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Discussion Starter · #1 ·
Tom - I have joined this forum per your invite. Greetings to you and ALL

Here's my story.
I have very recently acquired a 1973 Case 644 Loader (sn 9662751)
Tractors history:
Re-powered in 2004 with 16hp Vanguard
Hydraulic Pump replaced (possibly in 2004)
Hydraulic Drive Motor rebuilt (possibly in 2004)

Symptom's:
- In high or low gear, forward motion power OK, but slows on incline - reverse VERY weak.
- as the tractor warms up (5-10 minutes), the forward motion power weakens and reverse all but does away.
- wether the tractor is cold or warm, the Front End Loader seams to work fine, the hydraulic pumps whines but it does not seam to suffer any power loss.

What I have done so far:
-I have replaced the trans-axel fluid with 80w90 EP Gear Lubricant
-I replaced 5 of the 12 quarts of the hydraulic oil with 15w-40 Rotella T. The previous owner had placed a drain valve on the supply hose off the oil reservoir and I drained what I could there. I'm skitish about any of the other hydraulic hoses and valves being under pressure and not sure how to approach...
-Ordered replacement control plate (should receive this week), old one is very warn.
-Ordered used Hydraulic Drive motor from ebay that came off a 1974 Case 446 w/Onan, sn 9697237 - should have this week.

If these two items I have ordered don't fix the issue, then I guess I'll need a control valve (or should I try adjusting the relief valve on the control valve and if so, how?)
Does anyone know where a control valve could be had? According to the Parts Manual, the control valve part number is C21497 or C19221

Another wish would be to find a 3-point hitch for this tractor, and lastly, it does have the ram for the mower deck - but no mower deck which I don't want anyway).
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

silvertogold said:
Tom - I have joined this forum per your invite. Greetings to you and ALL

Welcome to the forum, STG. We will do our best to help you get your loader back into working condition.

Here's my story.
I have very recently acquired a 1973 Case 644 Loader (sn 9662751)
Tractors history:
Re-powered in 2004 with 16hp Vanguard
Hydraulic Pump replaced (possibly in 2004)
Hydraulic Drive Motor rebuilt (possibly in 2004)

How do you know to a certainty that the pump was replaced and the drive motor was rebuilt?

Symptom's:
- In high or low gear, forward motion power OK, but slows on incline - reverse VERY weak.
- as the tractor warms up (5-10 minutes), the forward motion power weakens and reverse all but does away.
- wether the tractor is cold or warm, the Front End Loader seams to work fine, the hydraulic pumps whines but it does not seam to suffer any power loss.

What I have done so far:
-I have replaced the trans-axel fluid with 80w90 EP Gear Lubricant
-I replaced 5 of the 12 quarts of the hydraulic oil with 15w-40 Rotella T. The previous owner had placed a drain valve on the supply hose off the oil reservoir and I drained what I could there. I'm skitish about any of the other hydraulic hoses and valves being under pressure and not sure how to approach...

I suggest that you acquaint yourself with our Technical Library. In particular, the FAQ's. To help you out, here is the link to a document that you should find very helpful.
-Ordered replacement control plate (should receive this week), old one is very worn.
-Ordered used Hydraulic Drive motor from ebay that came off a 1974 Case 446 w/Onan, sn 9697237 - should have this week.

The problem with buying a motor that is 37 years old is that it might not be any better than the one you already have.

If these two items I have ordered don't fix the issue, then I guess I'll need a control valve (or should I try adjusting the relief valve on the control valve and if so, how?) No.... you should NOT touch the relief valve until such time certain tests have been performed and you begin to understand what you are doing.

This is where I have to tell you STOP. You are going about this in the same way some so-called garage mechanics do. They just keep throwing parts at the vehicle at the owner's expense until the problem gets cured. You need to SLOW DOWN, work with us, learn some things about hydraulics and diagnose the real problem.

Does anyone know where a control valve could be had? According to the Parts Manual, the control valve part number is C21497 or C19221

Control valve RARELY fail. They are last on the list of "usual suspects".

