JD2750 MFWD w/loader hydraulics get weak after short time running

   / JD2750 MFWD w/loader hydraulics get weak after short time running #1  

applepickr

New member
Joined
Jan 29, 2014
Messages
5
Location
Martins Mill, TX
Tractor
John Deere 2355 (2)/4250/6x4 & CX gators/1830/2140/2750mfwd/2755
I have an older 2750 MFWD with a loader that the hydraulics get very slow after running a short time and/or it warms up. We have recently replaced the transmission pump because it was leaking and all diagnostics pointed to front hydraulic pump so we replaced that also with a tested fully rebuilt one that was set to the same pressure specs as the one we removed. The hydraulics are great and fast (loader) when you first start it then they get slower and then the fwd will not switch out of 4x4. I hate to give up on this work horse, but it is becoming a money pit and not fixed.
 
   / JD2750 MFWD w/loader hydraulics get weak after short time running #2  
Who performed the hyd diagnostics? Over the yrs many hyd pumps have been replaced only to determine that the replaced pump wasn't the problem. Your tractor symptoms sounds typical for an internal hyd leak.

How many hrs of use since hyd filter was changed & suction screen(item 30) checked/cleaned? While hyd oil is drained would also be a good time to check hyd filter relief valve(item 18-20) to be sure it's not stuck open. JD utility tractors with hyd hi-lo & hyd pto have a history of supply tubes &/or seals failing. One can remove trans shift cover & apply compressed air to each tube & listen for escaping air. What type hyd control valve operates loader & how is it attached to tractor hyd's.
 

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   / JD2750 MFWD w/loader hydraulics get weak after short time running
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#3  
Thanks for the ideas, I will share this with our mechanic that is working on it. We bought it at an auction and it sprung a leak in the middle which ended up being a bad transmission pump which has been replaced. He got it back together and then the hydraulics seemed fine until it got warm the first time we used it. He is working with a retired JD mechanic and he told him to check the pressures and what they should be which led to the front hyd pump and we have now replaced that as well.
 
   / JD2750 MFWD w/loader hydraulics get weak after short time running
  • Thread Starter
#4  
Who performed the hyd diagnostics? Over the yrs many hyd pumps have been replaced only to determine that the replaced pump wasn't the problem. Your tractor symptoms sounds typical for an internal hyd leak.

How many hrs of use since hyd filter was changed & suction screen(item 30) checked/cleaned? While hyd oil is drained would also be a good time to check hyd filter relief valve(item 18-20) to be sure it's not stuck open. JD utility tractors with hyd hi-lo & hyd pto have a history of supply tubes &/or seals failing. One can remove trans shift cover & apply compressed air to each tube & listen for escaping air. What type hyd control valve operates loader & how is it attached to tractor hyd's.
We will try to get pics of those things and post for more ideas.
 
   / JD2750 MFWD w/loader hydraulics get weak after short time running #5  
I was employed at a JD dealer from '65-'87 & served at this dealership as a "hands on service manager" the last 13 yrs of employment. It's very important you reveal the type of hyd valve that controls front end loader & how it's attached to tractor hyd's. Majority of JD utility tractors built from '65-'92 had closed-center hyd systems that were very similar in operation which includes your 2750.

Also a simple test that you can perform is after tractor hyd oil is at operating temp with 3 pt fully raised/engine operating look inside hyd filler hole behind seat for spraying/moving oil. Spraying oil indicates faulty rockshaft control valve seals which will affect hyd performance. Have you tested hyd with pto in both on & off positions? Does your tractor have options of hyd hi-lo or reverser?
 
   / JD2750 MFWD w/loader hydraulics get weak after short time running
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#6  

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   / JD2750 MFWD w/loader hydraulics get weak after short time running #7  
FEL valve hoses are attached correctly to your tractor. I suggest to check to determine if FEL control valve is designed for closed center hyd system. You can perform a test by disconnecting return hose(see photo below) from hyd filter cover & cap fitting on filter cover. Then with both FEL control valve levers in neutral, aim open FEL valve return hose in a bucket then start engine & NO oil should exit hose.
 

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   / JD2750 MFWD w/loader hydraulics get weak after short time running
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#8  
The tractor does have a hi/lo switch on it. All the ideas/tests you have given us have passed or been okay per my mechanic. Any other ideas that might involve the hi/lo stuff or maybe the loader itself? I really don't want to sell it, but I am running out of time and patience.

Thanks for all your help so far. Sorry for the long delay, we have been trying to finish hay and moving cattle. (we are DONE with hay now)
 
   / JD2750 MFWD w/loader hydraulics get weak after short time running #9  
You're welcome.
Ok so when FEL control valve return hose was disconnected from ported filter cover & filter cover orifice capped then engine started with fel control spools in neutral ""no oil exited open return hose""?? Does pto on or off affect operation of hyd's? Please check your PM box for my message
 
 
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