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4020 3 pt hitch

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Larry

02-25-2000 07:02:49




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I still have not found the hydralic problem with the the 3pt hitch on a early 4020. I have pressure at the line to the rockshaft control valve and 1500 lbs at the remote outlets. The 3 pt hitch will not respond at all. Is there an easy way to deturmin if it is a valve problem or a rockshaft cylinder problem? The linkage seems ok. I have not tried removing the valves in the control housing. Is it possible one is stuck? Thanks in advance!

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Linwood

02-25-2000 09:52:24




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 Re: 4020 3 pt hitch in reply to Larry, 02-25-2000 07:02:49  
If you only have 1500# at the remote, you won't have enough oil flow to work the rockshaft, as the first 1750# of pressure is diverted to the prioity system [steering, brakes] by the pressure control valve [prioity valve]. The 1500# you are reading is only what can leak by the pressure control valve and has almost no flow. Should be at least 2250# at the remote. The rockshaft valves give very little trouble.

Remove the filter and crank the engine over, if you have a good flow from oil filter housing to a bucket the problem is likely in the main pump. There are a lot other things that would cause the problem, but try this first.

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twopop

02-25-2000 11:43:59




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 Re: Re: 4020 3 pt hitch in reply to Linwood, 02-25-2000 09:52:24  
I RESPECTIVELY DISAGREE WITH THE STATEMENT THAT THERE IS NOT ENOUGH PRESSURE AVAILABLE AT THE ROCKSHAFT.THO IT IS TRUE THAT THE PRIORITY VALVE DIRECTS THE OIL FIRST TO THE STEERING AND BRAKES,THIS IS TRUE ONLY WHEN THE STEERING OR BRAKES ARE BEING USED, SO IF THE TRACTOR IS SITTING STILL WITH NO IMPLEMENT ON THE 3 POINT,THE 3 POINT SHOULD LIFT EVEN WITH ONLY AS MUCH AS 3 OR 400 LBS PRESSURE.. THE MAIN PUMP DOES HAVE A ADJUSTMENT SCREW THAT WILL ALLOW THE INCREASE OF PRESSURE.I BELIEVE THE PROBLEM IS IN EITHER THE CONTROL ARM SHAFT OR THE DRAFT CONTROL LINKAGE INSIDE THE CONTROL VALVE

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Dave Wickman

02-25-2000 13:18:54




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 Re: Re: Re: 4020 3 pt hitch in reply to twopop, 02-25-2000 11:43:59  
I would say Linwood is on the right path and the reason being is: With a closed center system the "Pressure Control Valve" (which protects steering and brakes) is acting as a gate in the system and the pump is destroking before it will flow any oil out to the rockshaft circuit. It takes oil flow to raise the rockshaft and without enough pressure to open the pressure control valve (or gate) the pump will destroke and not flow any oil. I would NOT touch the rockshaft in any way of repair until the system pressure was up to spec. There is a pressure adjustment on the pump but I would be willing to bet if system pressure is that low it will require a new stroke control valve in the pump to make it adjust up to that level. The steering and brakes will still function with the system pressure that low. The steering and brake systems are supplied oil before the pressure control valve. Hope this will help, holler back if it don't. Dave Wickman

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kraig

07-04-2003 23:34:37




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 Re: Re: Re: Re: 4020 3 pt hitch in reply to Dave Wickman, 02-25-2000 13:18:54  
Will the draft control knob effect the lifting, seems I remember moving the knob one time and it made it work, (not really sure any other opinions?)



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twopop

02-25-2000 08:23:05




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 Re: 4020 3 pt hitch in reply to Larry, 02-25-2000 07:02:49  
DID YOU AT ANY TIM REMOVE THE CONTROL CABLE FROM THE CONTROL LEVER AT THE ROCKSHAFT HOUSING.IF SO IT IS POSSIBLE THE CONTROL LEVER IS OUT OF ADJUSTMENT



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twopop

02-25-2000 08:34:41




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 Re: Re: 4020 3 pt hitch in reply to twopop, 02-25-2000 08:23:05  
ALSO HAS THE CONTROL VALVE BEEN REMOVED FROM THE ROCKSHAFT HOUSING OR THE ROCKSHAFT BEEN REMOVED FROM THE TRACTOR IF SO THE LOAD CONTROL ARM COULD BE IN THE WRONG PLACE AND CAN NOT RAISE,IS THE DRAFT CONTROL LEVER IN THE UPPERMOST POSITION



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Larry

02-25-2000 16:44:43




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 Re: Re: Re: 4020 3 pt hitch in reply to twopop, 02-25-2000 08:34:41  
I had the control cable off of the control valve and ended up removing the rockshaft control valve housing to make sure that it had not gotten out of time. I checked it with the manual to verify. I belive the linkage is OK. To see if I had pressure to the valve housing I took loose the hydralic line at the fitting on the housing then started the tractor, sprayed hydralic fluid about 30 feet from the loose fitting.

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twopop

02-25-2000 18:18:49




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 Re: Re: Re: Re: 4020 3 pt hitch in reply to Larry, 02-25-2000 16:44:43  
I HAVE AN I&T MANUAL. IF YOURS IS THE SAME?ON PAGE 78 FIG.224 IT SHOWS ITEM #7 FOLLOWER IF WHEN YOU OR SOMEONE ELSE TOOK OF THE CONTROL VALVE AND DID NOT LOCATE THIS PROPERLY ALONG WITH THE LOAD SELECTOR ARM IN THE CONTROL VALVE THE 3 POINT WILL NOT LIFT



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