Wear on clutch/brake pedals & hole in drawbar indicate amount of use. Speed hour meters(tachometer) have been known to quit and been changed out.Condition of oils & coolant very important. I'd use a test kit especially for coolant. Check operation of trans,hyd system & brakes.
One of the most common problems with the old syncro ranges is the shifter itself. I suggest that you check the shifter quadrant closely for the amount of wear/play within the gates. Shift it through all the gears and make sure it will go and stay in ever gear.
The shift pattern should be fairly smooth (you shouldn't have to look for the gears) and the shift lever should be fairly tight when in gear (no flopping around). If you have problems getting it in gear or it staying in a gear, I would be cautious as this could be anything from a simple lever adjustment, worn gates or a broken synchronizer in the trans.
Old style, 70's model, and I was wrong about the tranny. It's a power shift tractor. From the owner, problems are: Small amount of blow by, 1 remote leaks, 1 battery box rusted, valve cover gasket leaks. Runs great, shifts tight, strong lift, good pto, sheet metal great. This is all from the seller's point of view. Headed up to check it out tomorrow, more to follow.
Powershift tractors are very durable(hard to tear up) but are very expensive to repair. You need to check trans through all 8 forward & 4 reverse gears. FYI older 4020's were built from '64-'68 and later models(side console) from '69-'72.
decided to pass on the 4020, as it was a little worse than expected. Most of it's issues were minor except for the blow by, which wasn't so bad as to need an overhaul immediately, but it would eventually. Main reason was he wouldn't come off the price enough to make me comfortable with the repairs needed.