Go Bottom4 way vs 3 way loader valve for snow blower
 | domogala
Join Date: Apr 2004 Posts: 34 Windham, NH 
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2005-11-10 119192
I am in the market for a B2782 snow blower for my B2910. The blower with the hydraulic rotating chute option requires a 4-way loader valve (B2079). My LA402 loader is from 2001 and only has a 3-way loader valve on it. So, what is the difference between a 3-way and 4-way valve, and why would it be necessary? I've been hunting the internet for an answer to no avail.
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 | Gearhead
Join Date: Jul 2005 Posts: 75 SEVEN mILE OH
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2005-11-10 119210
Lets see if i can get thic right. The valves you are talkin about are 3 and 4 position valves. 3 position valve only has 3 functions with 2 spools, up and down on one and curl and dump on the other. The up and down are 2 functions and the bucket spool is the third because it puts the fluid back into the opposite side of the cylinder when operated ....
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| Gearhead
Join Date: Jul 2005 Posts: 75 SEVEN mILE OH
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2005-11-10 119211
The 4 position valve has 2 functions on the bucket spool, onr that regenerates the fliud to the cylinder and one that lets it out of the cylinder these are only in the dump position. If you push the handle to the right you can feel the extra position it will have alittle catch in it. That why you need a 4 position valve otherwise the fliud will lock up in the cylinder. Hope i got that right. ....
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| MadRefereee
Join Date: Jul 2003 Posts: 23 New Hampshire
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2005-11-14 119321
This reply is long and was orignally written by a Kubota certified mechanic:
The 3 position valve and the 4 position valve, both have what is known as a regenerative circuit built into the bucket dump circuit.
When dumping a loaded bucket (with a good old fashioned loader control valve) the weight of the material in the bucket tends to pull the cylinders down faster than the hyd. Fluid can fill the other side of the bucket cylinders. Therefore, an air pocket will develop in the cylinder causing the bucket to be a little "floppy" unless held against relief for a few seconds at the end of the dump cycle. Which creates an extra step if you want to back-drag, etc.
To solve this problem we now add a regenerative (regen) circuit into the dump function of the loader control valve.
What is "regen"? The dump function of the loader control valve applies hyd. "power" to both sides of the bucket cylinders at the same time. But how the heck is that going to work? Won't the cylinder just lock up and not move? No, because on one side of the cylinder the rod itself takes up space, decreasing the volume of the cylinder, on the other side of the cylinder piston there is, no rod, creating more volume. PSI=pounds per square inch, the more volume the more square inches to apply pounds, get it? O.K. so the back side of the cylinder overcomes the front side of the cyl. due to more volume and at the same time does not allow an air pocket to develop becuase of the added resistence of "hyd. power" to the front side of the cyl. allowing the cylinder to "stay tight" for subsequent operations. And as an added bonus it tends to dump faster due to the higher amount of flow/pressure to perform this operation. (Hence the "fast dump" mode the salesmen love to tell you about) In actuality the "fast dump" mode is just derivative of the regen circuit.
Soooo..... What's the difference between 3-pos. and 4-pos. valves, besides about 35 bucks?
The 3-pos. valve has regen in the dump mode period. The problem with regen is if you want to add, say a snow plow, with power angle running off of the loader control valve, the power angle works off of single acting cylinders. With "hyd. power" being supplied to both sides of the cylinder, you will only be able to angle in one direction and that's it. (back to the whole volume-vs-psi thing again).
The 4-pos. valve has a detented position. When moving the control lever to the right, to dump (or power angle right in the case of the plow) if you choose the first detented position this is the non-regen position and will work just like the good old fashion loader control valve. If you apply a little more pressure on the control lever you will push past the detented position and move into the regen position. Thus, if you have the 4-pos. valve and want to avoid the floppy bucket syndrome you have to push full right to engage regen.
So the bottom line is; both the newer 3-pos. and 4-pos valves have the "fast dump" option. The difference is, do you want to add options to your front loader without having to add an aux valve to you're tractor or not?
....
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 | AV8R
Join Date: Oct 2003 Posts: 882 North Central Wisconsin 
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2005-11-14 119322
Nice to hear from ya, Mad. Excellent explanation. ....
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