3-Point lift not right

[Lesfen]

The lift on our '62 Super Dexta has not been right for some time.
It works great with no or a small load on it but when loaded and moving the quadrant lever about 1/5 of the way up it will suddenly raise right to the top and stick there. Putting the quadrant lever to bottom and waiting a few minutes or moving the the lever up and down about 3 times it will slam back to the ground.
Took the cover off, replaced the cam follower pin (which was 1/2 worn through) and readjusted the linkage as per the Wiki (Thank you to Brian!), changed oil, exhaust filter, gaskets and o-rings.
Works more smoothly with no load but still the same with mower on.

Did notice that the bottom rubber flat washer on the filter was not the correct one. This one is larger, thicker with a greater ID and no back up metal washer.
Could there be a lack of back pressure that would cause this problem?

Anyone else had similar troubles?
Did a forum search but nothing exactly the same.
Thanks,
Les

[Brian]

Les,

Are you in Position Control or Draft?

It could be Draft control linkage and the top link are getting pressure from the implement as it raises. Any stabilizer bars going to the top link?

Could also be sticking unload valve. Has it got an "O" ring on it or is it the one with a metal piston ring? If you throw the "O" ring away it will work better. (Genuine Ford answer in the day when we were replacing sheared studs in the unload valve retaining plate).

The exhaust line needs to have around 12 psi in it for the unload valve to work. If the oil is leaking past your "wrong" washer and the valve at the base of the pipe is not able to hold the pressure due to leaks, it could be the answer to your problem.

[Lesfen]

Thanks for the quick reply Brian,

In Position Control but also tried it in Draft for a few moments.
No stabilizer bars to top link but one to left side.

I'm sure that oil must be leaking past the bottom washer on the filter so no 12psi!
Off comes the top again!
Thanks again,
Les

[Lesfen]

Update.
Sealing washers for the exhaust filter arrived so..
1)Took off top, replaced them.
2)Removed oring from the unloading valve.

Now.
Quadrant lever moves about half way up before it lifts right to top and have to put it down to bottom before it will let loose and bang to bottom with an implement on it.

Also noticed when changing the follwer pin and reajusting settings I also removed auxillary control valve to change o-rings and gasket that...

The flow control works backwards!!! (and still does after this latest go round.)
Pulling the quadrant lever all the way to the top also slows the flow to be almost nonexistent.

The parts manual calls for 5 of 1 size o-ring under the auxillary cover but I can only find 4 spots for them? (so 7 o-rings in total not the 8 in the parts book)

Advice please!
Thanks,
Les

[Brian]

Les,
Could you post a picture of your ram cylinder please.



Your plate should be like the one on the right, there are 4, 1,1 and 1 "O" rings which make seven in my book.



I cannot understand how the flow control can be reversed unless it is assembled incorrectly. Has it been to pieces?

I wondered if the ram cylinder has been changed for a 3000 one. That can give problems in setting.

[Lesfen]

Brian,
Thanks for the reply.
It will be atleast a week before I can pull to cover off again to take a photo.
And I'll check my settings again.
S. Dexta has to go to work as is, as we have a great crop of thistles here to mow this year!

Have not have the aux control apart ever, just changed o-rings and gasket when I had to top off to change follower pin a couple of weeks ago.
And.. that's when I noticed that the flow control works in reverse!!
I may swap it with another if I get the chance just to test it.

The lift works wonderfully until a load is put on it!

My aux control does look like the one on the right, thanks for the photo.

Les

[Lesfen]

Hi,
Cleaned up a spare aux control and changed it over.
Lift now works great!
Have not taken the aux control apart so don't know what was stuck or causing the problem!
Expected to find an o-ring had been out of place to cause the speed control to work in reverse but no.

A bit hard to locate the smaller sized o-rings over here that fit under the control.
What's with measurements down to a 64th?
Seems to be lots of room to mill a bit larger space for a more common size of o-ring?

Checked the thickness of the oiled gasket I got from NH that fits under the aux control with a micrometer to be .009".

Put the sickle mower on the '61 Petrol Dexta and having the same lifting problem with it!!
Les

[Lesfen]

Well, lift worked well for a bit and then when moving quadrant part way up started bouncing like it had the hiccups.
And when moving the quadrant a bit higher the arms would lift all the way up again!

Then, worked for 4 hours in 30C weather and it started working perfectly, even better and more accurately than before!!
Must have been a stuck valve of some sort?
Had put in fresh THG oil, which we use in all the tractors so we are not mixing grades and types when hooking on different implements with remote cylinders.
Had read a post somewhere that the new transmission, hydraulic, gear oils do not work well in the elderly tractors??
Opinions or experience from anyone?
Les

[Brian]

I think you have made a slight error Les . Dextas do not use hydraulic oil or gear oil in the gearbox, hydraulics or rear axle, they use bog standard engine oil, 20/30W or 20W or 30W in all.

The problem with synthetic and semi synthetic engine oils is that they attack the rubber seals in the older machines. I do not know, if you replaced every seal in the tractor, whether the new seals would be OK with the new oils.

My oil supplier does not recommend synthetic or semi synthetic oil in any older vehicle. He knows more about the make up of the oils than I do so I can only go by what he says.

I am going to get oil from Morris of Shrewsbury for all my tractors as they do a complete range of oils for the older vehicle to the original oil specifications. That means no extra additives for brakes etc. We will see how I get on.