Posted by Dave in Plano, TX on Sunday, October 24, 2004 at 9:58AM :
Gentleman,
I have a question regarding the rear differential and the "allowable" backlash. My truck is a WC-12 1941 military with the stock differential and stock gearing.
I know the maintentance manual states the 0.005"-0.010" backlash is acceptable.
However, I am trying to determine if mine is OK, roughly of course, without opening up the case for a look-see.
First, I dont have a dial indicator to do this check, so why bother. And second, not sure even if I did own a dial indicator if I had the expertese to actually adjust the unit anyway.
Anyway, my first inspection, and this is all pretty much a visual examine, was of the pinion side of the rear differential where the drive shaft exits. I can rotate the pinion flange approximatly 25-33 degrees back and forth. TOTAL 25-35 degrees. There is NO slop or play side to side indicating that the pinion bearing is still in good shape.
So, can someone tell me if this amount of 25-35 degrees of rotational "free play" equates roughly to the acceptable 0.005"-0.010" limits of gear backlash? Or is this not even a close try?
If not, can someone tell me what they have for "rotationl free play" at the rear drive shaft on their truck?
Ill state here that the front diff "Rotational free play" is just about the same on my truck as the rear is.
Maybe a few degrees less, but there is still not much difference. Maybe there is supposed to be that amount of "slop"??????
Second question:
Reading the manual on this subject, it doesent seem entirly difficult to adjust all this. However, I am confused as to the procedure.
It states to loosen the bearing caps and than to adjust the bearing adjusters EQUALLY on both sides. OK. I understand all that. Thats to keep the bearings and races tensions the same. Buy doing it this way, the entire diff assembly moves either left or right, either making more or making less drive gear to pinion gear contact, untimatly altering the backlash. Am I right so far?
however, are the bearing retainer adjusters both right hand thread, or is one left hand the other right hand?
So that when I adjust, do I move both is the same physical direction (IE. clockwise or c'clockwise)?
Or does one go one way, the other side the other way?
Lastly, after the adjustment is made, is there a need to go and break the weld on the drive gear thrusst screw and adjust this to compensate for the now adjusted drive gear? See, the manual does not state this, but wouldnt this be neccessary? it staes a 0.010" clearance on the drive gear thrust screw pad to the drive gear itself. Wouldnt making backlash adjustments make this a mandatory adjustment to follow as well?
I will say I am not a mechanical idiot by any means. I know my way around a garage, but I have never worked on a differential as I dont have the tools and always have been told they are a delicate procedure and touchy to setup.
HAve any of you "back yard mechanics", like myself, ever attempted adjusting your own?
Thanks for any input on all this..
dave
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