Ring gear backlash question

[RWBeringer4x4]

Hey all,

So from what I've read, my differential should have a ring gear backlash between 0.006 and 0.009. I pulled the old oil seal out of my diff, inspected the shims and pinion bearings, then torqued everything down to ~165ft.lbs. via the pinion nut to check preload/backlash.

Of course, I have lost my fish scale, so I haven't checked preload, but it seems "normal," probably something in the low in-lbs range. I'll confirm later. It spins easily, no in/out or side to side play in the pinion.

Then I measured the gear backlash and, over several measurements around the ring gear, was reading between 0.009 and 0.012. In most places I was 0.011. My understanding is that this is too high...

I wasn't having a problem with the diff (it's the front, so rarely ever used) I just figured I'd check it while it was out of the truck. Will the cause major issues if I run it, or am I being overly cautious?

 

[Pin_Head]

The backlash spec is for new gears, so you would expect well used ones to have more backlash. I would run it as long as the pinion preload is fine.

 

[Tools R Us]

Have taken many out that were in that range or looser, but might as well tighten it up while it's out? It an easy adjustment, just move the carrier bearing adjusters to tighten it up, loosen one tighten the other till you see the number that you want. Zuk has some good info, this one likely have what you need? http://www.gearinstalls.com/troy.htm

 

[Tools R Us]

The backlash spec is for new gears, so you would expect well used ones to have more backlash. I would run it as long as the pinion preload is fine.

Agree, but loose is weak and tight is strong. I always bring them back to ~.008" and tighten the carrier bearing preload when they are out.

 

[Pin_Head]

I was thinking that it was still installed in the axle housing. If it is out, then it is easy to adjust and I would set it back in spec. Make sure your carrier preload is in spec too.

 

[RWBeringer4x4]

Of course one of the clamps on my cheap dial indicator stand snapped, so I'll have to figure out how to rig that to check any adjustments.

I thought the ring/pinion backlash was set by the shims in the pinion - those shims only affect preload?

I'll get an official torque spec when I get back.

 

[FJ40Jim]

Pinion depth is set by a shim on the pinion bearing.

Generally, the pinion depth is set first, then the carrier is walked sided to side with the adjusters nuts to get the lash correct.

 

[Pin_Head]

Pinion depth is set with a shim under the inner pinion bearing. Pinion preload is set with shims / preload washer on the outer pinion bearing. Backlash and carrier preload are set using the adjuster nuts on the carrier bearings. See the FSM for further details.

 

[firestopper]

Pinion depth is set by a shim on the pinion bearing.

Generally, the pinion depth is set first, then the carrier is walked sided to side with the adjusters nuts to get the lash correct.

This is exactly what worked for me. It really helps to have a jig for those critical (accurate) measurements.

 

[RWBeringer4x4]

I stand corrected - I'm not in spec for the pinion torque either. So light it doesn't even register on the wrench:

 

[Pin_Head]

Take .001 inch off the pinion preload washer, torque the nut back on and try it again. Repeat until you get the proper preload. You need to remove the seal and outer bearing to get at the preload washer.

 

[RWBeringer4x4]

Well, there's no seal currently in it - that's the right way to do this right? I'm not sure I have anything to accurately remove such a small amount of material evenly...

What is really confusing is that this diff was working fine. Plus, it's the front diff - so it hardly sees any use. The couple times I've had it in 4WD it wasn't whining or sounding problematic. When I had the pinion apart (shims out, etc.) the bearings and races appeared to be in good shape. I'm kind of surprised to find everything out of spec. I'm wondering if I'm doing something wrong here...

The rear differential is still in the truck (although the axles are out). I didn't measure it today (ran out of daylight) but the preload on the rear seemed equally light...

Is it common to have the grind down the preload washer, or is this a "quick fix" to some bigger issue?

Sorry, not a great picture, but the preload washer is the one one to the right of the bearing, correct? The one sitting on top of the bearing is the only shim. If I do have to grind the preload washer - do I grind from the beveled side, or the flat side?

