View Full Version : Nominal checking distance on mini 8 inch diff
08-30-2005, 08:50 AM
What is the nominal checking distance (CD) on a Toyota 8 inch (mini truck) differential?
I would like to try to set one up based on the CD since I can borrow the tools to do it this way.
08-30-2005, 02:57 PM
'Bout .006" or so. Be sure to tap the carrier bearing caps as you rotate the pinion when you set their preload. I bet they loosen up out of spec after you do this...
BTW, here is a GREAT source of gear setup info for minis. You'll be reading for hours methinks... ZUK is good people.
In fact, ZUK talks about the carrier bearing rapping right here!
Methinks that issue alone is responsible for that rash of elocker failures from the Toyota factory that had mechanics doing warranty replacements for a while there. I think Toyota had a gear setup person or three who did not set up the carrier bearings correctly. In fact, that's where a couple of my elockers came from. Not to mention the busted ring gear on the Order of the Broken Ring award I made a while back...
08-30-2005, 04:00 PM
You know I'm a neophyte when it comes to setting up a diffy, but I think Stephen is talking about the distance from an imaginary point (center line of the axle if I understand the concept) to the head of the pinion. If I understand the procedure correctly the measurement is taken with a straight edge across the bearing cap thingies, without the caps on them, to the head of the pinion. By knowing the correct distance the thickness of the washer under the head of the pinion can be determined, eliminating the need for trial and error in getting the pinion depth right.
Stephen, I looked in the FSM and there is no mention of CD, besides I *think* the CD is specific to the gears being set up.
Just my 2/100th of a $, someone edumacate me if I'm off base, Brian. :confused:
08-31-2005, 06:47 PM
CHECKING DISTANCE (CD)
Should be set within about 0.002" of spec (etched on the face of the pinion gear) and is adjusted by placing shims behind the rear pinion bearing (or sometimes between the bearing race and case). Note that some manufacturers do not always machine their carrier bearing caps on exact center, but the Toyota ones I have worked on all seem to be machined on center. This helps greatly when wanting to measure checking distance, as the measurements can then be taken off the carrier bearing centerline with the bearing cap removed.
Found it here:http://www.off-road.com/toyota/gears.html
Hope it helps, Brian
09-01-2005, 07:59 AM
Duh, that's what I get for speed reading. Oh, yeah, you meant 'CHECKING distance"...:rolleyes: as opposed to backlash... :o
I have never found preset checking distance measurements helpful really, which I will use as an excuse for my sorry ignorance. I start with the last shim under the old pinion, and go from there. You would be surprised just how often it is very close, sometimes right on.
I agree, Toy thirds are amazingly consistent. That said, the mic or vernier can lie (or at least confuse), the pattern never does. www.gearinstalls.com (http://www.gearinstalls.com/) is a treasure trove of gear setup folk wisdom. ZUK's gears never fail, that's good enough for me.
09-01-2005, 08:53 AM
Thanks for the replies, guys. Yes, I want to know the checking distance mostly just to try it. True, the pattern never lies, but numbers don't either. :) I mostly just want to try it as opposed to the "pokin' and hopin'" meathod I have always used on toyota diffs.
CD was a fast way to get close and sometimes perfect with the Ford 9 inchers on the first try.
09-01-2005, 11:21 AM
Gonna use 'set up bearings' too ?
Mind if I watch over your shoulder ? I always love an opportunity to learn something new.
I have seen this done once, years ago on a D44. Unfortunately it was back in the day when I was young, inpatient and had the attention span of a gnat.
Drop me a PM, Brian.
09-02-2005, 05:29 PM
Okay, what is this "checking distance"? I've done several diffs, and at the WBPP I had the opportunity to have expert guidance (turns out I was doing it right already, but was reassured that Mike did it the same way I did). Mike and I completely rebuilt my diff with new bearings.
(1) adjusted pinion bearing preload with shims by measuring torque
(2) adjusted carrier bearing position and preload by measuring lash and by checkng pattern (which also verified proper pinion depth)
This was with FSM, which we consulted for numbers.
I have about 8k miles on this rear diff since then, no problems whatsoever.
09-06-2005, 10:54 AM
Jeff: You didn't have to mess with pinion depth because you were not changing any gears, just new bearings so you could reuse the shims(s) under the pinion head. I guess, in theory, you might have had to adjust pinion depth because of a thickness difference in the 2 bearings, but those bearing guys make their stuff pretty darn percise!
Nothing more than the distance from the centerline of the carrier bearings to the head of the pinion gear. The numbers (usually) found ground into the head are the deviation from nominal. Some manufactures have it backwards, but MOST say that -.002 means take the nominal and subtract .002 to get the pinion in the right palce. (FEW gear hobs think -.002 means there should be a GAP of .002 between the pinion head and nominal.)
The pattern doesn't lie, that is for sure, but they don't grind those numbers on there just for fun. The pattern SHOULD be perfect if you go by the numbers too.
09-06-2005, 12:16 PM
Jeff: You didn't have to mess with pinion depth because you were not changing any gears, just new bearings so you could reuse the shims(s) under the pinion head. I guess, in theory, you might have had to adjust pinion depth because of a thickness difference in the 2 bearings, but those bearing guys make their stuff pretty darn percise!Thanks for the explanation; as a matter of fact we had to assemble/dissasemble and change shim combos about 3-4 times until we had the proper inch pounds to turn the pinion, which indicates the pinion bearing preload. After we installed the carrier and adjusted it, we then checked the pattern and it was darn near perfect. I don't recall any markings whatsoever on the pinion itself. Bear in mind that this pinion was likely the original 1971 part, so maybe they didn't mark them from the factory back then.
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