TO-20 Hydraulics

Thanks

Get some CLEAN containers suitable for oil collection that will fit under the transmission housing of the tractor. Remove the THREE drain plugs, one under gearbox, large plug under hydraulic pump, and small plug under rear axle. Allow the oil to drain completely from the system, its better if the oil is warm before you do this.
Remove both round side inspection covers from the centre axle housing directly below the seat.
Remove the four screws from around the PTO shaft housing and pull the PTO shaft out of the tractor, this is about 30” long, Through the side covers, follow the control fork downwards to the bottom of the housing and spread the fork legs to allow the control valve crosspiece to clear the fork legs. You can assist this procedure by working through the drain plughole in the bottom of the pump if required. (On later tractors 1953 onwards, a bridge piece was fitted between the fork legs to stop them twisting and allowing the crosspiece on the control valve to come adrift, if you have one fitted with this bridge, its sufficient to remove a screw from just one leg of the fork)
If you have any extra pipe work fitted to the Hydraulic pump housing, remove it, then undo all the setscrews holding the pump into the bottom of the centre axle housing, lower the pump out of the housing. If the pump sticks in the housing, gently pry it out at the corners where there is a tapping, do not use any force or you may damage the pump body. Refitting is reverse of the above, use all new gaskets, making sure that all of the old gasket is completely removed, no gasket cement is required or necessary or desirable on any gaskets on the hydraulic system.

Do not use the old oil if it is in any way contaminated with condensation or sludge.

Hydraulic oil…should be changed every 720hours. or every 12 months whichever comes first. This is due to there being no filter fitted and possible contamination entering the system from outside sources i.e. diggers/loaders/trailers and also due to condensation taking place in the housings. Oil required for refill is a straight mineral oil, not a detergent type, SAE40 in UK or in USA and Canada, a 90 weight oil above 50°F or 80 weight below 50°F Total capacity is 5 imperial gallons in UK or 24 quarts in USA

Remove the seat assy. from the lift cover, clean the area thoroughly so no dirt or dust will fall into the system housing. Remove both round side covers from the centre axle housing, for your convenience make sure that you have the PTO in gear before you remove the lever. You will need something to catch the excess oil that will come out of the inspection holes, when you remove the covers replace the bottom setscrew in each side to limit the amount of oil that will be lost.
Through the inspection hole, follow the long control fork down into the oil, at the bottom is the control valve, this needs to be disengaged from the fork by spreading the fork slightly so the crosspiece of the valve will come out of the fork. On tractors built in 1953 and later, there was a bridge piece fitted between the legs of the control fork just above the oil level to prevent the control valve becoming detached, if this is fitted it will need to be separated from the fork (remove screw on one side only will do) to allow the fork legs to spread. If you find it difficult to spread the fork and remove the cross-piece on the control valve, it will help if you drain all the oil from the system (about 5 imp. galls or 24 US quarts from 3 drain holes, i.e. gearbox, hydraulics, rear axle) and get at the valve through the drain hole in the hydraulic pump, but usually you can manage without that. Once the valve is free of the linkage you can now concentrate on removing the lift cover itself. Detach the trunnion on the main control spring from the top link rocker.
Remove the pins from the lift-rods on the cross-shaft lift arms.
Remove all the setscrews from the outer edge of the lift cover (do not touch the 4 bolts in the middle as these hold the ram cylinder in place)
Using a lever under the cross-shaft on the axle housing, pry the cover gently loose, then lift the cover straight up carefully, so as not to catch anything. (it requires 2 people to do this, don’t attempt it on your own) lift the whole thing clear of the tractor and lie it on its back, just be careful that you don’t catch the control fork and damage it. You can now get at the ram cylinder and all related parts, if you are changing the gaskets on the ram cylinder, remember that there are THREE gaskets. one large one at the front and one on each of the rear bolts to level it up. If you are replacing any gaskets, make sure you thoroughly clean all the old gasket from the housing, otherwise you may get leakage under pressure. No gasket cement is required or necessary or desirable on any of the gaskets.

Refitting is the reverse of all the above, just take extreme care when lowering the lift cover into place on the tractor and that you don’t damage the control fork or control valve.

