Rear lift not working

[forrest carver]

This morning I attached a york rake to my L275DT. Once connected, I pulled the lever to lift the attachment to the top of the stroke, which worked fine. When I pushed the lever to drop it back down, it seemed like something "gave out" and the attachment went down very quickly. I was not able to lift it again. The lever still moves through its normal range but does not operate the rear lift. I didn't see any fluid leaking anywhere.

Any ideas?

For what it's worth, the lift was evidently working as it should a few years ago.

 

[GreensvilleJay]

Maybe the seals in the ram have worn out ?

'worked a few years ago' suggests it's NOT been used for years,which could mean the seals have 'dried out' or gotten hard.
Also it's possible that rain water, over the years has gotten into the cylinder,rust forms, stuff fails...

 

[Edke6bnl]

on my b7800 and some others there is a control for the drop speed under the seat and rotating knob. I believe its main purpose is to prevent the 3 pt from dropping during transporting on roads.

 

[forrest carver]

Yes, both of those problems seem possible. The tractor has almost never lived undercover in its entire lifetime, and it's only been used for a few hours over the past decade.

How might I check these seals?

I attached a snip of the workshop manual's section on troubleshooting a nonfunctional lift. Diagnosis of those issues, however, is beyond my ken.

What are they referring to with the "spool"? What is the difference between the "draft control lever" and "position control lever?" Edke6bnl are you referring to the draft control lever?

 

[GreensvilleJay]

'spool' should mean the actual valve that controls the oil going to /fro the cylinder
'draft control' allows for an implement to be automatically adjusted to maintain a certain height,relative to a fixed point in space(has dynamic response based on feedback)
'position control' puts the implement at 1 position, if tractor goes up, implement goes up too,implement is 'fixed height ' from tractor(no feedback)

 

[forrest carver]

OK, I don't think my tractor has a draft control.

I noticed that when I manipulate the position control lever, the other side of the assembly does not move (I drew a blue arrow pointing to the area that I would expect to move, but does not, when the lever is moved.)

Is access to the spool and spool drive lever easy? It looks like I'd need to crack a big case...kind of intimidating

 

[TheOldHokie]

'spool' should mean the actual valve that controls the oil going to /fro the cylinder
'draft control' allows for an implement to be automatically adjusted to maintain a certain height,relative to a fixed point in space(has dynamic response based on feedback)
'position control' puts the implement at 1 position, if tractor goes up, implement goes up too,implement is 'fixed height ' from tractor(no feedback)

Common misconception. Draft control does NOT maintain a fixed height. That is what position control does.

Draft control is the opposite. Draft control is used to maintain a fixed 3pt pull (draft) from the implement. This is useful for maintaining traction when pulling ground engaging implements like moldboard plows. When a ground engaging implement (plow) hits hard soil conditions and pull at the 3pt (draft) increases the implement is raised and runs shallower. When implement enters softer soil and pull at the 3pt (draft) lessens implement is lowered and runs deeper.

Dan

 

[forrest carver]

I removed the attachment and tested the lift. Lo and behold, it actually does work. The issue is power....it can barely lift 50 pounds.

 

[TheOldHokie]

I removed the attachment and tested the lift. Lo and behold, it actually does work. The issue is power....it can barely lift 50 pounds.

I removed the attachment and tested the lift. Lo and behold, it actually does work. The issue is power....it can barely lift 50 pounds.

Sounds like a hydraulic pressure leak somewhere. Given the abrupt nature of the failure I would be inclined to suspect a 3pt pressure relief valve. Can't seem to find any in the parts diagrams.

Do you have a loader on the tractor?

Dan

 

[forrest carver]

Yes, it does have a loader

The loader was working great until one of the hoses sprang a major leak today. So I'll need to replace at least that hose in addition to figuring out the rear lift issue.

The drop speed knob still functions as it should in the rear lift.

Here's the troubleshooting guide for a "slow lift" (which is true, but a better root would be "weak lift"):

The relief valve assembly is #17 below.

Since you both mention relief valve, that's where I'll start. I'm guessing it's that bolt on the right, perpendicular to the two mounting bolts? Am I good to tighten/loosen that and check for an effect?

Here's relevant info from a service manual for a similar tractor. It looks like they want you to add/remove shims:

 

[TheOldHokie]

Yes, it does have a loader

The loader was working great until one of the hoses sprang a major leak today. So I'll need to replace at least that hose in addition to figuring out the rear lift issue.

The drop speed knob still functions as it should in the rear lift.

Here's the troubleshooting guide for a "slow lift" (which is true, but a better root would be "weak lift"):
View attachment 87129
The relief valve assembly is #17 below.
View attachment 87131

Since you both mention relief valve, that's where I'll start. I'm guessing it's that bolt on the right, perpendicular to the two mounting bolts? Am I good to tighten/loosen that and check for an effect?

Here's relevant info from a service manual for a similar tractor. It looks like they want you to add/remove shims:
View attachment 87134

I am familiar with those diagrams just not sure they are applicable to your machine. Turning the bolt does not adjust anything. Unscrew it and you can remove the poppet and check for debris that may be holdingp the poppet off its seat.

I find it noteworthy that you popped a hose on the loader. That seems awfully coincidental especially since the loader is also the source of pressure for the 3pt.....

Dan

 

[forrest carver]

I was advised to add some hydraulic oil...could I have added too much? Felt like about a pint, maybe it was a quart.

The tilting the bucket up causes a geyser, but all other loader controls function as normal.

 

[forrest carver]

Unscrew it and you can remove the poppet and check for debris that may be holdingp the poppet off its seat.

Does the system need to be drained, or any levers in certain positions, to do this?

 

[TheOldHokie]

I was advised to add some hydraulic oil...could I have added too much? Felt like about a pint, maybe it was a quart.

The tilting the bucket up causes a geyser, but all other loader controls function as normal.

Not your problem.

Dan

 

[TheOldHokie]

Does the system need to be drained, or any levers in certain positions, to do this?

Its just a cap with spring, poppet, and shims inside. Probably not the problem but easy to inspect. Just unscrew the cap and remove the parts making sure you dont lose anything and you know what order to put them back. Check inside for any foreign material and clean if necessary. Reassemble in same order as removed.

Which hose on the loader blew out?

Dan

 

[forrest carver]

Which hose on the loader blew out?

The leak hole is on the rear hose in the pic, obscured by the front hose

I'll check the relief valve tomorrow in daylight

 

[forrest carver]

The rear lift decided to start working properly again today, not sure why. There was some hose interfering with a mechanism on the other side of the lever, maybe that was the cause. In any case, looks like the problem's licked now.

I got the bucket loader hose replaced. NAPA is awfully proud of their hydraulic hose! $45 for that little section.