Harold (and others?),
My TR4 differential's pinion to crown gear 'backlash' is in the range of
0.000" to 0.007". Factory is 0.004 to 0.006 so yes at 0.000 (in only one
spot), and no lube, absolutely no play and a little hitching (but when it's
lubed, gears spin very easily). At two other spots in the gear meshing
backlash is 0.007 so it gets a little sloppy as well. Prior to the
rearrangement of shims the backlash was a huge 0.025" overall! Now MOSTLY the
backlash seems to fall between factory specs 0.04-0.06". I think the pinion
was moving in and out of mesh slightly after my oil seal change 20 years ago
- at that time I didn't torque the input flange bolt so that (in my
imagination) the pinion could float a bit toward the crown and close up loose
backlash! (yeesh) Now I'm thinking the pinion kind of floated back and forth
some thousandths and over the years created a slight varying pattern in my
gear teeth? But I don't recall hearing any rear-end whine over the usual roar
of everything else. With the backlash now set closer to specs, and using
engineering blue, the heal/toe contacts on teeth seems right on and wear on
teeth surfaces seems slight - they're smooth as glass.
My dubious question is - can I use lapping compound to relieve that one tight
spot (no backlash) between pinion and crown tooth and have a decent quiet
diferential with varying backlash of say between 0.003 to 0.007 instead of
0.004 to 0.006?
Carl
'63 TR4 since '74
------------
As someone else stated, ring and pinion gears can be mixed but will be noisy.
This is because after the gears are cut, they are mounted on a machine that
runs the gears then lapping compound is applied. This takes off the high
spots and matches the surfaces of the ring and pinion.
EP (Extreme Pressure) gear lube functions by leaving a solid coating of
sulfur ( or other additive) on the wearing portions of the gear. This solid
film is what lubricates the gears.
Harold
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