Backlash

[PaulS]

As you can tell by my posts, I'm moving forward (albeit slowly).  Forward is good...

Anyway, I got the carrier reinstalled.  I had to reduce the shim stacks from the original to get it in with the new bearings.  (The book says I shouldn't have to pound to get the carrier in.)

But this thing is anything but smooth.  It is feeling really rough.  I think a good chunk of that is backlash--I measured 0.013", which is clearly too much.  When I held onto the ring gear to stabilize it, things were much smoother.

I measured torque to turn.  It was at 10 in-lb without the carrier in place.  With the carrier/ring gear, it is jumping back and forth between 20 and 50 in-lb.  Like I said, I think most of that jumping is from the backlash.  (I didn't measure torque while holding the ring gear, but I don't think it would be valid anyway.)

Will getting the backlash below 0.010" (and preferably down to 0.007") make things smoother?  I'm thinking I'll need to add shims behind the inner bearing (the larger pinion shims) to move the pinion inward, correct?  How much should I add to reduce backlash by 0.003-0.006"?

But since I have the same pinion bearings, same gears, and I never even pulled the inner bearing, so the shims there are untouched, why do I need to do this at all?  I can't see how new carrier bearings would have done this...

Anyway, I'm glad I didn't put the oil seal in yet!  That thing will be the very last thing put onto the axle housing!  I won't be surprised if I'm pulling that pinion shaft another two or three times before I'm done.

-Paul

[bretto]

To change the backlash, you shim the carrier side to side, moving it closer or away from the pinion.  All the while keeping the same preload on the carrier bearings.
Setting gears can be tricky balance juggle.  Even more so with a used set because they are already broken in or set.  You generally should concentrate on getting a good pattern and try to balance the specs in with that.  I think I remember being told once on a used set you concentrate more on the coast side pattern.
I'm sure you have seen a many website about setting gears, but here is a good one.
http://www.pirate4x4.com/articles/tech/billavista/Gear_Setup

[Carls_jeep]

If you change the location of wear on the ring gear/pinion gear you may end up with a loud rear end. Try to put the wear pattern back in the same location as it was.

[PaulS]

That's an awesome article Bretto!  Thanks for the link.

I've got the backlash at 0.006" now, and it's a lot smoother.  (Not perfectly smooth, though.)  Turning torque jumps around 20-30 in-lb, which I think is pretty good.  (Pinion alone was a smooth 10 in-lb--at the low end of the range in my service manual, but still in spec.)

I'm going to do a contact pattern test before anything else, though.  (I'm presuming I can pick up gear marking compound somewhere like NAPA.)

But man, I wish I had a spreader.  I really don't like banging on the bearings with the dead blow to try to get the carrier into the case.  How can I be sure I haven't damaged them?

-Paul

[bretto]

I just used oil paint from the craft store thinned with a little gear oil to mark the teeth.  I have a better time seeing the pattern with Prussian Blue paint over a yellow color.