Hydraulic Pump Allis Chalmers C
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209160
Printed Date: 25 Jan 2026 at 7:05am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Hydraulic Pump Allis Chalmers C
Posted By: John426
Subject: Hydraulic Pump Allis Chalmers C
Date Posted: 30 Nov 2025 at 10:49am
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Hi On the hydraulic pump of the model C ; there are 4 balls - 2 balls for intake valve item 27 , ref number 70915904 , 5/16" , is it correct? - Another one are the 2 discharge valve ball. Also 70915904 , 5/16" , is it correct? - And the last, Releif Valve item N° 7 reference 70915906 . This should be smaller only 3/16" does this size correct ( the others are 5/16")    ? |
Replies:
Posted By: steve(ill)
Date Posted: 30 Nov 2025 at 3:46pm
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i think #3 and #21 ( intake and discharge) are the same size... #10 is smaller.. i dont remember the diameter. ------------- Like them all, but love the "B"s. |
Posted By: Alvin M
Date Posted: 30 Nov 2025 at 3:51pm
| Takes 4 70915904 Balls for intake and discharge 5/16 and 1 70915906 for relief valve 3/16 |
Posted By: John426
Date Posted: 01 Dec 2025 at 3:09am
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When the pressure ot 3200 PSI is correct. But the implement on the lift doesn't stay on the hold position. Does it means that the Relief valve is leaking? What is the symptom of a Discharge valve leakage? The manual says : pressure is 3100 lbs. on properly functionning pump , .... there will be a slow dropping of pressure .... the pressure become stationary at 1500 lbs. Does this means that the normal hold pressure for the implement up is 1500 lbs, for example during transport or everything else. So to be clear and well understand. The lifting force would be at 3200 lbs, and then the load holding force would be lower at only 1500 lbs. Is it correct?
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Posted By: John426
Date Posted: 06 Dec 2025 at 11:27am
| Does this correct understanding ? The lifting force would be at 3200 lbs, and then the load holding force would be lower at only 1500 lbs. Is it correct? |
Posted By: steve(ill)
Date Posted: 06 Dec 2025 at 12:18pm
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the lifting pressure you would see is only what it takes to overcome the WEIGHT of the implement.. If you raise all the way to the TOP and STALL OUT THE PUMP , then you will see 3200 psi..... If your lifting something like 300 pound disc, it may take 1000 psi to lift it... if your lifting 600 pounds it might take 2000 psi... if your lifting 900 pounds it might take 3000 psi... If you try to lift 1000 pounds the pump might stall out, go over relief and the gauge would read 3200 psi and the disc may not lift at all.. the HOLD pressure is only what it takes to HOLD the disc up on position.. ------------- Like them all, but love the "B"s. |
Posted By: John426
Date Posted: 06 Dec 2025 at 1:27pm
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Yes Steve. I understand that. My trouble is that the manual says hold pressure 1500PSi. If i take your example if the implement is 600pounds, need 2000PSI to hold for the transport. Does the system will able to maintien up the implement? This compare to the 1500PSI hold pressure ? |
Posted By: steve(ill)
Date Posted: 06 Dec 2025 at 8:45pm
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i have never heard of the 1500 psi hold pressure.. I thought the valve would hold any pressure under 3200 psi... depending on the WEIGHT of the implement.. All of my implements will stay FIXED and not drop in the hold position.. Of course none of them weights more than about 400 pounds. ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 06 Dec 2025 at 9:00pm
the valve does not have a 1500 psi set point or hold pressure. I think what the book is saying is the valve has some INTERNAL CLEARANCES and the pressure will leak off slowly from 3200 psi.. If the weight of the implement causes the pressure to continue to fall below 1500 ( after a period of time), then the internal clearances on the check balls and spools is getting out of SPEC.... How "FAST" it leaks off and if that is "OK" is determined by the operator... Most of my implements weigh less than 400 pounds and will stay up ovoer an hour ( some several hours)... if it leaks off in 2-3 minutes that might be a problem for some.. ------------- Like them all, but love the "B"s. |
Posted By: John426
Date Posted: 07 Dec 2025 at 12:58am
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OK it is clear for me now. Thanks
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Posted By: Alex09(WI)
Date Posted: 09 Dec 2025 at 9:28pm
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Those pictures are from an I&T manual. You can throw that manual in the woodstove, then purchase the OEM manual printed by Allis-Chalmers. That will have the correct specs and is more thorough compared to the I&T manual. ------------- www.awtractor.com A&W TRACTOR 920-598-1287 KEEPING ALLIS-CHALMERS IN THE FIELDS THROUGH THE 21ST CENTURY |