8n with Sherman Backhoe, Hydraulics fade after warmup

[Midwayman]

I have '52 8n with a wagner loader and Sherman power digger.

My main problem is with the backhoe getting really "weak" after the hydraulic fluid warms up.

In the first 10-15 minutes, I can dig, I can move the machine with the hoe, all is good. But after, say 30-45 minutes, it almost like I lose 30% of my power.

I expect the first question will be if I have a gauge on the pump output. I am waiting for one to arrive. I am not particularly well versed in old hydraulics, so I was curious if this was a pretty tell-tale sign of some kind of issue.

While on the subject, any ideas what kind of hydraulic fluid to use in a unit like this? How about the front loader?

I can only imagine the last time the hydraulic fluid was changed.

Thanks!

 

[504]

Youll know more when you get the gauge on it. Bad
pump,bad suction hose, bad relief valve. On that
hydraulic only system I would use straight 10weight
motor oil or the cheapest hydraulic oil I could find. No
gears to protect just a pump.

 

[Midwayman]

Alright, my gauge came in!

I did some digging and the machine warmed up and started getting sluggish. I shut down and installed the gauge right on the main pressure line from the pump.

At all throttle positions and no levers moved, I see 0PSI.

At 75% throttle, when I pull the stick or the boom against the earth, I generate right around 900psi.

At about 50%, maybe 700psi.

Engine at 100%, I see 1000psi.

This pressure is the same for any of the levers depressed.

From my limited knowledge, that pressure should be closer to 2000psi, should it not?

Is it a safe assumption that the pump is just weak? What are the options for an old Sherman pump. Can these be rebuilt? Are replacements available?

Thanks,

 

[TheOldHokie]

(quoted from post at 16:20:59 05/12/23) Alright, my gauge came in!

I did some digging and the machine warmed up and started getting sluggish. I shut down and installed the gauge right on the main pressure line from the pump.

At all throttle positions and no levers moved, I see 0PSI.

At 75% throttle, when I pull the stick or the boom against the earth, I generate right around 900psi.

At about 50%, maybe 700psi.

Engine at 100%, I see 1000psi.

This pressure is the same for any of the levers depressed.

From my limited knowledge, that pressure should be closer to 2000psi, should it not?

Is it a safe assumption that the pump is just weak? What are the options for an old Sherman pump. Can these be rebuilt? Are replacements available?

Thanks,

First impression is a worn out pump. Yes pressure dhould be much higher but 2000 PSI might be a bit high for a system of that vintage. Repeat that test with the gauge screwed directly into one of the work ports on the loader valve. That takes the cylinders out of the circuit.

Pump is cheap and easy to fix.

TOH

This post was edited by TheOldHokie on 05/12/2023 at 05:43 pm.

 

[Midwayman]

(quoted from post at 15:55:50



Pump is cheap and easy to fix.

TOH

This post was edited by TheOldHokie on 05/12/2023 at 05:43 pm.

Sounds good. I did some internet reading yesterday, and it sounds like that PTO speed on these 8n tractors is not optimal for these pumps. Someone mentioned that with the standard transmission, it will run slow. It sounds like something like a step up gear set for these would help.


So when you say cheap and easy fix, is the process of rebuilding a pump like this disassembling and putting in new seals? I am mechanically inclined with cars, but have to admit, I have never cracked open a hydraulic motor/pump.

I am about to go out and start the machine while cool to see if my gauge pressures are different when cool and digging better.

 

[8NChris]

Mine does that when the screen gets clogged. The screen is behind those 8? bolts where the suction hose goes to the tank. You can download the manual from the other N website.

 

[504]

Youll know more when you get the gauge on it. Bad
pump,bad suction hose, bad relief valve. On that
hydraulic only system I would use straight 10weight
motor oil or the cheapest hydraulic oil I could find. No
gears to protect just a pump.

 

[TheOldHokie]

(quoted from post at 08:57:24 05/13/23)

(quoted from post at 15:55:50



Pump is cheap and easy to fix.

TOH

This post was edited by TheOldHokie on 05/12/2023 at 05:43 pm.

Sounds good. I did some internet reading yesterday, and it sounds like that PTO speed on these 8n tractors is not optimal for these pumps. Someone mentioned that with the standard transmission, it will run slow. It sounds like something like a step up gear set for these would help.


