No life (a.k.a. DattoMaster)  
Joined:
2008/10/10 22:02
From Melbourne Australia (and likely under the car)
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the pinion nut is 87-123 ft lbs
don't go for 'either' end of that torque - what you have to achieve is the right pinion preload - which - since it's a crush tube, not a solid spacer, means you start with 87, put a spring guage/length of wire on the diff flange through a bolt hole, and check its resistance to turning. With a new seal in there, it has to be around 6-8 lbs inch (measure the distance from the centre of the pinion to the centre of those holes on the yoke/flange and do the math to get what 'weight' on the spring scale = 6-8 inch lbs. If it happens to be 1 inch, then it's 6-8lbs. IF you happen to have a small/fine tolerance torque wrench, you could adapt it to the socket that goes on the pinion nut, and check the drag/torque, then tighten a bit more, recheck etc. If you have to go beyond 123 ft lbs to get the right drag/preload then do it. With a touch too much preload, they'll last practically forever, but with too little, the extreme forces acting on them will allow the pinion bearing to get an extremely small angularity (almost inperceptible) which then focuses the load on a tiny section of the roller (wheras tight spreads it along the entire length of the rollers).
If you decided to machine up some solid spacers to replace the crush tube, then you play with them till the preload is right, and in that case, I'd be looking at 120ft lbs of torque
If for some reason you weren't running a new crush tube, just changing the seal, you'd have to mark the nut/pinion stud before removal, replace seal then apply a reasonable amt of loctite (not litres, but a nice smear) then re-tighten to that marking. It'll feel a lot less tighter than the above torque figures. Test the drag/preload - it'll probably need to be nipped up a little past there. I wouldn't even try it without loctite (262 most likely would be what I'd use - which is about the strongest, and shouldn't be troubled by the temperature range it'll see)
The manual doesn't specifically list backlash or carrier bearing preload (at least that I can find) - so best I can do is suggest a ballpark based on other similar sized diffs, and experience in general. For carrier preload I'd look at 3thou or a touch more. It's practically impossible to actually get this 'too tight' - you won't break the housing or anything like that, but what I'm saying is that the forces we could put in place to jam it in tight, that's _peanuts_ compared to the side thrust/load under acceleration, as the pinion literally tries to push the crownwheel sideways as they both spin around. NO comparison. You'd likely be wanting around 5-8thou preload on used bearings (and about 10 thou on brand new bearings). that'd actually be hard to achieve without a spreader. Obviously measurements have to be taken precisely, and you need at least one extra shim to measure to find what the clearance actually is, then calculate what size shim is needed to get to the right preload.
On backlash, well I don't know specifics of this diff, but since they are typically measured on the crownwheel teeth, or outer edge, I can translate the specs for a larger diff into degrees (rather than thousandths of an inch of movement on the dial indicator) then re-calculate for a smaller diameter crownwheel.
Anyhoo - that'd be somewhere around 5-8 thou crownwheel backlash for a 165 and 6-9 for a h190
As far as the meshing pattern goes - I can provide pics if anyone needs them - it's much the same for any diff. Opinions vary, but I'd personally be inclined to go for a better contact/mesh pattern even if it put it 1thou outside the backlash max spec. If it results in a very poor mesh pattern to get near the right backlash, there's no way around it, you'd have to remove the rear pinion bearing and swap _that_ shim to alter the pinion depth, and start again with backlash etc
Posted on: 2009/4/16 12:52
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Transfer
