Gears and backlash

JKEmmy

JKEmmy

New member
Hey everyone. So I have a 15 unlimited Sahara. So a Dana 30 up front. I have also regeared to 4.10s. I have never installed a locker so I had a shop install an ARB air locker for me. When I picked up the Jeep I asked what the backlash was and he said he took out the previous gears at .12 so he put it back at .12. Reading around, that sounds a little sloppy. I'm seeing .10 at the most. Not sure if it's different for the ARB or because I'm running 4.10s now. So is this a little loose? Should I adjust? And if I do will this change my gear pattern? Can I get away with just popping open the diff and adjusting those tension rollers on each side? Thanks guys.
 
What the fuck? No. Backlash is supposed to be between .006-.010. That guys sucks. That little bit of change will most likely not change the pattern.

You don’t have tension rollers in there, you have shims. If it’s this bad now I doubt there’s even enough preload on the carrier bearings. If there is, try finding a .005 shim on the drivers side and moving it over to the passenger side of the carrier. Then check the pattern.


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JKEmmy said:
Hey everyone. So I have a 15 unlimited Sahara. So a Dana 30 up front. I have also regeared to 4.10s. I have never installed a locker so I had a shop install an ARB air locker for me. When I picked up the Jeep I asked what the backlash was and he said he took out the previous gears at .12 so he put it back at .12. Reading around, that sounds a little sloppy. I'm seeing .10 at the most. Not sure if it's different for the ARB or because I'm running 4.10s now. So is this a little loose? Should I adjust? And if I do will this change my gear pattern? Can I get away with just popping open the diff and adjusting those tension rollers on each side? Thanks guys.
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Assuming that you wrote the numbers wrong and you’re at .012 inches which is on the high side. If you meant .12mm then you’re a little tight. I believe the range is .006 to .010 inch or .15mm to .25mm. I’m not familiar with any “tension rollers”. Backlash is set with shims to shift the carrier from side to side
 
O crap sorry I missed a 0 it's .012. but that's still a little sloppy I thought. So we have shims for adjustment not rollers ok. So I would have to remove the locker and shim it? Do I need to remove the front drive shaft again as well?
 
In all honesty, you’re probably ok at .012”. The fact that you’re locking a 30 is a bigger concern.
 
That 30 will be fine, I have chromoly shafts and reenforced c gussets .... I also wheel slow.... I don't bounce the Jeep of things, at least try not to ha. I usually don't upgrade either until I break it....... Helped the wallet some.
 
JKEmmy said:
That 30 will be fine, I have chromoly shafts and reenforced c gussets .... I also wheel slow.... I don't bounce the Jeep of things, at least try not to ha. I usually don't upgrade either until I break it....... Helped the wallet some.
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It's your money, but ARB money would have been better spent upgrading to a better axle, IMHO
 
I hear ya. Half the fun is fixing breaking building and learning for me so I guess time will tell. Solid advice for sure thank you. If I had the money I'd put 60s under there. Which I hope to do one-day.
 
A.J. said:
With an air locker they are outside of the bearings not inside. At least they are on the one I just broke.


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Lol, I honestly have never messed with one that had a locker in it. Well, not a selectable locker anyways. We have a JLU scheduled for a re-gear and the customer wants an ARB if the D30. Some people just have their minds made up.


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Ouch lol.... Yeah that's why I wanna make sure this backlash is right! One less thing I gotta work about I hope being in this 30.
 
Awesome thanks guys..... I'll probably leave it. I don't hear any movement or anything. Hopefully it's good so I have time to save up for a new axle haha.
 
0.002" excess backlash on used gears won't hurt a thing in itself. Assuming the ARB was installed with a housing spreader and has correct preload, it'll be fine.

Let's say you install new gears and set the BL at an acceptable 0.010". Within a thousand miles that will open up another 2 thou easily. Bearings wear a llittle, the gears break in a little, etc. That's just part of it. Another reason competent installers will set them up on the very slightly tighter and deeper side. So they are dead nuts in spec once broken in.

The fact he reinstalled to where the BL was before will also make sure the contact pattern remains unchanged. Assuming it was good before, now everything is right back was it was. Changing the pattern on used gears will very likely cause new noise to be generated. Decreasing BL will also tighten up the pattern.
 
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