I'd bet that is what happened. Again the time frame would be about right. The tractor was ordered  in early 73. I can at least write down the serial # so when I order parts the parts guy doesn't look at me like I've lost my mind. <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) --> Thanks for the effort. If I ever get to the point where I'm rich and famous, I'll buy a set of 26 inch wheels and switch to the 14.9 X 26 tires. With the 16.9 X 24's the lead is about 0, maybe a tad of lag but not much. I can live with that for now. One thing you can say for the 310 engine is that they sure do perform in the field. And they are pretty good on acres worked per gallon of fuel. The first 310 we sold was a 1950T 2WD and we put it up against a 4320 JD on a JD 38 forage harvester. The guys farm was a frog pond, basically. We made the pass down the field, up the other side down again and 1/3 of the way up the far side before we had the badger tandem wagon full enough we couldn't pull it any further. After he bought the 1950T he told me the 4320 only got up the far side about halfway the first time around before he got stuck. This farmer had really nice corn and I was still running in second direct and second over (mostly second over). I could run the throat on that 38 all the way open before the motor even started to come unto the governor. A couple of years later we sold the gent a 1955 4WD. When I was doing custom tillage I would pull a 12 foot Oliver disc and a 12 foot Oliver field cultivator behind the disc. Used 3rd and 4th gear depending on the soil I was working in. Ten front end weights seemed to be about right to hold the front end down to pull properly with that draft load in our steep hilly terrain.  One pass and the field was ready to plant.