Another wish would be to find a 3-point hitch for this tractor, and lastly, it does have the ram for the mower deck - but no mower deck which I don't want anyway).
All of the 600 series tractors came with the mid-lift cylinder so that the owner could cut grass. Finding a LT-26 3 pt hitch is difficult because not many of these tractors get parted out and when one of those hitches shows up on e-Bay, it is fought over pretty hard. You might get lucky eventually but I suggest that you also watch for a HH-34 hitch and purchase that instead. I have to tell you that a new HH-34 costs more than a grand at a dealer and will often bring $500.00 and up on the used market. If your tractor does not have the rear PTO for the hydraulics, that too is a rare item to come across but if you want to power hydraulic attachments, then it is necessary.

The new banana plate is a good move but you may also have wear and tear in other parts that work in conjunction with the banana plate. Dismissing what looks to be "minor wear" on parts is a huge mistake. If you want to make the spool in the travel valve move fully in and fully out smoothly and under total control, then you need to be diligent in replacing or repairing all parts that are worn. Keep in mind that the spool does not travel very far in totality and that a portion of that travel controls forward while another portion controls reverse and there is a neutral spot in between.

We also have no idea what hydraulic pump was installed or if the pump was new or used......... or do we?

If the drive motor was truly rebuilt by a competent hydraulics shop just a few years ago, then it should not need replacing. In order to find the real problem, the first thing you need to do is to properly drain your hydraulic system in accordance with the document I linked you to. The oil in your tractor is just as vital a component as the motor and pump are. You have no idea what was in this tractor when you bought it. You need to start FRESH with new oil in the system EVERYWHERE. The document explains how to do that and until you accomplish that task, you are whistling in the dark. Then, you need to address the banana plate and linkage issues to make sure the spool is moving 100 percent into the valve body and 100 percent out. If your problem is not solved by then, I will tell you where you can buy a test gauge set up for less than $100.00 so that both of us will know what that pump you have is capable of producing in the way of pressure. At that point, we may try something with the relief setting but let's cross that bridge when we get to it. As I suggested on YT, you should go to Walmart and buy a 5 gallon pail of Rotella 15/40 and then get on with the messy job of draining all of the oil.
 

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Discussion Starter · #4 ·
Re: 1973 Case 644 - loosing power at wheels, not at loader

Thanks Maynard!

Tom - That was an unexpectedly fast response - WOW!

I know the pump was replaced and the drive motor was rebuilt because I have the receipts from the original owner, I agree with you that competence of the shop that did the work is always suspect.

I did review the technical FAQ and admit I may need to obtain help with the hydraulic oil draining since I have been cautioned by many that there 'could' be parts of the system under extreme pressure and I admit I'm a bit nervous about those parts of it. The previous owner did tell me he changed the oil recently so I had used the same stuff, but perhaps he only changed some as I did. I will get some more oil as you suggest for this undertaking. Would bad oil effect the hydraulic drive motor differently than the loader components?

I will re-inspect all the associated control plate linkage as you suggest. I could understand how a worn control (banana) plate and associated linkage effects travel of the control valve, which would effect speed of the hydraulic motor, but I have difficulty seeing how those mechanical deficiencies could effect drivability performance as the tractor warms up, that is why I was thinking hydraulic drive motor or control valve. I could be wrong here but I ruled out the hydraulic pump because the loader performance does not degrade.

The reason I had inquired about the relief valve is that it's mentioned in the "Troubleshooting the Hydraulic System Manual 9-50632" that I found on a web site. But if you say to stay away from that, at least for now, I will not touch it.

When I get that control plate installed, as well as gone through all the associated linkage, and change the hydraulic oil, I'll get back to you with those results and I guess we'll take it from there.

thanks so much!!
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

Welcome to site
I bought 646-78 with same problem oil heat up reverse weak adjusted linkage so spool in valve bank shift all way both ways. Now bump throttle above Idle and spin in reverse and forward when oil warm with full weight box on back. Now I have these little holes all on land wheel spin.
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

Nothing is going to be under extreme pressure unless the engine is running. You're not going to hurt anything if you have to loosen a hydraulic line here and there.
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

silvertogold said:
Thanks Maynard!

