Unit bearing replacement with 16 inch big brake kit

Brian.souhan · Jun 11, 2022

Hi all, don’t believe all parts of this have been discussed, but redirect if I missed something in my search.

Took jeep in for alignment with Firestone and they suggested new unit bearings…which is very early. Took it home, raised it and tested, and a lot of play in the drivers side but none in the passenger side. Given that I’m replacing one, should I just do both sides? While way early (three years), I’m not terribly surprised given my big tires and the fact that the roads around here have manholes that are between 2-3 inches below the actual road, and generally are hit on drivers side more…also I’m an idiot and continue to test for death wobble by sometimes purposely hitting them…and just now have started to see it…so I caused my own issue.

Second question, I have a narrow one car garage, and have managed to do axle swaps and lots of other things, but don’t have much in terms of big tools. Any suggestions on easiest way to grind down the new unit bearings with just a 4 in angle grinder…or should I just eat the extra $100 and buy them pre-machined. That is what I did initially, but I see some people saying it only takes about 10-15 minutes. Will it be that easy with just an angle grinder…does it have to be perfect circular? Just trying to plan this out.

Final question…I see the super 16in doesn’t require the grinding…how much swapping is needed to move to that kit…not likely worth it, but I like to explore all possibilities and I’ve had my jeep for 21 years and will have it forever, so long term investment is good.

Thanks! And again apologize if all of these have been answered.

Claybirdd · Jun 11, 2022

Do it yourself with the grinder. Not that much material has to be removed and will only take 10-15 minutes like you said. That's what I did. It does help to have a vice to hold the unit bearing but not required. I'm sure you can figure out a work around. Save that 100.00 for gas money.

I would just go ahead and do both.

Brian.souhan · Jun 11, 2022

Yeah, need the gas money!

Brian.souhan · Jun 11, 2022

Claybirdd said:
Do it yourself with the grinder. Not that much material has to be removed and will only take 10-15 minutes like you said. That's what I did. It does help to have a vice to hold the unit bearing but not required. I'm sure you can figure out a work around. Save that 100.00 for gas money.

I would just go ahead and do both.

Did you install and then grind off, or grind off before installing…can’t recall where but thought I saw someone ground while installed and just spun it around … or, I can just put in front low, put in gear and let it spin while I grind… good idea or bad idea???

Claybirdd · Jun 11, 2022

I used a vice and ground before installing. Your idea should work fine though.

mrblaine · Jun 11, 2022

Brian.souhan said:
Hi all, don’t believe all parts of this have been discussed, but redirect if I missed something in my search.

Took jeep in for alignment with Firestone and they suggested new unit bearings…which is very early. Took it home, raised it and tested, and a lot of play in the drivers side but none in the passenger side. Given that I’m replacing one, should I just do both sides? While way early (three years), I’m not terribly surprised given my big tires and the fact that the roads around here have manholes that are between 2-3 inches below the actual road, and generally are hit on drivers side more…also I’m an idiot and continue to test for death wobble by sometimes purposely hitting them…and just now have started to see it…so I caused my own issue.

Second question, I have a narrow one car garage, and have managed to do axle swaps and lots of other things, but don’t have much in terms of big tools. Any suggestions on easiest way to grind down the new unit bearings with just a 4 in angle grinder…or should I just eat the extra $100 and buy them pre-machined. That is what I did initially, but I see some people saying it only takes about 10-15 minutes. Will it be that easy with just an angle grinder…does it have to be perfect circular? Just trying to plan this out.

Final question…I see the super 16in doesn’t require the grinding…how much swapping is needed to move to that kit…not likely worth it, but I like to explore all possibilities and I’ve had my jeep for 21 years and will have it forever, so long term investment is good.

Thanks! And again apologize if all of these have been answered.

Do not buy our unit bearings. You can do that yourself in a few minutes with a grinder and a flap disc. It isn't critical, it just has to be smaller than the rotor hat ID by some amount and have a chamfer around the outer edge that does not hit the corner on the inside of the rotor hat that would cause the rotor to wobble.

I would check to see if a stock shaft installed in the unit bearing tightens it back up. If so, then it is very possible that your aftermarket shafts bottomed out on the splines and cause premature failure of the unit bearing. Ignore that if you are running stock shafts.

We pay the same or higher for unit bearings as you do. Then we pay to run them up to the machine shop, pay to get them machined, pay to get them back, and the pay for the shelf space they occupy with a small mark-up so I don't quit doing it. That is a whole lot of extra money for something you can do yourself in a few minutes. Besides, if you buy a pair, that is just that much faster I have to go get another batch done and I really don't like doing them.

mrblaine · Jun 11, 2022

Brian.souhan said:
Did you install and then grind off, or grind off before installing…can’t recall where but thought I saw someone ground while installed and just spun it around … or, I can just put in front low, put in gear and let it spin while I grind… good idea or bad idea???

I install, grind a section, turn it by hand, grind another section, and keep doing that all the way around until the chamfer at the edge is gone. Then I do a rounding grind in the direction of the flange to even out the flat spots I made grinding across the flange. Then I put the chamfer back.

