Rear shocks bang?

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Fluery
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Rear shocks bang?

#1 Post by Fluery » Thu May 08, 2014 11:36 am

Hi
Not sure if my rear shocks need replacing of not. Whenever I go over a pothole or over a speed hump the rear end bumps harshly and makes an audible bang. Even cats eyes cause a harsh ride.
Bouncing car up and down doesn't replicate the problem.
Any suggestions?
Thanks

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Alec
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Re: Rear shocks bang?

#2 Post by Alec » Thu May 08, 2014 11:53 am

Hello Fuery,

perhaps the general term of 'shock absorber' is misleading because they don't. They damp the spring's movement. The usual test for the dampers effectiveness is to push on the suspension and the car should return to normal height and stop, if they are ineffective then the car will oscillate up and down for a few cycles. Having said that, if the dampers are getting weak the car may bottom more easily.
Does the car seem low at the back, as the springs may be tired?

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Re: Rear shocks bang?

#3 Post by Mike Stevens » Thu May 08, 2014 11:58 am

The dampers (as Alec correctly called them!) have rubber bushes top and bottom. It is possible that these have perished, thus allowing metal to metal contact.

Relatively easy job to fix - once you've got the bottom damper nuts off! Remember to keep the car's weight on the swing arm though!

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Fluery
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Re: Rear shocks bang?

#4 Post by Fluery » Fri May 09, 2014 10:04 am

Rear end isn't sagging and on bounce test car settles very quickly.
When you say support cars weight on the swings arms, what do you mean?

Appears previous owner had very low air pressure in rear tyres to help absorb bumps.

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CAR
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Re: Rear shocks bang?

#5 Post by CAR » Fri May 09, 2014 10:14 am

If you undo the rear shocks the trailling arms have nothing to stop the springs extending fully and escaping. If you had the rear suspension in front of you it would be easy to see what we mean.
Support the underside of the trailling arms on an already jacked up car with a trolley jack or such like.

I would look at the rates of the rear springs incase they are very heavy duty (does the matter improve with weight in the rear seat and boot?) and also the condition of the spring insulators, originally rubber but very often polyurethane now, to make sure they are still intact at the top and bottom of each coil spring. Also check the rear subframes that they haven't broken at the large rear bush mounting in the rear floorpan, also the floorpan itself.

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Re: Rear shocks bang?

#6 Post by johnconradlee » Fri May 09, 2014 11:13 am

Along with the sub frame mounts I'd also check the diff mounts, the exhaust mounts and anything else at the back of the car that might be loose or broken and produce a bang when you go over a bump. Assuming the rear shocks have been on for a long time I wouldn't even bother wasting WD40 to get the nuts off the bottom, I'd get the nut splitter out as they're easy to get at and 2 plain nuts and 2 half nuts won't break the bank.
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Re: Rear shocks bang?

#7 Post by Richard B » Fri May 09, 2014 3:19 pm

It could be that the bottom stud on the shock absorber has snapped?
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Re: Rear shocks bang?

#8 Post by TRPi » Sat May 10, 2014 11:41 am

Hi

I once had gas shock absorbers (tried a Saab 99 type). Because of very high pressure they gave bad sound whenever there was a bump on the drive path.

JS

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