Rear Knocking..

[Aceman]

Ok, so the Datsun is now on the road again (well, once the number plates turn up!).

Going for a drive around the yard, it's been picked up it has a knocking coming from the rear. Had the mechanic look it over, and he has narrowed it down to the suspension.

We have aftermarket dampers, and seemingly aftermarket springs (to lower the car).

With the car jacked up (suspension hanging) the springs have some (very minor) movement, which is the only loose thing on the rear so can but only be the cause of the knocking (especially as it only happens when going over a bump).

Can you get longer lowering springs (I guess longer but with closer coils)? These are not cut springs, so I have no idea what the US guy has done (other than potentially buy a set for a different car?).

Suggestions/thoughts appreciated. The rear does need to sit lower than standard to complete the look, but not hugely.

For reference, car sits this high currently:

 

[Aceman]

I'm wondering if I'd be best just replacing the lot with a set of the Tokico blues or similar..

 

[Alphabettispaghetti]

Possibly a dry or worn bush?

 

[Aceman]

Possibly a dry or worn bush?

That was my hope, but unfortunately all bushes are solid and accounted for, with no play (most are new polybush).

Exhaust is solid, all items removed from boot so can be nothing in there etc etc. It's bizaare as I would not have thought it was leaving the ground enough for the spring to move (weight of car compresses spring nicely, and as mentioned, only a very small movement in spring when rear of car raised and suspension hanging).

 

[rallymanDP]

Are there any Bump stops fitted ?

 

[morbias]

Are all the nuts on the top of the suspension turrets torqued up? Don't forget to check the one on the shock

 

[Alphabettispaghetti]

I had a bang at the end of mine, some idiot had cross threaded/misaligned the polybush so the pin couldn't move freely, this meant that the lower wishbone didn't have any free movement at the pivot point with the strut.

 

[Throttleton]

With the car jacked up (suspension hanging) the springs have some (very minor) movement

You may need helper springs, I think Francy may have some tips to check out for.

 

[Aceman]

Are there any Bump stops fitted ?

No idea. I'm not mechanically minded and so not sure what I'd be looking for sorry! Any pics?

Are all the nuts on the top of the suspension turrets torqued up? Don't forget to check the one on the shock

They were (well the three the strut brace connects to). Is there another I've missed?

I had a bang at the end of mine, some idiot had cross threaded/misaligned the polybush so the pin couldn't move freely, this meant that the lower wishbone didn't have any free movement at the pivot point with the strut.

Ok - so although new bushes, could be incorrectly fitted. I'll have a look and see what I can spot!

You may need helper springs, I think Francy may have some tips to check out for.

No idea what they are, but anything that helps sounds good to me! I'll start with bushes/strut bolts/bump stops (if I can find what I'm looking for) and if nothing then will look into "helper" springs!

 

[Throttleton]

Aceman, if you jack your car up and there is a bit of slack on the spring when the wheel is hanging down it is possible that when you go over bumps the spring will make a noise like you mentioned. I am no expert for sure just know a bit from our track 106 with helpers...
All the other points are valid and cost nothing to check which is good.....
Not sure if applicable but I bought aftermarket shocks for my gt4 and when I tightened the strut top nuts up up I found a little knock when going over bumps and found the threads did not go beneath the strut top. ie the the nuts had tightened onto the last thread of the shock but not up to the strut top.....

 

[Aceman]

I wonder then, as the front is fine on the aftermarket springs, but the rear has aftermarket shocks with the springs..

Oh well, I've a few hours next Mon I'll try and have a look, and if not, will see who's about at lakez if we make it for some diagnosis!

Cheers for suggestions!

 

[morbias]

They were (well the three the strut brace connects to). Is there another I've missed?

In the middle of the 3 nuts there is the nut that holds the shock to the strut top mount.

Something else to check is the big gland nut that holds the shock in the strut tube, you should be able to see it between the coils of the spring when the car is jacked up. It's possible one of them is not tightened up all the way which would allow the shock to move up and down inside the strut tube. Seeing as your car has aftermarket shocks on the back it seems more likely that it could be tightened up all the way and is bottoming out on the top of the strut tube instead of the top of the shock which would also let the shock move up and down, in which case you'd need a spacer between the shock and gland nut or even washers underneath the shock to raise it up. In other words you should be able to see a little bit of thread on the gland nut. Aftermarket shocks have different measurements from stock and need different length gland nuts depending on which ones you have.

 

[Rob Gaskin]

What happens if you try and bounce the car?

I'm thinking:

strut rod nut loose

Anti-roll bar (if fitted) loose

Diff strap broken (nose of diff).

Internal damper problem (had this on another car).

 

[jonbills]

any chance you've got MSA camber adjusting inner bushes?

 

[moggy240]

get someone to sit in the back of it and listen at each strut tower to narrow the noise down,could be a loose nut on the strut tube that holds the shocker in the strut tube.that was my problem when mine was knocking

 

[Ian Patmore]

Broken top mount.....?