Glow plugs have a resistance of one ohm, higher resistance indicates trouble. The final drive issue, I wonder how badly the chains are worn from lack of lubrication. I use chainsaw bar oil in my final drives, it has the tack additive that keeps the oil on the chain as it revolves, I believe it was a gallon and a half per final drive case. I drilled a hole at the front of the final drive case at the bottom facing forward and installed a magnetic drain plug, half inch, fine thread, (use a nylon washer and silicone the plug in place between oil changes), compensate for the thickness of the metal in the bottom of the chain case and measure up to drill your hole for your new drain. Back the rear wheels up on something so that everything runs down toward the front of the loader, that way you can clean out the chain cases well, it can take a lot of scrubbing, diesel fuel might make a good solvent. It's a lot easier to change the final drive oil with the new drain plugs in the front. You might want to run some solvent or diesel fuel to clean the old Chains before you add clean oil. Adjusting the chains on the top of the chain case, loosen the three nuts on the top of the adjuster, just a little bit, loosen the lock nut, the one toward the rear of the machine a way back on the threads, slowly tighten the nut that tightens then chain, the one toward the bucket, checking the chain as you do it, it tightens up really fast. If you ever have the tops of the chain adjuster off, they say to use number two form a gasket, the stuff that never sets up completely. But the chain adjuster would fall down into the chain case so you probably don't want to do that right now. Later to check the chain tension you can use the bucket to lift the front of the loader up in the air so that all the oil goes to the back of the chain case and pull out one of the plugs under the inspection cover between the wheels, I don't remember if it was the drain plug or the level plug but then stick a steel rod in the hole and push up and down on the bottom of the chain to tell it's tightness. You don't want it overly tight, but if it's too loose you'll hear it banging on the bottom of the chain case, that's definitely too loose. If you get a service manual do not use what they tell you to adjust the chains, by rocking the front wheel back and forth when it's off the ground. When they were new you could do that, but the wear on the axles where the keys are that hold the sprockets to the axles become worn and you will over tighten the chain if you use that wheel play as described in the manual. Most of the old axles actually break a chunk out of the axle between the two 1/2 inch keys. I got new axles and sprockets years ago from Thomas. The width of the key ways was right on the money in both the axles and sprockets but there was a space on top that I had to shim so that the key would not wear and rock and try to break the key way out again. Three out of four of my original axles were broken between the key ways at 12:00 and 3:00 o'clock. The new axles had keyways at 12:00 and 5:00 o'clock I believe .The way you can tell if you got the new axles in your machine is the end of the axle in the center of the wheel is smooth, the original axles had a circular weld the diameter of the actual axle where the other piece that had the wheel studs was welded on. The chains in the final drive are number 100 chain. A 10 ft length will do one side, but the other side is longer and you have to get a few more links