 

[Pin_Head]

The preload washer is the thick one. These came in a set of about 20 in increasing thickness by .001 and you just picked the one you need. I think that they are no longer available. You can thin them pretty quickly using 240 grit silicon carbide paper on a piece of flat glass with kerosene as a cutting fluid. It takes about 50 8 inch long strokes to sand off .001. Use a micrometer often. I don't think it will matter which side you sand. Maybe do both.

You can have 0-3 thin shims, depending on the thickness of the pinion depth shim.

 

[shawnfj40]

You could also just use a crush sleave to replace the shims.

 

[RWBeringer4x4]

My concern here is really one thing:

Is it common for the preload to get this much more loose? Particularly in a differential that probably hasn't seen 20,000mi in its lifetime? This doesn't make sense to me - and before I start removing material from a NLA washer, I really want to make sure I'm not doing something wrong...

 

[FJ40Jim]

Will the cause major issues if I run it, or am I being overly cautious?

Yes, you're worrying about a non-problem.

If the diff has been run it will be looser than new spec. The design is pretty robust. If it is off by plus/minus a couple thou, the unit will still operate fine. It's a Cruiser thing.

 

[Pin_Head]

Sure you can probably run it as is because it was running fine and it is in front. On the other hand, you have it out and apart and you can easily make it right. Your choice.

 

[RWBeringer4x4]

Yes, you're worrying about a non-problem.

If the diff has been run it will be looser than new spec. The design is pretty robust. If it is off by plus/minus a couple thou, the unit will still operate fine. It's a Cruiser thing.

Sure you can probably run it as is because it was running fine and it is in front. On the other hand, you have it out and apart and you can easily make it right. Your choice.

I'm trying to err on the side of "proper" maintenance - I have a tendency to try so hard to get everything into spec that I just break it worse

I'm not so worried about the backlash at this point but the complete lack of preload. I have it torqued to 160ft. lbs. and preload isn't even registering on a torque wrench...it's effectively "0." My question is - how would this happen? In most front diffs - there's no way enough wear and tear would be put on them to spin the shims and file off some material.

I'm beginning to wonder if I don't actually have the nut torqued, or something. My setup is a little "redneck" but the torque wrench did "click" at 160ft.lbs.

I'm thinking of backing everything out and double checking the shim orientation. I thought I put them in the way they came out, but I might be wrong. That, or the PO was in here, in which case it's almost definitely wrong. Is there a good shot somewhere of the shim orientation? The FSM's pictures are not great when it comes to this - the beveled side of the pre-load washer goes down (toward the pinion gear) correct? It essentially rests on the spacer...Then the thin shim(s) stack on top of the pre-load washer. Then the bearing, then the oil slinger, then the flange, followed by the thick pinion nut washer, and the pinion nut.

Obviously the seal goes in too - but clearly not yet!

 

[RWBeringer4x4]

Sunday night bump for more info. Still looking for:

1. A shot or info on "proper" shim oritentation: Which direction the bevel faces, whether the thin shims go over or under the thick shims, etc.
2. Reasons why a probably lightly used diff would be reading zero preload - seems if anything if the bearings spun and I re-torqued to spec I'd have extra preload...

I looked up some of the thick preload shim part numbers from the FSM - looks like they are still available (or at least showing "in stock" in some places). Maybe it's just the kit of 20 that's NLA? Seems like it might make sense to order a few, since if I had to wager a guess, I'd say the rear pinion is going to come up WAY loose on preload as well (feels about the same as the front).

 

[RWBeringer4x4]

Ok guys - still trying to sort out this differential - just ordered whatever smaller pinion spacers I could find, plus a few of the thicker ones, so I could sand them down if need be. I figured I would take you back to square one, how I found everything assembled, when I took it apart. Does all this look correct:

1. Remove Pinion Nut

2. Under the pinion nut was this large washer:

3. Used a puller to remove the flange. Under the flange is the slinger (seal removed previously):

4. Under the slinger is the bearing

5. Directly beneath the bearing is the solitary thin shim