Know How Notes: What Are Body Mount Bushings?
Most modern cars are built as a single shell, where the body is also the frame. This is called “unibody”. Older vehicles, typically 1996 and older, and almost all years of trucks, are built with separate bodies and a frame chassis. The frame holds the engine, suspension and the supports the body with rubber bushings, anywhere from 6 to 12 separate points. The body mount bushings cushion the ride, but over time they break down.
The factory rubber body mount bushings lead a life of unsung servitude. These bushings ride between the frame and body, cushioning road and engine vibrations from the body. As they wear out, however, the jambs slowly start to lose their alignment, the hood and trunk get harder to open and close, all because the body mount bushings are worn out and one side sits lower than the other, tweaking pretty much everything. Sometimes, the entire car seems to lean to one side. The only solution to worn out body mount bushings is total replacement.
Signs Of Worn-Out Body Mount Bushings
Some signs are obvious, and others are hidden away. Some obvious signs are misaligned doors and fender gaps. If you have to yank on the door to open it or slam it several times to get it to latch, chances are, the bushings are worn out and the body is in a bind. Another easy to spot sign is in the fender and door gaps. When the body sags, these areas move around, so you may have a really big gap at the top of the fender, while the bottom of the fender is really close, even touching, the bottom of the door. If the door catches the fender, you could cause some serious body damage.
The hard to spot symptoms are the ones that cost you the most. The most common is in the front and rear windows. If the body sags enough, the window seals could open up and cause a leak. Over time, the incoming water could rust out the window frame, floor, and the inside structure of the cowl. In the rear of the car, this leads to trunk, rear deck, and quarter panel damage.
Types Of Body Mount Bushings
There are two types of body mount bushings – factory rubber or polyurethane. The nice thing about polyurethane bushings is that they will only need to be replaced once; they won’t wear out like the original rubber bushings. Rubber bushings may be slightly softer, but they also will absolutely wear out again, leaving you in a similar position.
Not all bushing kits are created equal. Some kits come with just the bushings, while other are more complete with washers and the inner sleeves required to locate the bushings together. This varies by make and model as well. After 35-plus years on the road, these metal bushings are going to be in rough shape. The bad thing is that they are often not reproduced, so the originals need to be saved.
Body Mount Bushing Replacement
There are two process used in swapping the bushings. One involves complete removal of the body, such as in full restoration, the other method does not require completely removing the body. Care must be taken, as the body will be separated from the frame in both methods. The second method involves loosening all of the bolts, and lifting the body on one side, replacing those mounts, and then lifting the other side. This process takes patience and careful planning, as the body will be raised about 5 inches above the frame. If the jack were to slip, no more hand. Your local NAPA AutoCare Center would use a lift to safely raise the body.
Installing the bushings takes a few hours to complete. With new bushings installed and torqued down, the car should be driven about 1000 miles and the bushing bolts re-torqued to ensure the bolts are tight after the initial settling.
Check out all the frame & suspensions parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on body mount bushings, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.