Front End Shimmy After Bearing Install (+ Where Does This Part Go?)
 

Let me start by saying I know I should have figured this out at the time. :doh: The NAPA front bearing assemblies I installed last week came with this part. I couldn't for the life of me see where it should be installed and none of the 4 how-tos I referenced showed anything like it, nor does it appear in the FSM diagram. I assumed it was the seal within the knuckle that is optional to replace, and maybe it installs from behind the knuckle? But none of the how-tos I looked at explained how to actually replace it. So I left this part out. I haven't taken the truck to be aligned yet but I have a significant shimmy that comes and goes at various speeds and I'm wondering whether not installing this is the problem or at least part of it.

https://i.imgur.com/1RgmFj3l.jpg

Thanks for any insight on exactly how this installs and whether it could be an issue to leave it out.

It looks like the outboard shaft seal, which presses into the steering knuckle back-side. The outer CV joint passes through that seal when you slide it into the splined wheel hub.

So here?

https://i.imgur.com/jDqWovCl.jpg

Looks like I wasn’t looking at the correct diagram. I’ll install these and hopefully solve my problem.

https://i.imgur.com/uDChDbAl.jpg

Yup. It's a tight pressed fit, so not likely your factory piece fell out. If the seal is good, no harm done by not replacing it.

I’m not saying whether that is the cause of the front end shimmy but that looks like an essential part of the hub bearing assembly.

I’ve always bought the full assembly from
Marion Bumper2Bumper Automotive for the last 3 bearing assemblies I’ve purchased for two 4runners and 1 Tacoma now I’m about to make a fourth purchase for my 4Runner. Since buying and replacing the full assemblies I haven’t any further issues.

Never have I experienced a front end shimmy before replacing or after replacing the front hub bearing assembly. The indication for my replacement has always been a loud roaring sound which goes away when making sharper turns at normal driving speeds. Resembles the sound of worn mud tires but if you listen closely there is a sound difference. Also the moving of the wheel front to back when lifted off the ground indicates a bad bearing.

Once I knew what I was looking for, the answer came easily. Leaving this thread in hopes it helps the next person.who runs into this.

Thanks. The driver’s side seal was in bad shape so I’ll do that one and go from there.

@Dsr5drvr , I had no shimmy before but wheel movement as you described on both fronts. I got the fully assembled bearing & hub as well. This seal is a separate piece.

BTW, these from NAPA have a lifetime warranty but don’t pay the price shown at the link. It’s crazy but different NAPA stores have different pricing, something I discovered accidentally while calling around trying to find the parts in stock. First place quoted $209.99 but the next, which had them in stock, said $184.99 then gave another 10% military discount for a final price of $166 each.

FWIW, I emailed Marion & nj636. No reply from Marion & I was already done with the job when nj636 wrote back.

Same issue w/ Marion not responding, so I bought mine from Blue Pit before learning that NAPA has these with lifetime warranty. Veteran's discount is a nice thing also.

The seal won't directly cause vibration in the front wheel. Over time it may allow dirt & water into the wheel bearing and cause it to wear prematurely. But yours doesn't sound like it's been together long enough for this to have happened. Replacing the seal is a good move to protect your new bearings, but it won't correct the vibration problem.

Ensure you torque the CV axle nut accurately to avoid damaging the new wheel bearings. I used an Auto Zone loaner and whatever the shop manual says for the torque spec.

Thanks, I did the same (I’ve got OCD about stuff like torque specs.). In fact, I’m heading to Autozone in a bit to reborrow the torque wrench & 35mm socket.

Any chance the seal can be installed without removing the bearing assembly since it goes on the back of the knuckle? Doesn’t seem the axle could “retract” enough that way.

And I’ll keep looking to sort the shimmy. I had the wheels balanced right before the bearing install. I already knew the bearings were a matter of time but they were the ones who showed me how much play there was in the front wheels. Maybe a rebalance now?

NM re: the install question as @theoutbackdream has a terrific write-up.

No problem removing the old seal and installing the new one with the bearing & hub in place that I can imagine.

Driving in the new seal is a challenge. I used the old bearing dust cap (big black steel cover) as it's the right diameter and can be whaled on without damaging the seal.

The NAPA seals were not hard to install. The diameter of the part that fits into the back of the knuckle was spot on. Driver’s side took a couple of hammer taps on the hub dust cover (brilliant idea to use it as the “punch”) and the passenger side slipped right in. And fwiw, the shimmy is gone, I think b/c the driver’s side seal was so deteriorated that it was allowing some play. (Another thread described how a forum member traced an elusive shake to axle play.)

Whatever the reason, it’s solid again.

I doubt very seriously that the shimmy was caused by not installing the new seals, or from one of the old seals being worn, if that is truly the case then I think the new seals will wear out quickly, the seals have no part in aligning or supporting the axle, it's only purpose is too seal so no dirt and for the most part water gets to the bearing.

It's possible that when you took it back apart to install the new seals that it when back together differently/more correctly and stopped the shimmy.

Either way I'm glad you got it all together correctly and all's good now!!

It does seem odd and I don't have the expertise to know one way or the other, I was just going on the fact it was pronounced before the seals went in and gone after. Got it aligned today and the left caster & toe + right toe were all significantly off.

Driving much better but there's still a wuh-wuh-wuh sound that varies with wheel speed and seems to be coming from the right front. It's faint but definitely noticeable. Sure thought that was going to disappear once the new bearings were in. Guess I'll be spending some time going through the front end noise threads. :frusty: