I second Andy's question. Will some gear experts PLEASE!!! come forward and tell us how to set the gear mesh?
I just reviewed my "Dudley" gear handbook while eating lunch and it reminded me of many things.
All this folk lore about can/t use steel with iron, bronze must be used with steel is an old wifes tale. Steel can be used with steel, iron or bronze; just the correct tolerances/lubes must be applied.
For the touters of can't use steel on steel; think for a minute what your rear ring and pinion are made off? What about the transmission, ie, all hardened steel on steel.
The distributor gear is hypoid or cross helical and are very sensitive to base circle matching. Scanning the tables of tolerances in base circle and backlash they are in the range of .001 to .005 in.
I recall reading about a yr ago that you had to set and shim the depth of the distri. engagement to less than .010 in. tolerance. I can't find that tech article anywhere. Someone have it? This squares with everthing in the handbook.
What I think is happening is that all the manufactures are machining with a -o/ +oox toleracnce so that there parts won't be too "short". Both the distributor people and the block both take this "proper" tolerancing strategy. The problem occures when both are at the +.005 x 2 and you get a +.010 in "too deep" mesh. When the base circles are off by this amount the tooth tip can't clear the base cirlce and it quickly machines the clearance itself. This self machining distroys the surface smoothness and rapid wear insues. This is probably happening much more frequently because of the frequent use of different manufacture's products; detroit blocks, mallery, MSD, Ford disti, etc. The chance of being off .005 to .010 in is greatly increased
This problem is analgous to setting up ring and pinions. I have tech manuals that show how you dial indicator it close; then put "dycom blue"? on the gears and run them for 15 minutes and then inspect the contact pattern. It even shows pictures of the contact patchs and the resulting shims need to bring the contact patch to the center of the pitch circle. The cam/distributor gears sensitivity and setup needs the same care and careful control of the tooth/engagement depth.
I'm about 80% sure that proper shimming under the distri. housing to insure the proper depth will correct the rash of gear failures. Can somefind those/articles or know the " correct-measure-shim" procedures please inlighten the masses. For all those that are eating gears ever 500 mi, a fifth would be appropriate for a fix.
grover niles
gears
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