I was happy to see a "Forestry" category. My family has been in the forestry/timber industry since the depression days. My grandpa started his own sawmill operation in 1947 which employed all of my family except me for years. I am actually a machinist now. They all still do it but branched off somewhat.
My younger brother is a logger in South Central Missouri. He has a 540 John Deere skidder and he just bought a John Deere 640 with a grapple. The problem is a couple of the most needed gears don't work properly,(hydrostatic transmission). The person he got it from said it worked perfectly when he bought it. He drained the fluid to fix a leak and replaced it with new fluid and that is when he lost those certain gears. The person he got it from is a very trusted friend so no questions about what he said. He said he tested the fluid pressures and found one of the pumps wasn't pumping enough pressure. He told my brother that the pump would need replaced.
My question is, is there something which could have been put in the fluid to "hide" that problem so that it wasn't evident when my brothers friend bought it or does anyone feel that something else other than the pump my be the problem. I was thinking it might be a blockage somewhere or something to that effect. I didn't think you could do much with hydraulics to hide something(like sawdust to quiet noisy gears).
Also, is there an easier way to replace it without completely removing the engine. How hard is it to rebuild those pumps. I looked at an extra pump he has and I not 100% certain how it works. I am thinking that it must increase the pressure as it goes thru another"piston" and then progressively on thru the rest of them. I believe it has 8 small "pistons" around it's circumference and a "cam" in the middle. I think a lot of the JD tractors have a similar if not the same pump.
Thanks in advance
Tim
My younger brother is a logger in South Central Missouri. He has a 540 John Deere skidder and he just bought a John Deere 640 with a grapple. The problem is a couple of the most needed gears don't work properly,(hydrostatic transmission). The person he got it from said it worked perfectly when he bought it. He drained the fluid to fix a leak and replaced it with new fluid and that is when he lost those certain gears. The person he got it from is a very trusted friend so no questions about what he said. He said he tested the fluid pressures and found one of the pumps wasn't pumping enough pressure. He told my brother that the pump would need replaced.
My question is, is there something which could have been put in the fluid to "hide" that problem so that it wasn't evident when my brothers friend bought it or does anyone feel that something else other than the pump my be the problem. I was thinking it might be a blockage somewhere or something to that effect. I didn't think you could do much with hydraulics to hide something(like sawdust to quiet noisy gears).
Also, is there an easier way to replace it without completely removing the engine. How hard is it to rebuild those pumps. I looked at an extra pump he has and I not 100% certain how it works. I am thinking that it must increase the pressure as it goes thru another"piston" and then progressively on thru the rest of them. I believe it has 8 small "pistons" around it's circumference and a "cam" in the middle. I think a lot of the JD tractors have a similar if not the same pump.
Thanks in advance
Tim
