[Fot] differential Pinion Height

Sun Aug 30 07:27:03 MDT 2015

thanks, guys.  Between Glen, Bill and Jim, I know what to do.  The factory manual instructions must be some truncated version of what they used, having specific jigs and manufacturing directions.

On Aug 29, 2015, at 10:17 PM, Bill Babcock wrote:

That’s pretty slick, but it doesn’t set the pinion height. The pinion height above the bearing determines where the teeth contact the drive gear. The lash from the shims on the right and left side of the spider determine the depth of engagement, but pinon height determines the point of engagement—either at the base of the driven gear, the middle (where it’s supposed to be) or the top. Unfortunately, lacking the factory gear bobs and gimcracks, the only way I know to do this is to guess, then install everything, paint the gear teeth with blue, and roll them through an engagement cycle. The pattern on the teeth tell you where you are. then take everything apart again, change stuff, and try again. Last time (two weeks ago) took me five tries to get it right, but that’s better than the first time I did it. I can now fix two things at once (height and depth), and I’ve learned to go in tiny increments (.003” or less if you have a skinnier shim—the smallest from moss are .003” but my stash has some .001” in it of both the spider shims and the pinion shims. I don’t worry too much about the bearing preload for either the pinion or the spider. I figure if I don’t have shake in the pinion and can just barely get the diff out, then I’m in the ballpark. I’m not trying to build a 50K mile, noiseless diff, I just want it to hold together in races and not be louder than my singing when I’m racing (yes, I do). 

> On Aug 29, 2015, at 3:42 PM, James J Dolan <jdolan at voyagerhldgs.com> wrote:
> 
> Wow
> Imagine building Triumphs on an assembly line and doing a few hundred rear axles a day that way. 
> 
> A Guinness or two at lunch and the next thing the whole contraption falls over and the lead shot goes everywhere, and the poor bloke spends the entire work shift picking up tiny marbles. Quality control problem!!
> 
> Sure explains why the damn cars stopped being made and the British no longer have an Empire. 
> 
> And to think we race them......
> 
> All joking aside, that is pretty creative. 
> 
> Jim
> 
> GT6 #6 Kastner
> GT6 #4 Group 44
> GT6 #5
> 
> Sent from my iPhone
> 
> On Aug 29, 2015, at 4:13 PM, J.C. Hassall <jhassall at gmail.com> wrote:
> 
> Scott,
> 
> This is how I set up my TR4 pinion.  A 1/2" square piece of steel stock inserted into a socket.  The steel bar thru the square stock was counter balanced to give zero rotation.  With inch increments lightly notched into the rod, it was easy to locate the bag of lead shot at precise locations.  When the rod tipped, the pinion torque was dead on.  BTW, the 2x4 was supporting the diff front, not the drive flange.  It only took a few trials to tighten the nut to the required torque.
> 
> hth
> 
> jim
> 
> <pinion preload tool.JPG>
> 
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> <pinion preload tool.JPG>
> 
> On Sat, Aug 29, 2015 at 2:54 PM, Scott Janzen <sjanzen at me.com> wrote:
> I'm replacing the bearings in the diff (w/Timken USA) and am puzzled by the "set pinion height" instructions.  Here's what the workshop manual says (paraphrase):
>  - install the pinion head bearing without the normal 0.10" spacer between it and the pinion.
> - install the pinion shaft with bearings, no bearing spacer, shims or oil seal, and torque to 12-16 ft-lb
> - put a dial gauge on the housing with the plunger contacting the pinion, then putting downward pressure on the gauge, obtain a maximum reading  (appears to be one of those special factory tools in the photo though none is cited)
> -this reading, subtracted from the normal spacer thickness of 0.10", determines the thickness of the "selective spacer required".
> 
> Huh?  first of all, the spacer is 0.10" so how can there be a different thickness spacer?  The diagram shows no shims at this location.  Second and more important, why would the assembly move at all and produce any dial indicator readings, given that the pinion bearing assembly is torqued to 12-16 lb?  
> 
> These are not the instructions for shimming the spacer between the bearings, I understand those - though I am looking for ideas for a homemade preload gauge I could easily make up.
> 
> Are the instructions missing something or am I?
> 
> thanks!
> 
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Bill Babcock
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