I just had some work done on my 81 Deere 450C (6505) by a local mechanic, and he tells me that "float isn't working" and he couldn't find a rebuild kit for the 6way valve. I thought he did something to break it, but when I got the unit back today, it works the way I thought it always did. This is the only dozer I've ever operated, so I have nothing to compare it to. If I elevate the blade, and move the lever to float, the blade does not fall (and the handle doesn't "sitck" in the float position), and will lower hydraulically if I hold the lever forward as if there was no such thing as float. If I lift the front end with the blade, hitting float causes the tracks to drop to earth, again, only if I hold it in float until it drains. Is this the way it's supposed to work? I guess I'm comparing it to float on my 580E, which "latches" in float position. Should it latch? I haven't tried this, but I'm guessing if I float the blade, then drive over uneven ground, the blade will lose the ground reference (unless I maintain pressure on the lever). Again, the 580E just keeps the blade on the ground.
Any "float" I have ever know is supposed to keep the bucket/blade, etc, "Free Floating" along the surface being graded/ excavated. It is supposed to lock when pushed all the way past the down pressure position on the lever. It opens the valve to allow the cylinders to travel freely without any hydraulic pressure up or down... In other words it creates an open circuit for the hyd oil. in and out and too and from the cylinders. No pressure involved. If the float worked right when the dozer is lifted up by the blade and you shove the lever into "float" it would lock in float anf fall to the ground very quickly and if you got off the machine and used a loader to pick up the blade it would offer no resistance at all other than the weight of the blade.
That's what I would expect, at least based on my 580E. Can someone confirm that a Deere 450C should act similarly?
I can confirm my 650J and a 750 that I have operated behaves the way Tim T described.
Every 450C I ever ran had a control valve would "latch" in the float position and allow the blade to move freely up and down. With the blade all the way up it should drop very quickly to the ground and stay in the float position.
I can attest the parts lines for the 450A/B/C are drying up at Deere. Friend of mine had one and since moved up to a 943 Cat as there were pieces we needed that our supplier had to scrounge out of NOS at other dealers to acquire. He got rattled and traded out.
I have a straight 550JD with a 6 way that indeed floats in the detent past hydraulic down pressure.
Your 450C control lever should indeed stay in the float position. If you have always operated it as it is with no undo hardship I would continue as you always have and not worry about it. No sense chasing used parts that are probably in the same shape as the one you have. If you ever did need float such as in snowplowing a long ice road you could use a bungee cord to hold the lever in the float position.
I DO have a 1975 450C w six way blade.... It works as I described. As far as being critical to me... float is not that important. I seldom use it even if back blading. I just use the down pressure according to ground conditions. As far as parts.. I have had no issues, they built a huge amount of those machines... tons of parts machines available and most JD construction dealers can get all the parts you need..at a price. JD is right next to Cat as far as support for old machines... Heck we had a 1953 40C and never had much trouble getting new or used parts. Try Ebay or.... Go to http://www.jdcrawlers.com/messageboard/index.php they will have tons of parts places and fixes. New and used. Lavoy Wilcox who runs the site is a used JD parts dealer himself.
Float detent isn't working. Spring broken or the sleeve is worn out
I solved my float problem. My mechanic claimed the endcap of the tilt valve had fallen off spewing parts all over. He had showed me something he thought was a broken part. The mechanic was wrong about which valve. It turns out, the detent plug had backed out, spewing the spring washers and other parts onto the compartment floor. The broken bits he had found (and thrown away) were the needed part, still in perfect condition. I repaired it by bending a piece of 1/8" brass welding rod into a 3/4" ID spiral, cutting one turn into four pieces. The ring pieces get squeezed between two contoured washers (thinner one on top) by a pile of spring washers. Adjusting the plug on the bottom of the end piece ("detent") adjusts the grabiness of the float position. Not hard to assemble if you stick your finger into the small end to contain the pieces.