Hey F.I.T. or others

The 3rd gear growl on 70D's is fairly common because that's where they did most of their work for 40+ years and the gears are probably just worn from heavy use. Kind of expensive to fix.

You COULD check the timing and high end rack setting before you pull the injectors. That can sometimes make a difference with smoking.

I don't recall if you have had those out recently, so the tips could be suspect if they are high hours. My personal view is that if you suspect the injectors, and you want to use the tractor for some real work, pull the pump and injectors, and have them rebuilt as a set. $300 and you'll know that part of the system is A-1. It really depends on how the fuel economy is, does it spritz oil on you, or does it smoke at idle. If it just smokes at high load, check the timing and rack setting, then check the injectors, then a rebuild (pumps et al), in that order.

Frank-in-Tallahassee
70D // 855

It sure sounds like bad nozzles to me, if not bad breaking pressure on the injectors (which can effectively changes timing). Bad nozzles won't let the fuel atomize, and a drop of diesel fuel will smoke like mad, where as thousands of fine droplets will burn fairly clean.

Back a page or two there was a fella that had a black smopke problem with his 730, and it turned out to be two bad nozzles.

The nozzles aren't cheap, but there's no other way to fix it if it's tips.

Frank