First let me say thank you to all of the fine people on this board that have both asked and answered questions that have helped me get this far.
I will try to make this post short but include enough detail to get some help.
I have just acquired a David Brown 990/1 selectamatic Serial number 850726/s.
This tractor has sat for over 10 years and it has been 16 years to the date of the last oil change.
The tractor starts and runs strong but that’s about all that works. None of the lights or gauges work, etc. The clutch and PTO work great but the hydraulics are another story.
The 3 point would not do anything. So I turned to these forms and here is where I have been and where I ended up.
The transmission oil looked much like a mint milk shake. This was of course due to split shift boots. I changed them and drained the oil. When I dropped the sump all of the parts for the relief valve were torn off and left inside the filter. The top metal cap with the o-ring was bent up like it had been bouncing along the side of the road for some time. I repaired the relief valve ( spot welded it back to the lower screen and reassembled it) and replaced the filter. I filled the transmission with SAE 10W-30.
I had no oil on the right side of the tractor so I rebuilt the 3 way valve on the left side of the tractor. It was stuck and would not shift to the “L” position.
I removed the Cessna valve on the right side of the tractor the center hose coming out of the tractor case into the bottom of the valve body was broke off. I did not want to tear apart the PTO, Valve chest etc. to see if I could make it work. So I tapped the end stuck in the tractor and the peace that was in the valve body. Of course I flushed the valve by running the tractor and then changed the oil once again. Then I threaded a Stainless steel bolt into the top piece tacked it in place and faced it in the lathe then drilled a port through it. I then threaded it back into the part still in the tractor and we now have flow of oil to both sides of the tractor. Both remote hoses on the Cessna valve now have about 2,000 psi.
The 3-point still did nothing so I removed the hold valve and removed what was there. I polished the valve with 1500 grit sandpaper and cleaned everything there was not a 1/8 ball in the bottom bellow the little plate with the 3 holes in it. I put it all back together including a new ball.
I removed the By-Pass valve and it was missing the Orifice plate so I trimmed down a stainless steel shaft drilled a .020” hole in it cut off a small slice of it to make a new orifice reducer. I made a new ball retainer for the top and dropped in a new 1/8-inch ball on top. Polished the valve body and reassembled it.
Now the 3-point only works in TCU and functions what I thought was backwards. I.E you move the quadrant forward and it lifts move it back and the arms drop if you have 100 lbs plus on them.
I adjusted the connecting rod nut under the slower/faster cover. I looked under the right rockshaft cover everything in there looks to be moving correctly as you cycle through each setting. The cam appears to drop in the indent when the arms are all the way up.
At this point I removed the by-pass valve and looked at the top of the spool valve. If I place a rod on top of the stud and smack it, it definitely springs down, I cannot push it down by hand and it does not move up and down when the quadrant moves in any position. If I place a socket around the stud I can push what ever I am contacting up and down an 1/8 inch or so but it doesn’t move with the quadrant either.
So this is where I am at now. I am very hopeful someone here can point me in the right direction.
I thank you in advance for any advise you can give.
I will try to make this post short but include enough detail to get some help.
I have just acquired a David Brown 990/1 selectamatic Serial number 850726/s.
This tractor has sat for over 10 years and it has been 16 years to the date of the last oil change.
The tractor starts and runs strong but that’s about all that works. None of the lights or gauges work, etc. The clutch and PTO work great but the hydraulics are another story.
The 3 point would not do anything. So I turned to these forms and here is where I have been and where I ended up.
The transmission oil looked much like a mint milk shake. This was of course due to split shift boots. I changed them and drained the oil. When I dropped the sump all of the parts for the relief valve were torn off and left inside the filter. The top metal cap with the o-ring was bent up like it had been bouncing along the side of the road for some time. I repaired the relief valve ( spot welded it back to the lower screen and reassembled it) and replaced the filter. I filled the transmission with SAE 10W-30.
I had no oil on the right side of the tractor so I rebuilt the 3 way valve on the left side of the tractor. It was stuck and would not shift to the “L” position.
I removed the Cessna valve on the right side of the tractor the center hose coming out of the tractor case into the bottom of the valve body was broke off. I did not want to tear apart the PTO, Valve chest etc. to see if I could make it work. So I tapped the end stuck in the tractor and the peace that was in the valve body. Of course I flushed the valve by running the tractor and then changed the oil once again. Then I threaded a Stainless steel bolt into the top piece tacked it in place and faced it in the lathe then drilled a port through it. I then threaded it back into the part still in the tractor and we now have flow of oil to both sides of the tractor. Both remote hoses on the Cessna valve now have about 2,000 psi.
The 3-point still did nothing so I removed the hold valve and removed what was there. I polished the valve with 1500 grit sandpaper and cleaned everything there was not a 1/8 ball in the bottom bellow the little plate with the 3 holes in it. I put it all back together including a new ball.
I removed the By-Pass valve and it was missing the Orifice plate so I trimmed down a stainless steel shaft drilled a .020” hole in it cut off a small slice of it to make a new orifice reducer. I made a new ball retainer for the top and dropped in a new 1/8-inch ball on top. Polished the valve body and reassembled it.
Now the 3-point only works in TCU and functions what I thought was backwards. I.E you move the quadrant forward and it lifts move it back and the arms drop if you have 100 lbs plus on them.
I adjusted the connecting rod nut under the slower/faster cover. I looked under the right rockshaft cover everything in there looks to be moving correctly as you cycle through each setting. The cam appears to drop in the indent when the arms are all the way up.
At this point I removed the by-pass valve and looked at the top of the spool valve. If I place a rod on top of the stud and smack it, it definitely springs down, I cannot push it down by hand and it does not move up and down when the quadrant moves in any position. If I place a socket around the stud I can push what ever I am contacting up and down an 1/8 inch or so but it doesn’t move with the quadrant either.
So this is where I am at now. I am very hopeful someone here can point me in the right direction.
I thank you in advance for any advise you can give.