nipple, as for the spool travel and the sticky levers, just buy some WD 40 and soak anything you see that move when you operate the lever each way.

good job

Mick

[cartonj]

Thanks Mick, I'll have a root around and see if I can find a grub screw.