Re: D300 Output Shaft Endplay Measurement Problem
To answer your two questions.
1) what is the correct way to measure end play? In/out or Side/side?
Ans. In/Out, exactly as you have shown in your picture.
2. In the directions (Tera's)it says to measure said endplay with not more than 10inch pounds of preload. Does that mean tighten the yoke nut to that spec and then measure?
Ans. The reference to 10inch pounds of preload is a separate type of measurement. So, first assemble the output shaft and tighten the yoke nut to the required 120 ft-lbs and measure the end play with the dial gauge. Then remove your dial gauge and with an inch-pound torque wrench, preferably a dial type, if you have one, measure the bearing drag or preload. This is a measure of the amount of resistance the bearings have as the shaft is slowely turned.
One thing to note, the factory manual I have makes no mension of measuring the preload with an inch-lb torque wrench, they only specify end play (0.001 - 0.005). I suspect the measurement of rotating torque is a "double check" type of measurement to ensure there is no binding of the bearings. I would also try to keep the end play within spec but on the tight end of the range, nearer to 0.001 then to 0.005
Another thing I've seen for those of you who can't afford a good dial type of inch-lb torque wrench is a trick I had seen in one of the old MOTOR manuals for trucks. In that book they showed a cylinder, something like a tin can attached to the end of the shaft, and a string and a small spring scale, like you would use to weigh a small fish. The string gets wrapped around the tin can and the end is pulled with the spring scale as the string unwraps from the tin can. A little math gives you the rotating force in inch-lbs. If your tin can were 4 inchs across and scale measured 10 lbs then the force measured would be 2in*10lbs = 20 in-lbs. I haven't tried this myself as I spent the money on a good inch-lb torqe wrench.