Tom - That was an unexpectedly fast response - WOW!

I know the pump was replaced and the drive motor was rebuilt because I have the receipts from the original owner, I agree with you that competence of the shop that did the work is always suspect.

I did review the technical FAQ and admit I may need to obtain help with the hydraulic oil draining since I have been cautioned by many that there 'could' be parts of the system under extreme pressure and I admit I'm a bit nervous about those parts of it.

As my partner Snotrocket so correctly pointed out, nothing is under high pressure if the engine is shut off. If you follow the directions in the FAQ and support the loader arms properly, then the weight of the arms will not create any pressure on the lift cylinders when you remove the lines to those cylinders. This is all about getting as much of the suspect oil out of the system. If you drain all the cylinders including the mid-lift one, then you will have about a quart at the most residing in the rest of the system. That amount is not enough to cause you grief.

The previous owner did tell me he changed the oil recently so I had used the same stuff, but perhaps he only changed some as I did. I will get some more oil as you suggest for this undertaking. Would bad oil effect the hydraulic drive motor differently than the loader components?

The drive motor must have oil of a certain viscosity that will remain at that viscosity as it warms up. Many oils that are labelled "hydraulic fluid" are often found to be the equivalent to 5 weight motor oil which will easily bypass the internals of the special motor that is used to drive these tractors. The more the oil heats up, the more it bypasses. This is why it is imperative for you to carry out the procedure outlined in that document because we cannot judge the performance of the system if the oil is incorrect.

I will re-inspect all the associated control plate linkage as you suggest. I could understand how a worn control (banana) plate and associated linkage effects travel of the control valve, which would effect speed of the hydraulic motor, but I have difficulty seeing how those mechanical deficiencies could effect drivability performance as the tractor warms up, that is why I was thinking hydraulic drive motor or control valve. I could be wrong here but I ruled out the hydraulic pump because the loader performance does not degrade.

The pump in this tractor flows oil to every part of the hydraulic system and every part of the system has its own relief valve. If you have a rear PTO valve, that valve has a relief built into it that is supposed to be set to open up if the pressure in the system exceeds 2300 PSI. The travel valve also has a relief that is set at 2100 PSI but the mid-lift valves relief is set at less than 1000 PSI on the loaders. You have a double spool valve that looks after the loader functions and it has a relief that is set at 1200 PSI.

In other words, a worn pump may be able to produce 1400 PSI with no problem, thus allowing the loader to function perfectly but the travel aspect of the tractor is severely hampered at that pressure.


The reason I had inquired about the relief valve is that it's mentioned in the "Troubleshooting the Hydraulic System Manual 9-50632" that I found on a web site. But if you say to stay away from that, at least for now, I will not touch it.

Reliefs are installed in the system to protect the hydraulic components, the metal items they are anchored to at each end of cylinders and to keep the pump from destroying itself. It is premature to touch the relief because those rarely give any problems due to their simplicity. The spring would have to either break or lose a substantial amount of tension in order for it to open up at a much lower system pressure. There is a sequence of steps to diagnose the problem and it is wise to stick with it.

When I get that control plate installed, as well as gone through all the associated linkage, and change the hydraulic oil, I'll get back to you with those results and I guess we'll take it from there.

thanks so much!!
You are welcome. We are here for you when you are ready to proceed. Something tells me that you may notice an improvement once you have completed the oil change and then again after repairing the travel linkage. This may turn out to be multiple issues, not just a single one.
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

I had same problem on my 646. Listen to Hydriv. He is the guru of these tractors.

My banana plate was worn. Got on this site and done much reading of past posts. Adjusted control forward/reverse linkages with some improvements. Found if I pushed shift lever forward up and held it, I got more power to the wheels. So I removed banana plate and built it up by welding and surface grinding it back. The lower bracket that is bolted to frame was worn real bad. Welded it up and ground back out. Made a new slide pin as it too was worn down. Now have all kinds of power to wheels. A hour of work and no expense to correct my sluggish drive.
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

silvertogold said:
y'all are awesome!

