Still Knocking

[RedCabbage]

As part of the rolling resto of my Chim I undertook a load of work on the rear end recently primarily to renew the diff bushes which were the biggest cause for concern and probably the biggest source of noises.

Having rebuilt everything I'm still left with one annoying knock from the rear. It is most noticeable at low speed over bumps, my first suspicion was ARB links so I've removed the lot to test it with no change.

To help narrow down the selection:-

It isn't the diff brackets they have been reinforced
It isn't the shock bushes because they are rose jointed Nitrons
It isn't the wheelnuts or wheel bearings

Suggestions what to check next are welcomed.

[T_Pot]

exhaust knock ?

[RedCabbage]

T_Pot said:

exhaust knock ?

Refitted all the mounts carefully as well, so unlikely.

[T_Pot]

have you checked the actual shocks? one could be fubard

[spend]

Are the springs still seated on the dampers under droop, if your car is low with stiffer springs they can clatter on the spring platforms. I think quite a few of us now have longer springs on the back with Nitrons (can't remember if they are 9 or 10" OTOMH)

Dave

ETA: Make sure you are not confusing the bumping/knocking with extending the drive shafts and drivetrain..

Edited by spend on Sunday 9th December 18:41

[RedCabbage]

The Nitrons are pretty new and seem to seat quite happily.

This particular knock has got progressively more frequent over the summer which suggests worn components somewhere.

[Rum Runner]

Fuel filter hitting the chassis tube , tank sender loose/wiring down rear quarter wing , Chassis to body bolts tight , handbrake cable knocking on lower wishbone if the cable ties have broken loose which hold it on the wishbone ,exhaust under tray bolts/rubbers , fuel pump rubbers worn or pump out of position and the little U shaped pipe which leads over the lower wishbone between the pump and tank ( remember the wishbone sits a lot closer when the car is on the floor).

Edited by Rum Runner on Monday 10th December 23:25

[RedCabbage]

I've just had another spannering up session to recheck all the torque settings and try to find my knocking. All looks and feels fine and to recap it is definitely not: -

Diff bushes
ARB/Links
Exhaust/Undertray
Handbrake cable
Fuel pump
Loose wheelnuts
Contents of the boot!
Diff mounting bracket
Propshaft UJs
DriveFlange bolts
Diff output/CV flange bolts

Edited by RedCabbage on Saturday 15th December 16:40

Edited by RedCabbage on Saturday 15th December 16:41

[T_Pot]

anything stored in the little cubby hole behind the seats ?

[spend]

Have you checked the drive shaft flange set crews are all torqued up, and the prop shaft U'Js seem to be a common clunker (TBH I would prob renew them when taking the prop off - assumed you did this when doing the rear diff bush). There have been a few reports of the rear diff bush mount failing? Worn CV joints seem to be reasonably common source of noise when approaching life expectancy.

Dave

[RedCabbage]

Previous post above edited to include the other items I checked.

Suspicion lies with: -

Wishbone bushes
CV's

If I place my hand on the parcel shelf behind the seats, the knock can be felt as though it has some weight/force behind it i.e. not a fuel filter more like a shock, wishbone or diff.

Edited by RedCabbage on Saturday 15th December 20:00

[T_Pot]

petrol tank lose?

sory im not a lot of help am i lol

[spend]

I found the best way to trace sounds was to get the back end up on ramps and get someone to bounce on the boot whilst I laid under the car. Subsequently you can get the chassis on stands and wiggle the wheels / get a pry bar on the bushes to check for worn joints/bushes. Its better really to go look rather than hoping to diagnose by guessing If its a case of it only does it when bouncing and moving it has to be the driveline? Its just a case of definitively isolating where the problem is really..

Dave

[RedCabbage]

spend said:

I found the best way to trace sounds was to get the back end up on ramps and get someone to bounce on the boot whilst I laid under the car.

Excellent! I'd forgotten that one.

It was on ramps today while I pryed, pulled and wiggled (the car!) trying to replicate the noise while someone else sat in the inside, but no joy. We'll try the jumping up and down in the boot tomorrow. Failing that it's going on my mate's 4 poster on monday for a better look.

Also I'll bite the bullet and order a wishbone polybush set, I was planning on doing the job in the spring along with a full geo set up but I need to eliminate this from the list of potential causes.

Shame, we were hoping to go to Scotland in it at Christmas.