Hydraulic oil…should be changed every 720hours. Or every 12 months whichever comes first. This is due to there being no filter fitted and possible contamination entering the system from outside sources i.e diggers/loaders/trailers and also due to condensation taking place in the housings
Oil required for refill is a straight mineral oil, not a detergent type, SAE40 in UK or in USA and Canada 90 weight above 50°F or 80 weight below 50°F Total capacity is 5 imperial gallons in UK or 24 quarts in USA.

The system pressure should be 2050PSI.

To check the pressure properly you need a pressure gauge coupled to either a trailer pipe connection or into one of the tapping points on either the lift cover or Hydraulic Pump assy. The linkage arms need to be held from going to the top of the lift stroke, by either using a trailer Pick-up Tee bar (ideal) or some strong stay bars used with the drawbar (standard ones are NOT strong enough) and they should NOT be coupled to the top link connection on the tractor. When you have all this in place, move the fingertip control lever to the lift position and check the reading on the gauge, should the reading be low. (i.e. by more than 200psi) then you can assume that there is a leak in the system and that it isn’t just the relief valve (also called safety valve) blowing off or even leaking due to wear. At this point I will warn you DO NOT PUT YOUR HANDS INTO THE HOUSING WHEN THE ENGINE IS RUNNING
Check the main control spring, (under the seat) for end play, there should be no end play at all but you should be able to turn it with an implement mounted and in the raised position, if there is any end play this will have to be removed, as this alters the control valve linkage internally. The Hydraulic lever quadrant should also be checked that it is set correctly, again with the implement raised, move the lever slowly forward till the implement starts to drop, then move the lever slowly rearwards till the implement neither lifts nor lowers, at this point the front of the lever should be 2 ¼” on TE20 or 2 ½” on TO20/30, to adjust this setting, slacken the 4 bolts that secure the lever to the lift cover and move the quadrant slightly till you get it right. Make sure that the control spring is set correctly first though otherwise you will only make matters worse by trying to set the quadrant first.

Remove one or both of the round inspection covers on the centre axle housing which contains the hydraulic system, Run the engine with the PTO and Hydraulic Pump in gear, with either the rear linkage fastened down as previously or with an implement mounted in the normal way, lift the rear linkage and look inside the inspection cover using some light so you can see inside the top of the housing, you will see the hydraulic lift ram cylinder right above the inspection holes, there should be little or no leakage from the rear end of this. If leakage is occurring, it can be a damaged piston or worn piston rings, the leakage rate should not be a constant flow, but drips are ok. If there is no leakage from the rear of the ram cylinder, now check the front of the cylinder, if there is a leak here it can be either a cracked cylinder or possibly just the gaskets under the cylinder. If this is the case the Hydraulic lift cover will need to be removed to replace the gaskets (see separate sheet for instruction on this) If there are no leaks in the top around the ram cylinder then check the front right hand corner of the lift cover inside the housing to see if there are any leaks in this area (this is where the pressure from the pump is fed into the lift cover) it is possible that it could have blown the main gasket under the lift cover due to the bolts being incorrectly tightened or not being checked for tightness occasionally. (From TE20 serial number 330,043 (1953) the hydraulic relief valve was moved to this position, you can check this externally by looking if it has a large square bolt head at this point or the original small plug with the recessed hole for an Allen key). If there are no leaks in the top at all then the leak must be in the bottom of the housing in the area of the Hydraulic pump

With the linkage still in the raised position and with the engine running, check in the bottom. Of the housing for the oil swirling around (there will be movement of the oil because the pump is running but that will only be slight) check for the swirling of the oil and that is where the leak is occurring. If it is at the front right hand side it could be simply be that the gasket under the pump has blow at the point where the pressure leaves the pump to go to the lift cover, again this is usually due to the bolts not being sufficiently tight.
(To remove the hydraulic pump, see the separate sheet)
If the swirling is towards the rear of the housing and maybe only on one side then it could be a side chamber gasket leaking, but usually you will find that the hydraulics lift in a jerking fashion (due to pressure from one or more cylinders not being available due to the leak) If this is the case, you will have to remove the hydraulic pump to effect a repair.

Thank you for your help!

mikeunderwood78@hotmail.com

I would be extreamly greatful.

Cheers
mike