Trailing arm knock

[Gavin Waddell 18]

Hello 

 

Bit of a weird one, i rebuilt my beam over the winter, i replaced all the seals and bearings (inner and outer), the shafts were in good condition and showed no signs of wear.

I've driven the car 1000 miles since and the passenger side trailing arm has developed a , i move the arm up and down in short movements it knocks. 

Took it all apart regreased and put it all back together and it still knocks. I checked the bearing and it spins freely and no wear on the shaft?

 

Could i have a knackered bearing already?

 

Thanks Gavin.

[jord294 91]

Did you remove trailing arm shafts and then press back in again?

[PhilNW 43]

Presumably the shock absorber is not connected

Edit - and antiroll bar not connected

 

When you "move" it do you mean you rotate the trailing arm on the axle bearings or move/rock the stub axle relative to the trailing arm?

 

 

Edited June 26, 2023 by PhilNW

[Gavin Waddell 18]

Jord: Trailing arm shafts where not changed, i pressed one 2mm to clearence for the arb seal, cant remeber which one.

 

Phil:  funny you should say that, i took every thing off this afternoon to check i hadn't messed up, with no shock and no ARB i didnt knock.

Put  on the shock and still no knock.

Put the ARB in tightened every thing and knock knock?

 

It knocks when i rottate about the bearing, i only move it about 1-2cm in short sharp movents. If i rotate it slowly nothing.

 

When im driving it seem to knock going  over small bumps but go over a speed hump where ther is a bit more suspension travel and it doesn't seen to do it.

 

Gavin

 

 

 

 

[PhilNW 43]

Hi Gavin

 

More questions..

 

When you rotate the arm does the knock happen with the trailing arm in the same position every time? 

 

Is there only one position where it knocks or more than one position?

 

Edit - are the torsion bars in place or have you removed them?

Edited June 26, 2023 by PhilNW

[Gavin Waddell 18]

So the with the car up on axel stands and no wheels it knocks at the beginning of the rotation? It doesnt seem to,knock further through its rotation.

The torsion bars are in place.

When the TB wasn't in place i dont think it knocked.

 

[jord294 91]

Bolts for arb levers tight in arms, and levers still a good interference fit on splines?

[Gavin Waddell 18]

Yep, i re tightened everything this afternoon,  the arb is an aftermarket 23mm. The thread in the end is a m6. End plates are a good fit.

 

[PhilNW 43]

Think you should remove TBs and confirm.

 

Think Jord is thinking of the bolts onto the arms at the end of the plate s

 

http://www.miamistu.co.uk/pug/GB/205N/5/51E01A.HTM

 

Item A

 

Are you thinking where they connect to the ARB itself?

 

Edit - How good are the ARB bushes ?  Item 5 on the same diagram above

Edited June 26, 2023 by PhilNW

[Gavin Waddell 18]

Yeah sorry ARB end plate bolts that go into the trailing arm are tight and there is no play in the plate and bar splines.

 

I will check to see if it knocks without the TB in place.

 

The seals are all brand new.

 

Do you guys think its ok to drive as i need to go to work 30 mile round trip?

[jord294 91]

Where the inner bearings a good interference fit when fitted? Did you fit them to correct depth? Any issue when sliding the n/s arm  into the bearings?

[welshpug 1,652]

So it only happens when the arb is fitted?

 

Sounds like poor spline machining on aftermarket arb.

 

Or the threads in the arm for the arb lever are worn, I have come across this a few times.

[Gavin Waddell 18]

Bearings were a good fit, i installed then using using a tool i machined to get them at the right depth. No issuses sliding the arm in goes in smoothly.

 

Ive had this beam for 15+ years and it never had any problems before , like i said i did 1000miles before it started knocking.

 

I will take out the anti roll bar and see if it knocks.

I will also flip the anti roll bar to see if the knocking goes to the other side.

I will measure the shaft and the bearing to see if they are a good fit

 

Any other ideas.

[Gavin Waddell 18]

These are the bearings i used

[PhilNW 43]

Is the 23mm ARB new or the original/previous? 

[Gavin Waddell 18]

The Arb is the original/previous one that i have always had in there, and it never knocked before.

One other thing a couple of weeks ago i could hear a rubing noise and the ARB end plate bolt had worked its way our and the plate also, i knocked the plate back in and retightened the bolt.

[Gavin Waddell 18]

Thats why i was thinkig the bearing was on its way out.

[PhilNW 43]

have you got one of the USB mini cams that you can have a look at the inner bearing to see if there is any damage?.

[pug_ham 244 3 Cars]

What car was the donor arb from, has it got one side of the end plates welded to a cut down arb?

 

11 hours ago, Gavin Waddell said:

I will also flip the anti roll bar to see if the knocking goes to the other side.

 

The arb should only be fitted one way, iirc there is usually a notch in the end for the left which should also line up the end plate securing bolt hole into the trailing arm if it's all aligned properly.

 

Did you tighten the rear shock bolts with the weight on the wheels / shocks compressed to the in use position?  I'd expect the bushes to twist but there's a slight possibility the centre bush spacer is twisting within the rear support arm.

 

g.

[Gavin Waddell 18]

The anti roll bar is an upgrade 205 one so no cutting and welding, cant remeber where i bought it from 

 

Good point on the shocks like an idoit i didn't tighten them up under load, rookie mistake.

[welshpug 1,652]

If The arb end plate bolt has worked loose its likely at least the bolt threads will be worn, try a new bolt with threadlock and a suitable washer.

 

The rear damper bushes are not bonded so whilst not ideal to tighten at full droop it wont wear anything out like you would with the front wishbone bushes.

[PhilNW 43]

Just a thought, might be worth disconnecting the shocks (giving greater movement) and get someone to bounce the car at the back and try and pin point the noise, as you think it might be ARB related.

Edited June 27, 2023 by PhilNW

[Gavin Waddell 18]

I will try all the above on friday to see, 1: remove shocks 

2: Remove ARB check for knock

3: Remove  TB check for knock 

4: Check for play in Arb end plate/splines.

5: Check bearings. Dont have a camera, unfortunately. 

 

I still reckon it's the outer bearing, thats picked up some play.

 

I might change the outer bearing for peace of mind, any one done it with the beam  in situ?

[welshpug 1,652]

On 6/26/2023 at 7:27 PM, Gavin Waddell said:

 i pressed one 2mm to clearence for the arb seal, cant remeber which one.

 

 

Put the ARB in tightened every thing and knock knock?

 

 

 

 

 

 

 

both trailing arm shafts should be inset 2mm, if they are flush there will be a bending force sideways on the arb end plate

[Gavin Waddell 18]

Update time:

Took everything apart again and it still knocks.

Reinstalled the TB = Still knockin

Reinstalled ARB = Still knocking.

 

I have a spare T/A shaft brand which i measured the diameter for the inner and outer bearing,  i then measured the shaft on the car, and they are both the same measurements.

I also had a spare inner bearing which i put onto the car shaft and no play checked it on my spare shaft and no play.

 

Outer bearing in the tube turns freely and has no play cant check the inner one unfortunately.

 

So i ordered a new set of bearings and will change the out might of had a dodgy one who knows . If that doesn't work i will change the TA shaft

 I cant quite remeber, but do i have to knock out outer bearing then the inner.

 

I will let you know how i get on.