This overview lists more than 180 parts for the Ford 8240. Electrics, lighting and trailer couplings are especially well represented in the range.
The Ford 8240 is the kind of tractor that keeps going as long as you keep up with the wear parts. This page lists more than 180 new replacement parts for it, from GRANIT, GRAMMER, MAHLE, Eaton and LUK.
If the steering feels vague or the tractor wanders on the road, look for play with the wheels on the ground. Have someone rock the steering wheel back and forth while you hold each joint in turn and feel where the knock is. When you replace a ball joint, count the turns as you unscrew it from the track rod and screw the new one on by the same amount. That keeps the toe-in close enough until it can be checked properly.
The identification plate confirms that you are working on an 8240, and the reference number on the old part is the surest way to the replacement. For ball joints and track rods, compare the taper and the thread. A joint that does not seat correctly in its taper will never tighten up, however hard you pull on the spanner.
A PTO shaft end piece with worn splines puts play into the driveshaft, and you will feel it as a clunk when the PTO engages. Replace it before the splines wear sharp and give them a light coat of grease before sliding the shaft on. A hand brake cable stretches over time and can seize in its outer sleeve. Adjust a new one so the lever has a few clicks of slack and then holds firmly, and lubricate the cable where it enters the sleeve. On the drawbar, check the pin and the rail, and replace a pin that has worn oval.
A gas strut that no longer holds the rear window open takes minutes to swap. Fit it rod down so the internal seal stays lubricated.
The Ford 5640 from the same 40 series has its own page. Look up each tractor separately, even when they share a series. You can browse the rest of the Ford range through Ford parts.