Trailing Arm Assembly: DIY Replacement Tips

Replacing A Trailing-Arm Assembly

A DIYer shares the ups and downs of the process.

There are several reasons why a motorist might change their front or rear control arms or trailing arms. Worn-out bushings, rust or integrated ball joints are a few. But sometimes, circumstances dictate replacing whole units rather than individual parts.

In a recent situation that required a new trailing arm, I initially had an ABS/traction-control code pop up on my wife’s BMW. She said that the dash looked like a Christmas tree, which is always a bad sign. I test-drove the car and tried to cycle the key a few times to no effect. The issue was going to require further investigation.

A month or so before this, I had replaced the rear brake pads and resurfaced the rotors. When I popped the rear wheel off, I noticed a significant amount of rust around the axle nut that the BMW logo cap usually covers when the wheel is on the vehicle. The axle nut appeared to be flaking off on the sides with rust. At the time, I didn’t think this was a big deal because I didn’t plan to remove the axle. I cleaned it out the best I could and moved on.

But, no good deed goes unpunished. Now the ABS and EPS lights were on. I suspected it was coming from the left rear, but I needed to confirm which wheel was the problem. I borrowed a scanner that could read the ABS wheel-speed sensors as I drove down the road, and sure enough, the left rear sensor was dropping out of range.

At this point, my diagnosis pinpointed the wheel-speed sensor, which was an easy enough replacement. I removed the sensor but suspected that the reluctor ring at the end of the axle encased inside the rear trailing-arm housing might have some rust jacking, causing an erratic reading.

No problem. I decided that the axle was in good shape and would only need a new reluctor ring. With a new ring on order, I went about removing the rear CV axle. I was concerned about the rust on the rear axle nut at this point but had enough heat, hammers and die grinders to remove it. Eventually, I was able to cut it off with a carbide bit. I thought I was home-free.

After removing the bolts on the inner CV joint and making sure there was enough clearance to pull it out, I tried to use a punch and hammer to knock out the axle from the wheel hub. That didn’t work. I went to my local parts store and rented a puller attached to the hub to drive out the axle with a large center bolt. That didn’t work either. I tried several impact guns and breaker bars with heat, and still, nothing.

Last Resort

I was beginning to lose hope. I used an induction heater, thinking that I could get it glowing red hot and break the rust lock. But that wasn’t working either. Every tech finds his or her self in this situation at some point, where everything you’ve tried isn’t making a difference. So I decided to get a new axle with a new reluctor ring and just do my best to hammer out the old one. I couldn’t get it to budge no matter what I tried.

Trailing arm from a salvage yard
I tracked down a trailing-arm assembly from a local salvage yard.

There was a sinking feeling when I realized the only way to remove this thing and fix the problem was to remove the whole trailing-arm assembly. It was my last resort. Fortunately, I was able to locate a salvaged unit from a local salvage yard for $80. It was a massive arm that included the hub and a wheel-speed sensor.

I knew that I had to mark the lower control-arm cam bolt’s locations and do my best to mark the upper mounting bracket as well, so the alignment wouldn’t be too far off. After rolling around on a creeper in my driveway in the middle of winter and fighting through snow, I finally got the new axle and trailing arm installed. The Christmas-tree lights went off, and traction control was back to normal.

It felt like I had finally won the fight. The lesson learned from my perspective is that you don’t want to block your third car in the driveway when you attempt to resuscitate your wife’s car. I had to give up my vehicle for a few weeks while I grappled with what to do and when the weather would cooperate enough to make the repairs. But victory is sweet after you win battles like these.

You May Also Like

Assault on Batteries

Even EV batteries aren’t immune to the effects of extreme winter weather.

EV Batteries

This winter, extreme weather patterns have been disrupting daily routines nationwide. Flooding, snowfall and subzero temperatures all have taken a toll on our roadways and vehicles, leaving many stranded or unable to leave their homes. For those who can make it out to the streets, driving conditions can be hazardous. Having a reliable, fully charged battery is critical during these weather events.

When Springs Break

Unfortunately, the kind of spring break that leaves ‘road earrings’ isn’t a desirable getaway.

Broken Springs
Check the Part: Return Guide for Fluid Reservoirs

Dorman recommends these four steps to determine if it’s a valid warranty claim.

Fluid Reservoir
MAF and MAP Sensors

These small-but-mighty components play an outsized role in keeping fuel-injected engines running smoothly.

MAF and MAP Sensors
Mastering the Multimeter

It’s a tool that will expand your diagnostic ability.

Multimeter

Other Posts

Electronic Parking Brakes

Safety, convenience and holding power – what’s not to love?

Electronic Parking Brake
Navigating the Lubricant Labyrinth

A surge in specialized engine oils has led to some confusion over the correct recommendations for each application.

Motor Oil
Driveshaft Dynamics

Don’t let the terminology trip you up.

Driveshaft
Serpentine Belts Have a Strong Supporting Cast

Tensioners, balancers and pulleys are working behind the scenes to maintain harmony under the hood.

Tensioners and Pulleys