So when you say cheap and easy fix, is the process of rebuilding a pump like this disassembling and putting in new seals? I am mechanically inclined with cars, but have to admit, I have never cracked open a hydraulic motor/pump.

I am about to go out and start the machine while cool to see if my gauge pressures are different when cool and digging better.

Gear pumps are not generally rebuildable and parts are not readily available. On a pump that old probably unobtanium. New gear pumps are $150. That said which pump setup do you have - straght coupled or planetary?

TOH

 

[Midwayman]

After some research, it sounds like this may be working exactly as intended. These seem to be known to be sluggish without a step-up transmission. In virgin clay, it makes the process pretty slow, and I have a couple fairly significant trenching projects coming up:


[b:25dc5f20f3]New questions based on information so far:[/b:25dc5f20f3]

1. Knowing that this problem gets significantly worse as the oil heats, is it possible that a different (higher viscosity) hydraulic oil would give better performance when warm? I have no idea what is in there now.

2. Is is possible to buy a new pump that would be better suited to the engine RPMS of the 8n?

3. Outside the box idea: This machine also has a wagner front loader (direct drive engine pump=higher RPMs). If a guy were to put quick disconnects and some kind of changeover valving, would using the loader pump be a more effective route to get good pressure for the hoe?


Thanks for the help so far!

 

[8NChris]

What model do you have? The wore out 54B100 I have is slower than a newer backhoe for sure. I don't have overdrive either but on this one a significant slow down when warm up isn't normal unless the filter is clogged. A starving pump will begin to whine when restricted. Tearing the pump apart or cleaning the reusable metal filter and screen, you'll get dirty either way.

 

[Midwayman]

Mine is a 54B900 (IIRC). My pump doesn't whine or give me any fits, just gets really lethargic. I have no idea how old or what type of fluid is in the tank, so perhaps taking off the screen, dumping fluid and refilling is in order.

Any kind of consensus on exactly what to use? I see Universal Tractor Fluid get thrown around for the front loader, any reason not to use the same on both?

Also, if you have a hookup on the manual for this Sherman 54B, I would love to get a copy.

Thanks!

 

[TheOldHokie]

(quoted from post at 12:24:12 05/15/23)
Mine is a 54B900 (IIRC). My pump doesn't whine or give me any fits, just gets really lethargic. I have no idea how old or what type of fluid is in the tank, so perhaps taking off the screen, dumping fluid and refilling is in order.

Any kind of consensus on exactly what to use? I see Universal Tractor Fluid get thrown around for the front loader, any reason not to use the same on both?

Also, if you have a hookup on the manual for this Sherman 54B, I would love to get a copy.

Thanks!

Your problem is low pressure and bypassing when the oil getd hot. That is not as designed and unlikely to be acfilter problem. Higher viscosity oil is an ineffective bandaid on a henmoraging pstient.

I am not familiar with the model numbers but sounds like is not the planetary (58C) model. Replacing that pump should beveasy and inexpensive. Increasingvthecdidplacement for higher flow is a possibilty.

Riunning the hoe off thev loader is also an easy and relatively inexpensive modification. Thats exactly how many modern TLBs are designed. They only issue I can forsee is the return line plumbing on the backhoe valve. You would need a new loader valve ($150) and some hose. It would eliminate the PTO pump and easily get you higher flow.

TOH

 

[8NChris]

(quoted from post at 09:24:12 05/15/23)
Mine is a 54B900 (IIRC). My pump doesn't whine or give me any fits, just gets really lethargic. I have no idea how old or what type of fluid is in the tank, so perhaps taking off the screen, dumping fluid and refilling is in order.

Any kind of consensus on exactly what to use? I see Universal Tractor Fluid get thrown around for the front loader, any reason not to use the same on both?

Also, if you have a hookup on the manual for this Sherman 54B, I would love to get a copy.

Thanks!

ith 13 post you can post photos now. Yours may have the triangle shaped pivot for the digger arm and the offset top bracket for the digger arm lift and bucket operation. That should be the same non bypass filter I have. Does your 900 still have the common stabilizer bar with one-way rams and use three point to retract it? Or are they two separate outriggers that use the same pressure hose?

