Dear Ole Mechanic;Ford 8N Tractor

I have a problem with my old 1949 Ford tractor.  I had the rear blade on it and was moving some of the dry gravel back into the ruts on my driveway.  After I was done, I was taking a short cut back to the barn when I came to a very sudden stop.  The blade was low enough to catch an eight-inch tree stump, even though I had the hydraulic control lever all the way up.  I have driven over that stump before and not gotten hung up.  I tried lowering and then raising the blade, but it still wouldn’t come up far enough to clear the stump.  I checked the level of the hydraulic oil, and it was fine--right between the FULL and ADD marks.  As I looked at things, I realized that the three-point hookup hydraulics looked like they are not going as high as they once did.  With the three- point hitch all the way up, I took a measurement from the lower link to the ground.  It was 22 inches.  Later, when I was over to a friend’s place who also has a nice 8N Ford, I had him fire it up and raise the three-point hitch.  His lower links came up to 32 inches above the ground.  Since I couldn’t remember how long it had been since I changed the hydraulic oil, I changed all five gallons of it.  It didn’t look all that bad, and I didn’t find any metal or other stuff in the old oil. 

No help, as the lower links only came up to 22 inches.  What did I break now?

Feeling Low

Dear Feeling Low;

I would bet that you are a victim of time and wear; although a crack in the hydraulic cylinder could cause your low-lift problem.  I suspect that wear in the hydraulic system manual controls has--over time--caused the lift mechanism to gradually lift less and less.  It is unlikely that the hydraulic pump has worn that much, as it sits down in the oil at all times.  It stays well lubricated; besides, a weak pump would cause slow lifting but not limit the height lifted.

The manual controls are located in the top of the housing where they only get splash lubrication.  Once the hydraulic oil gets warmed up, the rear axle ring -gear will splash oil up on the controls.  It is very hit or miss as to how much oil gets onto the manual controls.  In that linkage, there are several metal-to-metal sliding areas that can wear.   One of the most susceptible is the ne where a pin that is part of the control lever rides against a cam that is part of the lift-arm assembly.  To get to the control,s you would need to remove the top housing plate that the seat is bolted to.  If you remove the plate, be careful because there is a long arm that goes from the controls in the top part all the way down to the pump in the very bottom of the case to control the pump valves. 

Once you get the top plate upside down or mounted in a vise, you can easily see the pin and ramp and probably the worn area.  I have seen a bushing made and pressed over the pin that can take up most of the slack caused by the wear.  By the way, this is where you can also check the hydraulic cylinder for a crack.

Because of the complicated workings of the manual linkage, I will not try to cover it in this column.  Get yourself a shop manual and be prepared to pull the top housing plate more than once.  The first time I ran into this problem, I had the top plate off three different times and wound up draining and refilling the five gallons of oil twice.  Also, be prepared to either custom-machine a bushing or have a bushing made, as I am not aware of any source for a new part for your sixty-year-old tractor.  Nor am I aware of anyone that supplies rebuilt controls.  However, if you are sort of lucky, there are new hydraulic cylinders available to replace a cracked one.

Good luck.

Herr Professor Nuzanbolts