Advice for DIY Front Wheel Bearing Replacement

Just spent Memorial Day 2023 replacing a front wheel bearing on a 2007 Prius. I have these observations to share with you:

1. Time to Failure. I've experienced about a dozen front bearing failures on qty=5 Gen 2 Priuses in my family over 16 years, so this was not my first rodeo. All of the previous failed bearings were replaced by Indiana shops.

When you first hear the buzzing sound from a failing front bearing you have from 300 miles to ~5k miles before you're walking. This particular bearing was at 5k miles from inception of the buzzing noise and still had some time left. However, the bearing failure during Christmas 2022 mid-Missouri on I-70 went from silence to loud grinding in 300 miles. By loud I mean that even my oblivious wife noticed the noise without prompting.

The odometer readings for Gen 2 bearing failures is from 100k to 200k miles, mostly on the lower end of that range.

BTW, the notion that play or rock in the front wheel accompanies (and confirms) early bearing failure is not correct or at least is unwise and unsafe advice. If you have allowed a front bearing failure to proceed to the point of wheel rocking you've let it go too long. Even when the mid-Missouri bearing was loudly grinding, there was no wheel rock when the car was lifted.

2. Preload the Knuckle with New Parts Before You Start. I pre-purchased used on EBay the aluminum part that holds the bearing assembly. This part is variously called the knuckle or the bearing carrier. To save time I preloaded the knuckle with these items, also purchased from EBay:

a. A Timken bearing assembly, or at least Timken was etched into it
b. A dust shield (stamped sheet metal part)
c. A lower ball joint

The second-hand EBay knuckle came without its bad bearing but the bearing seat was caked with aluminum oxide and salt. I went through a half dozen Dremel sanding drums trying to grind open the seat that accepts the bearing assembly.

3. Loosen Axle Nut Before You Lift the Car. Loosen the axle nut before you lift the car off the floor. The factory original nut is a weird 30mm 12 point device that cannot be removed with a six point 30mm socket. When you buy a 12 point socket (Menard's in the Midwest) get a deep one. Shallow sockets won't work.

4. Remove the Knuckle with the Ball Joint Attached. I could not get the castle nut off the lower ball joint while the ball joint was still attached to the knuckle, and this is one reason I pre-purchased a new ball joint. Better to attempt separation of the ball joint later on the bench when you have time and the job is finished.

5. Consider Pre-purchasing Bearing Retaining Bolts. New bearing assemblies don't come with the qty=4 bolts that secure the bearing to the knuckle. Retrieving these bolts when the knuckle is on the car is difficult. Frankly, retrieving the bolts on your garage bench isn't easy because they are torqued tightly. Hope you have a big a-- bench vise to hold the knuckle while you torque them off.

6. Wheel Speed Sensor Dust Cup. This stamped metal cup keeps water out of the bearing and provides some shielding to the sensor that detects wheel speed. It goes on after the qty=4 bolts securing the bearing to the knuckle are installed and tightened. The dust cup blocks access to the qty=4 bolt heads.

7. Engineering Interns Should be Barred from Practice. The idiot kids that designed the knuckle (probably in the employ of a Toyota supplier) should've had their engineering degrees rescinded. Their major error was ignoring salt-driven corrosion that eventually welds the steel bearing assembly to the aluminum knuckle. You could not arc weld a bearing any tighter to the knuckle than corrosion accomplishes in 100k miles in the Midwest.

Second error was not providing outward projections in the knuckle's profile to assist the poor guy that forces the bearing out of the knuckle with a hydraulic press. The knuckle's design assures that the dust shield gets mangled in the process of removing the bearing assembly.

Third error was not providing a window in the spindle so that someone can force the bearing out of the knuckle by driving qty=4 bolts into the bearing's bores backwards. Rotating the dust shield by 5 degrees will block the holes in the knuckle to make this possible.

Thanks for listening. I'm done.

Jim Olson
Indianapolis, IN US

 

This is all hypothetical about what a revised knuckle design might include, but removing the 4 bolts that secure the bearing assembly to the knuckle would allow the dust shield to spin 5 degrees.

When the dust shield spins 5 degrees it covers the 4 clearance holes in the knuckle. If there were some way to drive the bolts backwards in the threaded bores of the bearing assembly, they would push the bearing assembly out of the knuckle.

I have no idea if this could be accomplished on the vehicle but it could if the knuckle was off-vehicle and the spindle gets equipped with an access window for the 3/8" socket that drives the bolts backwards.

The access window in the spindle could be tiny if the bolts have a female Torx depression in them.