I'm so xcited by all the info and support I need to take a shower :lol:
STG,
I must caution you to keep yourself under control at all times. If you have a wife or GF in your life and she notices your excitement while you are on your computer, it could cause serious relationship problems. :sidelaugh:

Here is another thread that contains an article authored by one of our Team members that you may find interesting.

viewtopic.php?f=7&t=270&p=2455#p2455
 

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Discussion Starter · #11 ·
Re: 1973 Case 644 - loosing power at wheels, not at loader

Update...

I finally received the replacement control arm, which also came with the 'valve control' and 'guide' bracket assembly.
these items were installed, and the hydraulic oil was changed.

I then proceeded to make adjustments to the spool valve via the valve control rod nuts for the forward/reverse. This turns out to be a very finicky adjustment...to far one way and the tractor moves forward (without pedal) when the direction control lever is in forward and little or no reverse when in the opposite adjustment range.

Regardless, there was no noticeable improvement in performance when the adjustment was finally where I believe it should have been.

What I did notice, was that the spool valve for the direction control is sticking and seamed to pop out when making adjustments on more than one occasion.

Does this sound like the Hydraulic Control Valve Assembly that needs to be rebuilt or replaced?

Anyone know where one can be had? (Part Number C19221)
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

The time has come for you to find out how much pressure your pump can put out. Do you have the rear mounted PTO valve on this tractor?
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

Too bad... it would have made life easier for both of us. :sidelaugh:

Here is a link that will take you to Northern Tool and they are just one company out of many that can supply you with a glycerin-filled pressure gauge that reads zero to 5000 PSI or zero to 3000 PSI. Ignore what it says on the dial of the gauge in the photo. That pic is for illustration purposes only.

http://www.northerntool.com/shop/tools/ ... 8251_48251

You have already located your travel/lift valve on your tractor. On the underside of that casting, you will find a hexagon hole in a pipe plug. This is the drain port and also the test port. If you followed the instructions in the document I referred you to, this plug should be familiar to you already. You need a four foot length of the smallest diameter hydraulic hose that has a working pressure of at least 3000 PSI to go between the gauge and this test plug. This will allow you temporarily secure the gauge to one side of your tractor so you can watch it while performing the test I am about to outline.

You will also need a few fittings to connect the hose to the gauge at one end and connect the hose to the test port at the other end. Any decent, local hydraulics shop should be able to help you put this test apparatus together. The purpose here is actually multi-fold. You need to find out what the max pressure your pump is developing when asked to perform the hardest task and the gauge will also allow you to correctly set the various relief valves in your tractor SAFELY.

Once you get the gauge, hose and fittings assembled and installed to the test port, you need to move the tractor to a location that has dry pavement of some kind for maximum traction along with an object that cannot be moved by the tractor pushing against it. That could be the poured concrete wall of your home or a very large tree that you protect with a piece of lumber between the bark and the edge of the bucket.

You will put the tractor's trans-axle in High Range to make it tougher on the tractor and less tough on the object you are pushing against. With the bucket up against that item, open the throttle wide and while watching the gauge, step on the travel pedal with the travel lever all the way forward. The pressure should climb as you push the pedal to the floor. What is the peak pressure noted on the gauge?

When you determine that figure, come back here and post it so we can help you further.

If everything was operating A-OK, then the gauge should read 2300 PSI and you should hear the relief valve squealing like a stuck pig. The reading you ultimately get will help to determine the next step.

One more thing. The travel/lift valve in the 600 Series tractors are different than the ones used in the 200/400 Series tractors. Since very few 600's get parted out, finding a used valve is very tough and they are often fought over very hard on e-Bay. A new valve from Eastman would likely be $700.00. I know that you are wanting to do this quickly but........ it just isn't that simple. Proper diagnosis is a step by step process and this is the next step.
 

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Discussion Starter · #15 ·
Re: 1973 Case 644 - loosing power at wheels, not at loader

Well I did as advised,

I purchased the pressure gauge, hose and fittings, installed into the drain/test port on the travel control valve and proceeded to a collision course with a massive oak tree.

When the tractor was cold (within one minute after starting up cold), the PSI went to about 2100-2150 but the tires did not spin :sad: , I drove the tractor around for 10 minutes and repeated the tree test and the pressure registered 1500-1600, with no tire spin of course.

I have left the pressure gauge test fixture attached to the travel control valve awaiting instructions.

FYI, I have secured a hydraulic drive motor which came off a 400 series, it is in my possession but I have not yet installed it per earlier advise. I have also secured a travel control valve (being shipped) that came off a 600 series tractor. both items were purchased at very reasonable cost(s). If I do not need these I have spares :fingerscrossed: .
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

Cold oil always gives higher reading than warm does. However......you drained the entire system and installed the correct oil. Therefore, if your pump was good it would give you 2100 PSI with warm oil.

So... let's talk about the relief valve that had you concerned. If the relief spring was broken or if the ball was being held off of its seat, then you would NOT have got 2100 PSI readings. We did not want the tires to spin. We wanted the tires to stand their ground and create the maximum resistance to the oil and cause the highest pressure reading possible......right up to the setting of the relief setting. A worn pump allows oil to get past clearances inside the pump from the OUT side back to the IN side of the pump.. As the pressure climbs, a greater percentage of the thinned oil gets past those clearances.

If you wish..... go and change out the drive motor and see what happens. I think that YOU need to do this in order to settle that issue in your own mind. The same holds true with the travel/lift valve. If you wish to swap it out too, then take the plunge. You have the test gauge setup now. You've done the tests. You now have a benchmark to go by. My money is on this alleged "new" pump being the culprit but since you already have these other parts, its only your time a quart of oil at issue.

Just make sure that you wash off all dirt and other crap before opening up any part of the system. You do not want any contamination getting into your system. Flush the motor and valve with either fresh oil or new cleaning solvent. All I can do is react to what you tell me and advise you what steps to take. At this point, I've taken you as far as I can. The next decision/s are totally up to you. A new pump is $200.00 roughly from Grainger (4F667 comes to mind) . Your pump SHOULD be a Type A style. You want an internal displacement of about .61 to .65 cubic inches. The pump must be capable of 3000 PSI working pressure and able to spin at 3600 RPM at minimum.

What would you like to do?
 

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Discussion Starter · #17 ·
Re: 1973 Case 644 - loosing power at wheels, not at loader

The hydraulic pump in this tractor has a nameplate with the following info:

Interchange. LLC.
Culpeper, VA
HB21258
40753

I tried to look it up and what I found so far is that Interchange, LLC leads ti a web site www.hydraulic.net. I sent them an email with that information and have requested information on that pump, if nothing else to see if it meets the requirements you outlined.

When (if) I hear back from then I'll re-post.

Thanks!
 

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Discussion Starter · #18 ·
Re: 1973 Case 644 - loosing power at wheels, not at loader

one more observation.

This tractor was re-powered with a Briggs and Stratton 16HP Vanguard.
The info that I could research on that engine is

Model 303447 (30 cubic inch, Design Series 3, Horizontal Crankshaft, Ball Bearing Flange Mounting Preassure Lubrication, Electric Starter 12V Gear Drive with Alternator)

Type 1272-E1 (??)

Code 0306261 (date code June 26, 2003)

RPM is believed to be 3300

Not sure, but if the RPM's can only obtain 3300, could this be part of the issue?
 

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Re: 1973 Case 644 - loosing power at wheels, not at loader

The engine RPM would affect the total gallons per minute of the pump but not it's ability to create pressure when called upon to do so. The lower engine RPM would not affect your loader noticeably but there would be a slight reduction in ground speed and if you had a rear PTO, then implements with motors would also turn a bit slower.

3300 RPM is an odd speed for it to be governed at. Perhaps the engine was spec'd for a certain piece of equipment and there were a bunch of surplus engines as a result.

Let's see what the pump guys come back with.
 
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