4WD Truck Pulls Left Then Right Then Left Then Right

The Problem

Every once in a while, my truck would pull left then right, then left, then right, and eventually settle down and not do it again for weeks. It started out as a very faint pull to one side, then the other. I thought something was wrong with the power steering gear box. Then I noticed it would sometimes start doing this after going around a corner. This week, I almost hit a curb going around a corner because the steering didn't return to center like it normally did. I had to force the steering wheel back to center.

Here's a video of the truck pulling left then right.  I was doing my best to keep it in a straight line, but it looked like I was weaving a little:

https://www.youtube.com/watch?v=SIU7SdVY1O4

Diagnosis

So I took a look under the truck. I found nothing wrong with any of the steering linkages. I had my son turn the wheel left and right as I watched the steering linkages move. Still nothing wrong. Well, my axle dust shields were shot, but that wasn't causing the problem.

I then jacked up the front axle so the front tires were both off the ground. I turned the manual hub lock on the passenger front wheel and found that the front right wheel would turn just fine as long as the steering was pointed straight. But when I turned the wheel either right or left, the wheel would jam. This was because two of the four joints on the U-joint were binding up.

Why the U-Joint Causes the Problem

This truck is a 2008 Ford F-250 with a solid front axle with U-joints at the wheels. When it's not in four wheel drive, the hubs are unlocked and the front axle doesn't rotate, so the U-joints stay in the same position and don't rotate when the truck is rolling.

When the wheels steer left or right, you can have only two of the U-joint bearings pivot with the steering while the other two don't turn. The axle may stay in the same position while driving as long as it's not in 4WD.

The problem shows up when the axle rotates a quarter turn and the seized U-joint bearings are now in the vertical instead of horizontal position. This makes steering more difficult and causes it to pull to one side or the other. Then when the axle rotates another quarter turn, the problem magically goes away and doesn't show up again for a while.

It's My Fault

I've had this truck for a year and a half and hadn't greased the U-joints in the front axle . . . ever. So I cleaned off the grease fittings and pumped some grease in the U-joints.

For a test drive, I kept the front right hub locked manually, but the switch on the dash was not engaged in four wheel drive. As I pulled out of the driveway, the steering wheel would pull as the wheel rotated. Then it stopped pulling as the grease worked its way into the U-joints.

This wasn't a Ford problem. It was because of bad ownership. The truck wasn't properly maintained and the U-joints lost their lubrication. This steering problem can occur on any similarly configured 4WD pickup with U-joints on the front axle, be it Ford, Dodge, Chevrolet, or other.

What's That Scraping Noise?

After replacing the shocks, I heard a new scraping noise while driving. I'll show you the picture in a minute. 

Since replacing the shocks is pretty easy, it wasn't a blog-worthy project, so I didn't take any pictures. One thing I found wrong was that the front shock top mounts were loose. Maybe that contributed to the shake. I also have a wheel that needs to be balanced, but the new shocks make it ride better.

After installing the shocks, I drove to the corner gas station to fuel up. I was headed to a family get-together about 45 minutes away. After pulling out of the gas station, I rolled down the windows and heard a scraping sound. It wasn't loud, but that noise wasn't there before I changed the shocks. I figured I had better take a look under there and see if I can see what it was. 

I actually debated whether or not I should stop and check, or just keep going. It's a good thing I stopped. 

So I was using a wrench to hold another wrench from getting jammed in the spring while I loosened the rusted bolts on the top of the shocks. It kept dropping, so I'd grab another wrench on the ground and use it. I must have missed the fact that that wrench didn't hit the ground. I also don't have a dedicated place for that wrench since it's not in a set. So that's why I missed it when I put the tools away. 

It's kind of like life. You can see if you can fix those small annoyances, or you can ignore them and risk them turning into much bigger problems. 

Floppy Subaru Visor Failure Analysis

This visor from this 2008 Impreza wouldn't stay up. So after getting a new one, I decided to take it apart to see what failed.

The mounting end can just be pulled out.

After cutting the vinyl cover open, I pried apart the clip.

To separate the two halves, I pried around the edges.

There it is. The plastic surrounding the metal rod had broken. The black metal part that's in the visor below is springy. It squeezes the rod. It keeps tension on the rod to keep it in place. I had to pull the broken parts out before I could get the two halves to separate without breaking it.

Here's the inside of one half.

And here's the inside of the other half.