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Old 10-02-2005, 11:51 PM
leiniesred leiniesred is offline
Hard Core 4+
Join Date: Aug 2005
Location: Aurora, CO, USA
Posts: 1,298
Default I built a turbo into my differential

Yeah right, but anyway, at 2100 to 2200 RPM at the input shaft of my rear diff, I hear a turbine frequency gear whine. Not a howl, but a wine and at a very limited RPM range. The gears have about 60 miles on them so far.

The background: I put together my 5.29 ARB V6 differential using yukon gears. The pattern looks great. (sorry, no pics) Anyway the pattern is centered tip to root and covers about 80% of the drive and coast sides with a slight concentration on some, but not all teeth toward the toe on the drive side. The coast side shows a cocentrations a litte to the heal. The pattern is too centered heal/toe to be called "competition" pattern.

Their seems to be more pattern variation from tooth to tooth than I have seen on some other gearsset I have built. Maybe these are the "economy" yukons?

I can keep my hand on the axle housing after a 15+ mile run at about 45 MPH. It is hot for sure, but not TOO hot.

I was concerned about the noise and the heat so I took it all apart today. Pattern still looks great on the ring gear. In fact, you can start to see the "real" wear pattern working the black stuff off the gear faces and it too looks great. The pinion wear marks seem pretty darn close to the beginning of the teeth and end about 1/8 of an inch from the end of the tooth. Engagement point seems a little too low, but the pattern says if anything, I can add a little MORE pinion shim which would engage the pinion even sooner.

the pinion preload was a little tight, so I added .001 shim to the solid spacer. Total pinion preload is still a bit high (per Toyota) at 9 inch pounds. (including seal drag, so I bet it is really only 8. ZUK runs even more than this though, so I think I'm OK there.) Besides, have you seen the size of the V6 pinion bearings? There is slight chatter on the pinion bearings which bothers me some. maybe 1 inch/# difference. And here is why:

There was debris damage on the end of 1 carrier bearing race so I replaced both bearings and races. (they were reused carrier bearings, and I guess I stirred up a little metal in there. This infected the big pinion bearing and put a few dings in the rollers. I left them this way though.

Put it all back together and had a nice dinner with Lin.

Total preload was also a bit high at 20 inch pounds, but I'm not surprised. I went the ZUK route and cranked 100ft/#s of torque on the carrier bearings (while maintaining backlash) I get the best pattern at .006 backlash which is still in spec. (one checking point runs all the way up to .007)
So, The gears are set on the tight side, with the carrier bearing preload cranked up and the pinion pre-load about .001 too tight too.

What did I do to induce the whine? I'm guessing the damage to the pinion bearings? simple harmonic of new, rough gears? cheap gears?

How many of you would go in a third time and replace pinion bearings/races? How many would drive on, just try not to go the annoying 43 MPH and wait to see if they break in OK and hold up on the trail.
I'll try not to smoke this new diff on my 30 mile commute tomorrow. This is the only time I''ve ever WISHED for a traffic jam!
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