The Naa hydraulic control adjustment procedure involves setting the draft control spring tension and the position control linkage so the three-point hitch responds correctly to load and height. This is done by loosening the locknuts on the control rods and turning the adjusting nuts, then checking the hitch’s behavior with the engine running.
Background: The NAA Hydraulic System
The Ford NAA (also called the Golden Jubilee) was introduced in 1953 to replace the 8N. It used a new hydraulic system with both draft and position control, a major advance over the 8N’s simpler system. The NAA’s hydraulics are driven by a gear pump inside the rear axle, delivering about 2,000 psi. The system operates the three-point hitch and can also power a remote cylinder through the auxiliary ports.
Draft control lets the hitch respond to how hard the implement is pulling, raising or lowering it to maintain consistent depth. Position control moves the hitch to a set height and holds it there. These two functions use separate linkages inside the control box, and both need periodic adjustment to keep the hitch working properly.
How the Adjustment Works
The adjustment is done on the control box, which sits on the top of the rear axle, just behind the seat. There are two main adjustments: the draft control spring and the position control cam. The draft spring is a heavy coil spring that compresses when the implement pulls against the top link. The position cam is a curved plate that moves with the lift arms.
The procedure is basically the same for both: loosen the locknut, turn the adjusting nut to change the linkage length, then retighten. The goal is to get the internal valve spool to move the right amount at the right time. If the linkage is too long or too short, the hitch will overreact, underreact, or not move at all.
Here is the general step-by-step for the draft control adjustment:
- Park the tractor on level ground and set the brakes. Shut off the engine.
- Remove the cover from the control box (the round cover behind the seat).
- Locate the draft control adjusting nut on the rod that connects the top link to the spring. It is usually a 9/16-inch nut.
- Loosen the locknut, then turn the adjusting nut to lengthen or shorten the rod. Turning it clockwise (as viewed from the rear) increases spring tension.
- Retighten the locknut and replace the cover.
- Start the engine and test the hitch. With the draft control lever in the lowest position, the hitch should stay down. As you raise the lever, the hitch should lift smoothly.
For the position control, the adjusting nut is on the rod that connects the lift arm cam to the control valve. The procedure is the same, but you are setting the point at which the valve returns to neutral when the arms reach the selected height.
How to Choose the Right Settings
There is no one-size-fits-all setting. It depends on the implement and the job. For heavy tillage tools like moldboard plows, you want the draft control to be sensitive so it responds quickly to changes in soil resistance. For light tools like a finish mower, you want the draft control almost off, and use position control to hold the mower at a set height.
Start with the factory recommended settings, then fine-tune from there. The Ford service manual gives a starting point of about 1/8-inch clearance between the adjusting nut and the spring retainer. But you will need to adjust from that base to get the behavior you want.
Here are some general guidelines:
- For plowing or other draft work: set the draft spring so the hitch starts to raise when the implement meets moderate resistance. You want it to respond quickly but not so fast that it bounces.
- For mowing or light work: set the draft spring loose (less tension) so the hitch stays put, and use position control to set the height.
- If the hitch drifts down while in position control, increase the friction on the position control lever (there is a separate adjustment for that) or check for internal leakage.
Common Problems and Misconceptions
A common misconception is that the NAA hydraulic adjustment is only about the draft spring. In fact, the position control linkage is equally important. If the position control is out of adjustment, the hitch may not return to the same height each time, or it may drift down when the engine is off.
Another common issue is that the hitch drops when the engine is shut off. That is normal on the NAA because the hydraulic pump stops, and the fluid drains back. It is not a sign of a problem unless it drops while the engine is running.
If the hitch is slow to lift, the problem is often not the adjustment but the hydraulic pump or a worn valve. Check the fluid level first, then look for leaks. If the fluid is foamy, there may be air in the system, which can cause erratic behavior.
Comparison with Other Ford Tractors
The NAA’s system is similar to the later Ford 600 and 800 series, but there are differences. The 600 and 800 have a different control box and a slightly different linkage. The basic adjustment procedure is the same, but the part numbers and some dimensions differ.
The 8N, which came before the NAA, had only position control, not draft control. So the NAA is a significant upgrade. If you are used to an 8N, you will find the NAA’s hydraulic system much more versatile, but also more complex to adjust.
Costs and Parts
Adjusting the NAA hydraulics is free if you do it yourself, but you may need to buy a few tools. The adjusting nuts are standard hardware, but you might want a new locknut if the threads are worn. The control box cover gasket is a common replacement item, costing about $10.
If the hydraulic system has deeper problems, such as a worn pump or valve, you are looking at more significant costs. A rebuilt hydraulic pump for the NAA costs around $200–$300. A full control valve rebuild kit is about $50–$100. Labor, if you have a shop do it, will add another $100–$200.
It is worth checking the adjustment first before assuming you need expensive parts. Many owners have fixed a sluggish hitch by simply adjusting the linkage and cleaning the control valve.
Safety and Best Practices
When working on the NAA hydraulic system, always lower the hitch to the ground and shut off the engine before removing the control box cover. The hydraulic fluid can be hot, and the system holds pressure even with the engine off. Relieve the pressure by moving the control lever back and forth a few times with the engine off.
Use clean hydraulic fluid, and check the level with the dipstick on the fill cap. The NAA uses Ford 134 fluid or an equivalent. Do not mix different types of fluid, as that can cause foaming and poor performance.
When testing the hitch after adjustment, keep your hands and feet clear of the lift arms and any attached implement. The hitch can raise quickly and with enough force to cause injury.
Frequently Asked Questions
How do I know if my NAA draft control is out of adjustment? The most common symptom is that the hitch bounces or surges when pulling an implement. It may also fail to raise the implement when you move the lever, or it may raise too high and then drop back down.
Can I adjust the NAA hydraulics without removing the control box? Yes, the adjusting nuts are accessible through the top cover. You do not need to remove the entire control box. Just remove the round cover behind the seat.
What is the difference between draft and position control on the NAA? Draft control responds to the pull on the top link, raising or lowering the hitch to maintain constant depth. Position control moves the hitch to a set height and holds it there, regardless of load.
Why does my NAA hitch drop when I shut off the engine? That is normal. The hydraulic pump stops, and the fluid drains back to the sump, allowing the hitch to lower. If it drops while the engine is running, that indicates a leak in the lift cylinder or control valve.
What fluid should I use in the NAA hydraulic system? Use a quality hydraulic/transmission fluid that meets Ford specification M2C134A. Many aftermarket fluids are available, such as those labeled for Ford 134 or equivalent.
Template: NAA Hydraulic Adjustment Record
| Date | Adjustment Type | Setting (turns from full in) | Notes |
|---|---|---|---|
Sample (fictional): Date: 2025-04-10; Adjustment Type: Draft; Setting: 1/8 inch clearance; Notes: Set for plowing, works well.