If the pump doesn't whine like it is starving for fluid and your resuvuar isn't unusually full of bubbles you may have a worn pump like mentioned. Worn pump does get weak as mentioned but the drastic change between cold and warmed up leads me toward the screen. If you find all the old leather packing in the fine screen be sure to wipe it out of the last ¼" or so out of the bottom of the tank also. Enough of it falls out of the screen for it to work when it has been off for an hour or so and stirs back up when the in coming return fluid stirs it up.

This post was edited by 8NChris on 05/15/2023 at 01:19 pm.

 

[Blue Jay]

Send me an E-mail to get books on your power digger.

 

[Midwayman]

Blue Jay - Email sent.

8NChris - I took some pictures. It has the 1-piece outrigger that is controlled by the 3-point. If I can get a break, I will get the thing pulled up on the side of a hill and take out those bolts to see the status of that screen... didn't even know it had this.

[b:e57a3a886d]Any takers on the hydraulic fluid suggestions?[/b:e57a3a886d] Can I just buy universal tractor fluid and use in both the loader and hoe? 504 suggested 10weight motor oil. I also don't know how long the oil has been in there. Is there a good interval you guys use for hydraulic oil changes?

I am guessing the 54B900 on the dataplate is the correct version of the digger?


This post was edited by Midwayman on 05/16/2023 at 09:37 pm.

 

[TheOldHokie]

(quoted from post at 00:26:22 05/17/23) Blue Jay - Email sent.

8NChris - I took some pictures. It has the 1-piece outrigger that is controlled by the 3-point. If I can get a break, I will get the thing pulled up on the side of a hill and take out those bolts to see the status of that screen... didn't even know it had this.

[b:80bc96d344]Any takers on the hydraulic fluid suggestions?[/b:80bc96d344] Can I just buy universal tractor fluid and use in both the loader and hoe? 504 suggested 10weight motor oil. I also don't know how long the oil has been in there.

Is there a good interval you guys use for hydraulic oil changes

Ordinary ISO (AW) 32 or 46 hydraulic oil readily available at sny tractor supply. You can use same oil in loader and hoe. As I said earlier, easy to dump the PTO pump and run both off a common sump and the loader pump. Change at 400 hours.

TOH

This post was edited by TheOldHokie on 05/17/2023 at 03:07 am.

 

[TheOldHokie]

Here s a diagram of how to plumb the loader and backhoe togther. Its real simple:

• 
  [*:5130a1c94d]Run a hose from teh suction port on the backhoe tank to the inlet on the loader pump
  [*:5130a1c94d]Run a hose from the outlet port on the loader valve to the inlet port on the backhoe valve
  [/list:5130a1c94d]
  
  Thats it - done and the backhoe and loader will work full time and simulataneously off the loader pump and backhoe reservoir.
  
  Technically you should be using a loader valve with separate tank and power beyond ports as shown in the diagram. You can get one for $150 and it would be a major upgrade from the old Wagner valve. It would aklso let you install a REAL filter in teh tank return. Its not modern full flow filtering but its a lot better than what you have now.
  
  TOH
  
  
  
  
  

 

[Blue Jay]

E-mail has been sent back to you with link to manuals.

 

[8NChris]

I use 46 as others suggested. The suggested 10W would probably work better in a colder climate than this one lives. Yes you have the revised model of the 54B and looks to be very well treated compared to mine. It is down for a new arm and redesigned pivot. The 54C got a boxed digger arm and two out riggers.

 

[Midwayman]

Excellent information.

Blue Jay - Got the info. Already learned a thing or two.

TheOldHokie - Thank you for the explanation. I will heavily consider the upgraded loader valve with power beyond. My original doesn't actually seem to work very well. It sticks in certain spots and makes the pump whine a lot, particularly when actuating the bucket, almost like it isn't always making the circuits complete inside the block all the time.

Are these ebay units junk?: https://www.ebay.com/itm/3743428563...xju+iaH2uA4UXfAWqSGDZEfg==|tkp:Bk9SR9LXv9GFYg


I suppose before I get too far down the road, I should put a gauge on the loader pump... I can only pick just shy of 1000lbs which seems light. It uses a Cross pump, so I assume this was a later addition but may mean it can either be rebuilt or replaced without too much grief.


I use in cold and hot weather out here so I will get my hands on some AW32.

8NChris - Very cool. I like the 12" (?) bucket.