Working on a 2008 Chevy Impala Rear Suspension
So you want a diagram. Good. The rear suspension on these things is straightforward enough that you don't need a manual, but it still helps to know what you're looking at before you start wrestling with it. The basic layout is independent double-wishbone in the rear, which is unusual for a full-size sedan in this price range. Most of its competitors ran trailing-arm setups. General Motors went with A-arms front and back on the Impala for the 2006-2013 generation. Here's what you're dealing with when you pop the trunk liner and look down at the rear:
- Lower control arm (A-arm) — cast aluminum, bolted to three chassis points
- Upper control arm — smaller, also aluminum, connects the knuckle to the body
- Strut assembly — MacPherson-style, runs vertically through the lower arm
- Tension rod (track bar) — keeps the axle/hub assembly from shifting laterally
- Coil spring — wraps around the strut, sits on a rubber isolator
- Rear sway bar — 22mm hollow bar, links both sides via small rods
2008 Chevy Impala Rear Suspension Diagram
For an actual image diagram, your best bet is the GM service information system or a site like AutoZone's repair guides. Free ones tend to be low-res and sometimes label parts wrong. The one from GM Techline or even the Haynes manual PDF will show the complete assembly with fastener torques and part numbers. Don't bother with random forum images unless you're just trying to identify a vague shape. I found that the official diagram from Delphi or GM Genuine Parts is worth screenshotting before you start. It shows the bushing orientation on the lower control arm, which matters more than people realize.
The real stuff nobody puts in diagrams
The control arm bushings on these are rubber-and-polyurethane hybrids. They don't fail catastrophically. They degrade slowly over six to eight years, and by the time you notice the symptoms, the car will feel vague in lane changes and the rear tires will wear unevenly on the inside edge. I had a customer bring in a 2008 Impala with 92,000 miles that was chewing through rear tires like they were free. The alignment specs were fine. The bushings were just shot. I replaced the lower control arm assemblies (the bushings come pre-installed on aftermarket units from Moog and Dorman) and the tire wear stopped immediately. You can press in new bushings if you're feeling masochistic, but it takes about forty-five minutes per side with a proper shop press. The pre-assembled control arm swap takes maybe twenty. Another thing: the tension rod bushing. It's small, it's easy to ignore, and it's the #1 cause of vague rear-end feel on these cars. The rod connects the differential housing area to the frame rail. The bushing at the frame end cracks and allows slight lateral movement. When you go over a bump, the rear toe changes by a fraction of a degree. You won't notice it on an alignment rack because they don't load the suspension the way driving does. If your Impala feels like it's floating or wandering at highway speed and the front end checks out fine, look at that tension rod bushing. Costs about eighteen dollars for the bushing alone or sixty for the whole rod assembly.
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Strut and spring replacement
The rear struts are not load-bearing in the traditional sense—the spring carries the weight. But they do control damping and some lateral positioning. Replacing a rear strut is not hard. You need a spring compressor, or better yet, buy a complete strut assembly with the spring already compressed and installed. That saves about thirty minutes and eliminates the one part of this job that can actually hurt you. The lower mounting bolts are 18mm, usually around 74 foot-pounds torque. The upper nuts inside the trunk are 15mm. Penetrating oil helps. These bolts get crusty. I always carry a 15mm socket extender because the trunk access is tighter than it looks. The coil spring isolators—those little rubber cups the spring sits in—are cheap and easily overlooked. If you're putting new springs or struts in, replace them. They cost maybe four dollars a piece and they prevent metal-on-metal noise that sounds like loose change rattling in the trunk over bumps.
Sway bar links
Short, unglamorous, and they fail constantly. The rear sway bar end links on the 2008 Impala are the same design GM used across half their platform vehicles. Ball-joint style with a rubber boot. They develop play from about 70,000 miles onward. The symptom is a clunk when going over single-wheel bumps or turning into a driveway. You can test it by having someone rock the car side to side while you watch the links. If one moves independently of the other, it's done. Replacement is five minutes per side with an 15mm wrench and an 18mm socket. Don't overtighten these. They have a torque spec for a reason—usually around 22 foot-pounds—and crushing the boot while torquing them down just makes them fail faster. The 2008 Impala has adjustable camber at the rear through shim placement on the lower control arm mounting points. Toe is adjustable via the tension rod. Caster is not adjustable. If your lower control arm is bent from an impact, you're going to need a new arm because you can't correct bent aluminum. I've seen people try to hammer them straight. Don't. The geometry won't be right and the structural integrity is compromised. Factory specs for the rear are roughly zero to negative 0.3 degrees camber and zero point five degrees total toe (combined both wheels). If you're doing your own alignment, those numbers are close enough for general driving. If you're tracking the car or pushing it hard on canyon roads, get it done properly. The rear suspension geometry on this car is dialed in decently well from the factory, but it's sensitive to even small deviations.
What the diagram won't tell you
One thing that catches people off guard: the rear brake caliper bracket bolts are notorious for seizing. If you're removing the knuckle for any reason—replacing a bushing, swapping the strut—you'll need to remove the caliper brackets. Those bolts are small, exposed to road heat and brake dust, and they love to break off. I keep a slide hammer puller and a left-hand drill bit set in my kit specifically for this. If a bracket bolt breaks, you can sometimes drill it out with a left-hander while applying breaking torque in the removal direction. Works about half the time. The other half requires a welding extractor or cutting it out with a Dremel. Neither is fun with the suspension partially disassembled. If you need the diagram for reference while you work, print it out and laminate it or put it in a document sleeve. Shop conditions make paper diagrams deteriorate fast. A crumpled, grease-stained printout of a suspension diagram is about as useful as a blank sheet of paper.