Brian.souhan · Jun 11, 2022

mrblaine said:
Do not buy our unit bearings. You can do that yourself in a few minutes with a grinder and a flap disc. It isn't critical, it just has to be smaller than the rotor hat ID by some amount and have a chamfer around the outer edge that does not hit the corner on the inside of the rotor hat that would cause the rotor to wobble.

I would check to see if a stock shaft installed in the unit bearing tightens it back up. If so, then it is very possible that your aftermarket shafts bottomed out on the splines and cause premature failure of the unit bearing. Ignore that if you are running stock shafts.

We pay the same or higher for unit bearings as you do. Then we pay to run them up to the machine shop, pay to get them machined, pay to get them back, and the pay for the shelf space they occupy with a small mark-up so I don't quit doing it. That is a whole lot of extra money for something you can do yourself in a few minutes. Besides, if you buy a pair, that is just that much faster I have to go get another batch done and I really don't like doing them.

I do have aftermarket shafts so will check that. Had other issues with ten factory shafts, one pair was too long, one pair was wrong spline count, so sadly would not be shocked, but hope that isn’t the issue as ten factory wasn’t very helpful with my previous issues…fortunately was able to back to Amazon, but now outside of that time frame.

Thanks for the direction, I think this should be very doable!

Brian.souhan · Jun 12, 2022

So I ordered the regular bearings, but then after consideration ordered the pre-machined ones as well…I do not doubt my ability given the help received here, but I recall that I live in a townhouse complex and currently rent, and I think I’m not supposed to ‘work’ on my vehicle even in the garage. I’m sure this is pretty standard language, and work is vague, but 15 minutes of loud grinding added to what I already plan might be a bit much. One particular neighbor never has said it bothers him what I have done, but he always comments when I do something…I ask if it bothers him and he says no, but think best to keep it as minimal as possible. I am very gracious that Blaine offers them pre-machined, and given the work I don’t think it is expensive at all (although I’d still rather save the money!).

Brian.souhan · Jun 16, 2022

So I’ve removed the unit bearings and taken a look and compared aftermarket and stock shaft, and the ten factory ones actually have a slightly longer splines, so I don’t think it’s that (actually didnt look at outer hub splines, but checking photo they look ok). Anything else that might cause it…I really can’t explain just how bad the manhole covers are here and it hits hard… it still seems pretty early to go, but only about a 30 minute swap. Any other ideas what might cause premature failure on one side?

As for grinding, having a set of unit bearings on hand, I can actually see how little grinding is needed…but still not sure wise in my place. Could probably even do with a dremel…but would take time!

mrblaine · Jun 16, 2022

Brian.souhan said:
So I’ve removed the unit bearings and taken a look and compared aftermarket and stock shaft, and the ten factory ones actually have a slightly longer splines, so I don’t think it’s that (actually didnt look at outer hub splines, but checking photo they look ok). Anything else that might cause it…I really can’t explain just how bad the manhole covers are here and it hits hard… it still seems pretty early to go, but only about a 30 minute swap. Any other ideas what might cause premature failure on one side?

As for grinding, having a set of unit bearings on hand, I can actually see how little grinding is needed…but still not sure wise in my place. Could probably even do with a dremel…but would take time!

View attachment 337558

You have to put the stock stub in the "bad" unit bearing to see if it tightens it back up to know if the splines are an issue.

Brian.souhan · Jun 16, 2022

mrblaine said:
You have to put the stock stub in the "bad" unit bearing to see if it tightens it back up to know if the splines are an issue.

Ok, will try that…thought if just compared spline lengths and the depth was same or longer it wouldn’t be the issue.

If the splines are the issue, is there a way to fix?

Brian.souhan · Jun 16, 2022

Brian.souhan said:
Ok, will try that…thought if just compared spline lengths and the depth was same or longer it wouldn’t be the issue.

If the splines are the issue, is there a way to fix?

Put together with stock shaft, can’t see or feel any difference…

mrblaine · Jun 16, 2022

Brian.souhan said:
Put together with stock shaft, can’t see or feel any difference…

Is there play in the unit bearing with the other shaft installed?

Brian.souhan · Jun 16, 2022

mrblaine said:
Is there play in the unit bearing with the other shaft installed?

Yes

mrblaine · Jun 16, 2022

Brian.souhan said:
Yes

And that play does not change when you install and torque the stock stub shaft, right?

Brian.souhan · Jun 16, 2022

mrblaine said:
And that play does not change when you install and torque the stock stub shaft, right?

Don’t really have a measurement tool for that, but feel I can’t detect a difference.

mrblaine · Jun 16, 2022

Brian.souhan said:
Don’t really have a measurement tool for that, but feel I can’t detect a difference.

If it isn't obvious then that most likely wasn't the issue.

Brian.souhan · Jun 16, 2022

mrblaine said:
Is there play in the unit bearing with the other shaft installed?

Yes, with both shafts installed there is play limited to the unit bearing…everything else seems solid.

mrblaine said:
If it isn't obvious then that most likely wasn't the issue.

hoping just the nearing it took…I was purposely hitting a lot of potholes to verify I’d don’t have DW…then slowly it started to appear, but jumped to new level after Firestone alignment. Too easy to fix….-anyone wanting some good 37?

Unit bearing replacement with 16 inch big brake kit

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