Saturday, July 24, 2010

Swing arm suspension

The coil springs of McPherson Struts are always under great compression, even when the unit has been removed from the car. NEVER contemplate stripping the unit unless ALL spring tension can be removed from the top plate by using spring compressors as shown. At least two compressors of the type shown must be used. Alternatively, larger tools which grip two coils in 'C' shaped brackets are available, and arguably safer. It would only take a service centre mechanic a few minutes to strip and rebuild a McPherson strut, so
unless you possess suitable facilities at home, have the job done professionally — it won't cost a lot! (Courtesy Au todata)
Torsion bars with splined ends are attached to spring plates which in turn are connected to the axle hubs. A damper connects an extension of the torsion bar housing and the axle hub. The drive shafts have universal joints (UJs) only at their inboard ends, and their angle in relation to that of the road wheel is thus constant.
To strip the suspension, chock the front wheels, slacken the hub nuts (use a six foot long lever for this) and the rear wheel nuts, raise the rear of the car and support it on axle stands placed under the rear ends of the heater channels (with wood packing). Remove the rear wheels.
Slacken off the brake adjusters and remove the hub nut, then remove the brake drum. If it sticks, try tapping it with a leather-faced mallet to free off the brake shoes. Dismantle the brakes (see appropriate section of this chapter).
Use a sharp chisel to make a mark across the trailing arm and the axle housing flange, so that they can be re­assembled in the same positions. Disconnect the damper lower end, and either swing it out of the way or undo
the top fastening.
The axle tube is secured to the swing plate by three bolts; undo these, and pull the axle tube away from the plate. Remove the torsion bar end cover plate bolts and the cover. Now for the interesting bit. The spring plate is under considerable tension when on its ledge and, when it comes free from the ledge it would fly in a downwards arc with considerably force if you were to choose to remove it by tapping it from behind. Alternatively, you could use a long lever with a cranked end to get the plate off the stop ledge and slowly release the pressure.
When the spring plate is off its ledge note its position carefully, because you'll have to get it back in exactly the same spot if you don't fancy having a lop-sided car! To raise the rear suspension ride height, incidentally, you re-fit the plate one spline further and vice-versa to lower the car. Re-fitting involves using a trolley jack under the plate to 'wind up' the torsion bar until the plate can be slipped onto its ledge. Replace the two large rubber bushes as a matter of course. To remove the torsion bars, remove the rear wings then pull the torsion bars out of their casing, noting their positioning so that they can be replaced accurately. The splines on either end of the torsion bars are of differing size, so that by moving either the inner splines one notch or the spring plate one notch, a wide variety of ride heights can be accommodated for those who like to experiment with that sort of thing.When reassembling, coat the torsion bar rubberbushes with talcum power before re-fitting. Use a trolleyjack to raise the spring plate over its stop ledge, then use long bolts to pull the torsion bar cover plate down and so force the spring plate fully home onto the torsion bar end.

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