Loud rear suspension bang when wheel drops
 

Every time the car "takes off" i.e. the weight comes off the rear axle e.g. an inclining undulation or ramp ends and the rear wheels drop suddenly, there's a long bang from the rear passenger-side corner. I've rebuilt the front suspension on two 75s but part from changing a pair of rear springs, have little experience of the rear end.

There's no indication of play in any direction with the wheel jacked up but then it's fully unweighted so that I can't emulate the movement. Any thoughts?

Dougie.

is this the zt you are working on ? i had this exact problem with my 75. in my case i had been supplied with the wrong length shock absorbers, i bought online . they were advertised as r75 rears. indeed they were ,but the seller had not realised that the shocks were for the very last model 75"s ( contempory) . these had the mgzt suspension set up. when i removed mine again and compared the new against the old ones, the new ones were shorter. i wondered why i had to jack up the rear arms so high to fit them. so i would suggest that you check that you have the correct length springs and damper combination if this is in fact your problem. what you could be experiencing is the shocks bottoming out whilst going over road humps , before you have" landed" so to speak. ..... and whilst you dont need much speed for this to occur , it certainly makes quite a thud.

Thanks. I don’t have a ZT any more (see sig). The springs and dampers are original on the rear.

Dougie.

Is the bump stop still in place? If they are the original shocks, it may be that the bump stop has disintegrated?

Item 6 from Rimmer Bros.

https://rimmerbros.com/Item--i-GRID001548

Wouldn’t that cause the issue in the opposite direction I.e. when the damper is compressed?

Sorry, quite right. :o

So when the weight is taken off the wheel, the spring will extend and take up the play from the failed component I guess. This could point towards the top mount, item 4 perhaps?

I saw this on the front of a little fiesta. When the car was on the deck the suspension felt 'loose', but when jacked up the play disappeared when checking by hand. The front top mount had failed.

That's an intelligent suggestion, thanks. I'll look at it when the storm abates!

Dougie.

Just trawling through my old threads this afternoon. I never did anything about this one as I ended up suspecting that the rear springs are too long given the car sits noticeably high at the rear, thus stretching the damper.

The bang hasn't changed in any way either circumstantially or in volume, and I've automatically adjusted my driving to deal with the odd speed hump/kerb/other thing which causes the rear left wheel to drop suddenly. Never been an MoT issue either, twice.

:shrug:

Dougie.

Just asking......
Is it a tourer
& does it have the self-adjusting shock absorbers.?

I have one with them
& whenever the car feels so disposed
it clunks when going over a hump or a kerb
but
I've had no issues with this at MOT time.....
It just does it whenever it feels like it......??? :shrug:

whilst your under there, might be worth checking your subframe bolts failsafe washers are tight and any other arm bolts to the upper and lower ones. you wont be able to get a spanner on the upper arm bolts but may see some play up and down on the subframe once the weight is off the roadwheels. top mounts shocker bolts also need checking , but i still think its a length combination between the shocks and spring. happy hunting !! ;)