Check all the fluids for signs...
Check all the fluids for signs of trouble. Obviously water in the oil, oil in the coolant, and major oil and fuel leaks are bad. Also check the radiator for cracks and leaks.
Drivetrain And Chassis
There are a few engines that were used in the M35A2s. As with any engine, inspect it for major oil or fuel leaks. Also check the radiator mounts. If they come loose the radiator can crack and leak at the inlet and outlet bungs.
The most desirable of all of the available diesels is the LDT-465-1C "whistler" turbo. It's easily recognized when running. The turbo features an extremely audible whistle. Typically there is also a tag on the front of the engine with the designation if there is any doubt. Some LDT-465-1C diesels even have a multifuel option. This allows the truck to run on gas, jet fuel, kerosene, diesel, or any combination of these fuels. Since it's an older non-computerized diesel it's also the perfect candidate for B100 biodiesel or even vegetable oil with the proper cold-weather tank-heating equipment.
The M35A2 has a 24-volt electrical...
The M35A2 has a 24-volt electrical system that is made up of two 12-volt batteries. Missing battery caps and leaky batteries make a mess of the metal battery box. It's best to eventually convert over to two 12-volt dry-cell batteries.
All but the earliest M35A2s came with the bombproof Spicer 3053A Five-speed manual transmission. It's only real disadvantage is the oddball shift pattern. You'll get used to it. But look for a truck with the air-shift Timken T136-27 transfer case. It's easy to spot; the truck will have an air-shift lever just below the center of the dashboard. This is a far superior unit compared to the Timken T136-21 sprag-type transfer case. Although the sprag T-case can be outfitted with an aftermarket REB kit from Memphis Equipment to make it more reliable.
The axles feature air-assist drum brakes all around. Greasy driveshaft U-joints are a good sign. It at least means someone knows where the grease fittings are and uses them. The most wear-prone items in the axles are the pinion bearings. You can check these by releasing all tension from the drivetrain. First release the E-brake and put the tranny in Neutral. Then have a buddy keep the truck in place with the brake pedal. Grab each of the six pinion yokes and check them for endplay. They should be tight with zero slop. While you are under there, inspect the rubber bushings on both ends of the six rear torque rods (two uppers and four lowers). A few small cracks in the bushings are normal but rotten and missing chunks of rubber are bad signs. They may need to be replaced. The parts are available and relatively inexpensive but it's not an easy task. While you are checking the pinion yokes on the front axle make sure the knuckle boots are in good shape and not torn or missing. Also inspect the tie rod for bends and the tie-rod ends for wear.