Traction main relief

   / main relief #1  

shoot2boot

New member
Joined
Jun 4, 2018
Messages
1
Tractor
mahindra max26xl
where is the main control valve and test port so i can check the pressure on a max 26xl its got 2hrs on it and the owners manual says if one tire spins stop and use diff lock but it wont spin a tire it just stalls . dealer is 140 miles away and is a really sorry one at that i read that some were low around 1800psi from the factory which it should be 2063psi. i cant find any info online i did find a place to buy a service manual and parts man. for $140.00
 
   / main relief #2  
I think the two are unrelated. The only external pressure adjustment that I know of is on the loader valve (typically). The loader valve will have a cap over an adjustment screw/nut etc.

But I’m guessing you are trying to push or move uphill in medium or high range. Or with the RPMs too low. I could be wrong- in which case it’s acting like it’s out of power- not hydraulic pressure.
 
   / main relief #4  
I will also say I agree that your in-operative diff lock is an issue all in itself. Does it engage and disengage on flat level ground with no rolling resistance normally?
 
   / main relief #5  
I will also say I agree that your in-operative diff lock is an issue all in itself. Does it engage and disengage on flat level ground with no rolling resistance normally?
Um, I didn't see anything that inferred the diff lock didn't work. He wasn't able to test it because he couldn't develop wheelspin. I assumed lack of wheelspin was power related, not due to an always-on diff lock.
 
   / main relief #6  
I guess you are right depending how you read that. Need more information to clarify. I read "but it wont spin a tire it just stalls" meaning that it stalls when he engages the diff lock. Your decipher would make more sense.

Now that I think more about it.. This is on an XL so assuming Shuttle not HST? But in any case, adjusting hydraulic pressures would have no affect transmission stall as the hydraulics are auxiliary. RNeumann might be on to something if he is not in LOW RANGE.
 
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   / main relief #7  
The 3 pt hitch will have its own relief and also safety valve.

The safety valve is a surprise to most owners. Its purpose is to deal with the shock loads when a heavy implement is hung off the 3 pt and you are bouncing over bumps.

The relief valve will have its own method of adjusting its pressure.

The safety valve will not need any adjustment. It is tested by removing it and using a fuel injector tester to subject it to higher pressures that the hydraulic pump can produce.

Dave M7040
 
   / main relief #8  
Not trying to hijack the thread but does the main relief in the hydraulic block set the system pressure to the hst, 3pt hitch and the loader control valve the the relief in the loader control valve sets the pressure to the fel
 
   / main relief #9  
Not trying to hijack the thread but does the main relief in the hydraulic block set the system pressure to the hst, 3pt hitch and the loader control valve the the relief in the loader control valve sets the pressure to the fel

It is a fairly simple concept.

The first relief valve in a circuit sets the max pressure for any other relief valve further along the path to the reservoir.

A hypothetical circuit which sees the pump first go to the FEL, which has a relief valve, and then through a power beyond port on the FEL valve to the 3 pt and rear remotes.

If the FEL relief (the first in the circuit) is set for 2,200 psi, the relief for the 3 pt and rear remotes, no matter how high you try and set it, will not be supplied with pressure any higher than the relief in the FEL valve block i.e. 2,200. The relief for the 3 pt and rear remotes can be set lower, say 2,000 psi.

The first relief limits the max pressure at any point further along the circuit.

If this is not clear plse ask more questions

Dave M7040
 
   / main relief #10  
Thanks Dave. I understand. I can’t find any diagrams or schematics of the hydraulics and was trying to figure out if the relief in the block is the first in the system that sets the pressure to the hst,pto etc. Guess I’ll just go out and trace the pump discharge to see where it goes.
 

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