After a particularly nasty freeze-thaw cycle here in Michigan, the roads are destroyed and I need new shocks on the rear of the tow vehicle. Go figure.
I installed a pair of Gabriel Ultra on the rear in March 2016. After almost two years and roughly 34,000 miles they crapped out. I don’t know if the dampening system was shot, but the mounting bushings on both top and bottom were completely torn away.
At the top mount, there’s two rubber bushings that are clamped down either side of the vans mounting bracket. The top bushing on both shocks was completely gone. The shocks were basically just banging around back there. No dampening. Pot holes at highway speeds were treacherous, the back end would hop all over.
2 years/34,000 miles doesn’t seem like much, but whatever. I bought Gabriel’s because I like the name. Besides, they got a lifetime warranty. The only problem was changing them out in 25° weather. But, it’s an easy job.
This time I picked up some washers to fit inside the lower bracket against the rubber bushings. It looked to me like if there was some lateral support it wouldn’t fail so easily.
Why do we need vehicle shock absorbers? From the monroe.com website:
In their simplest form, shock absorbers are hydraulic (oil) pump like devices that help to control the impact and rebound movement of your vehicle’s springs and suspension. Along with smoothening out bumps and vibrations, the key role of the shock absorber is to ensure that the vehicle’s tyres remain in contact with the road surface at all times, which ensures the safest control and braking response from your car.
What do shock absorbers do?
Essentially, shock absorbers do two things. Apart from controlling the movement of springs and suspension, shock absorbers also keep your tyres in contact with the ground at all times. At rest or in motion, the bottom surface of your tyres is the only part of your vehicle in contact with the road. Any time that a tyre’s contact with the ground is broken or reduced, your ability to drive, steer and brake is severely compromised.
Since I’m talking about travel trailers/fifth wheels, the only action that applies would be keeping the tires on the road while underway, with an emphasis during braking. It’s interesting to note not all trailers have shock-absorbers. I can’t ever recall seeing a leaf spring configuration with shocks. However, all of the Airstream trailers come factory equipped with shock-absorbers on their Dexter Torflex axles. Incidentally, there is no requirement for shocks mentioned in the Dexter Axle “Applications Manual”.
Here’s my experience. It’s a little bit involved, so bear with me.
Our 2008 30′ Slide-out Classic Limited came equipped with GoodYear Marathon ST tires on 15″ aluminum rims. After dealing with multiple tread separation failures (two of them catastrophic; you can read about all that here), I swapped them out in April 2012 for Michelin LTX tires, on 16″ aluminum rims (there were no tires on 15″ rims that meet load requirements- I find it interesting that 15″ ST tires somehow do meet load rating… hmm). Note, I never experienced any strange wear or ‘notching’ on the ST tires; but then, each ST tire never lasted more than 5-6,000 miles, so there was hardly any wear on them, at all. Also something else to note, I never rotate trailer tires. There’s no reason for it with a properly balanced rig, and additionally it would only mask potential running gear or loading problems.
After about two years and roughly 16,000 miles on the larger LTX tires, I started to notice very distinctive ‘feathering’ on the tread. It resembled the type of wear when a vehicle has bad alignment. Fast forward about 10,000 miles, and the treads were not just heavily feathered but had chunks out of them, or what I call ‘notching’.
The Michelin LTX’s had almost 30,000 miles and 63 months when the curbside front tire blew out on a Tennessee freeway. It wasn’t a ‘tread separation’ like the ST tires- that is, it wasn’t a strip of tread coming off the tire, but more like a ‘blow-out’ at a specific point.
Getting it replaced, I had two tire guys from different shops, tell me it looked exactly like what bad shocks will do to a tire at highway speed. Apparently, bad shocks will allow the tire to ‘bounce’ along causing ‘chunks’ to be torn off on the roadway, especially under braking.
I suppose the first thing I should do is check the axle alignment. That might explain the strange wear, but not the ‘chunking’. Or maybe I should just replace the other three and watch what they do. Five years is pushing RV tire service life anyhow.
All the telltale signs for bad shocks were there. Excessive bounce, shimmy at highway speed, and of course, fluid leak stain on the housing.
Michigan vehicle. Twelve years old. Factory original shocks.
Means, we’re going to have a heck-of-a-time getting those jonnies off. The bottom mounts are connected to the radius arm on a welded stud mount. The nut was rusted solid. I thought torching the nut with repeated cherry-red hot and cool cycles would break the rust weld. I was wrong. I sheared those bolts off with only a 3/8″ drive ratchet. In hindsight, I should have given it some PB-Blaster, and let it sit for a few hours.
As it was, I was looking at a busted lower shock mount, and having to replace the entire radius arm just for a new stud. Not good. More money. Lots more time– until I discovered the Dorman Engineering replacement shock mount, model 31001. Has good reviews on the various forums I searched. Looks good to me. We’ll see how it works out.
Here’s the process… since this was my first time changing out shocks, it only took about three hours a side. With this handy-dandy step-by-step, I imagine you could do it in 2 hours total.
1. Loosen the lug nuts.
2. Jack the front end. Support the frame on jack stands, remove the wheels.
3. Cut the lower mount stud off using a recirculating saw and metal cutting blade. Getting the upper nut off is trickier. The shock itself is hardened steel, and cutting through it in such close quarters takes a steady hand (you can get about half-way thru, then work the whole shock back and forth… should snick off)
4. Have a new 1/2″ metal cutting drill bit and a HD drill to port a new mounting hole in the dead center of the existing stud mount location. Once you’ve got the hole drilled, you might need to grind down the thickened stud mount in the radius arm, in order to give the Dorman bolt enough purchase thru the arm.
5. Jack the radius arm up so you don’t have to try and elongate the shock. Fit the upper washer and bushing on the shock, and slip it through the upper mounting bracket. Slip the bushing, washer and nut over the upper shock bolt. This sounds easy, but getting at the upper shock bolt on the driver side is extremely tight. There’s no room to work. My 6 year old would have had no problem getting her little hands in there, but I didn’t want her getting grease under her nails (plus, it was 5:00am on Sunday when I was trying to make this repair… in order to salvage a much anticipated vacation). So, I used my ratcheting wrench and taped the nut into it, then maneuvered it into position over the shock bolt. While holding the wrench, my son then spun the shock itself to tightened it down till the bushings were compressed.
6. Install the Dorman kit on the lower shock hole, then move it into position and slip the bolt thru your freshly drilled hole in the radius arm. Put some blue lok-tite on the bolt, fit the washer, and tighten down the nut to just-shy-of-an-aneurism lb-ft’s.
Voila! You’re done. Or in my case, you’re ready to change out of your rain soaked, greasy Carhartt’s, take a shower, hop in the driver seat and drive the family 500 miles up north. Did I mention it was a torrential rain-storm while we were working?