ZX knocking noise under load/cornering - CV? Diff?

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Berd.S
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ZX knocking noise under load/cornering - CV? Diff?

Post by Berd.S »

Hi everyone,

I'm trying to diagnose the cause of a knocking noise on my '92 1.4 Carb ZX (105k miles on clock)...

The noise only seems to happen under load, on right hand turns. It can occasionally be heard on left handers faintly, but it never occurs off load. The noise is a rhythmic knocking, that appears to increase frequency with road speed. It's from the front of the car, most likely L/H corner. It also seems to happen in bump travel when going striahgt, although of course it's only momentary. Doing slow circles in a car park it's the same; no noise at low load at all, with rhythmic knocking on right handers under load (held back with the brake).

At first I thought it was an outer CV, although I'm starting to get concerned it's the diff as it only occurs under load, doesn't explain why it's so prominent only on right handers tho. In fact the whole one direction only thing has got me stumped, as the CV or diff are going to make the same noise in both directions surely?? . Perhaps it's an engine mount or suspension bush somewhere?

To test it I jacked up each side, started it, put it in gear and loaded up the spinning wheel with the brake. with wheels straight it rumbles and knocks, but would it do this anyway thru the diff which doesn't normally work this hard? On full lock, the LF makes the noise very loudly...

Thi problem has been going for probably 15k miles (I bought it never intending to do more than a years driving in it while I got my other project car on the road, however...'ve now got attached!) without the symptoms getting too much worse...I've noticed I've also got a leak from the gearbox, so perhaps I'm out of oil also... :oops:

Anyway, I'm new to this forum as you may see, looks like a really useful place for info (I did try a search before posting but no luck...). Thanks for your help in advance, can anybody shed any light on this, or had it happen before?

Thanks,

Al
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Post by jgra1 »

hi Al and welcome,

one possible cause is the inner driveshaft tri-ax joint..
very doubtful its the diff..

as you say, other possible culprits are lower arm front and rear bushes, cv joint, engine mountings..

others will be along shortly with more help :D

John
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Post by Peter.N. »

I would go for the CV joints first.
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Post by RichardW »

ISTR that the MA gearbox fitted to the 1.4 variants of many PSA cars is a bit weak in the diff bearings department, and the symptoms you have got are certainly sugegstive of diff failure.... :cry: Try a google search on pug 306 1.4 gearbox failure and see what comes up.....
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Berd.S
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Post by Berd.S »

Thanks for your replies so far guys. I think I'm going to crack on with both driveshafts - they both appear to have a small amount of radial play and a slight bend in both. The car has recently failed its MOT so It's up on stands anyway...There's some receipts for CV boots in the history so perhaps some crap got in there at some point and wasn't fished back out again...
I feel the work on this car snowballing already...:(
Does anybody have any words of wisdom for me on changing these shafts? I'm thinking of going with GSF for parts. Should I change the RH support bearing as a matter of course? The shafts should come with both the CV and the Tri-ax joints correct? (sounds like a silly question...but the new front dampers I just bought from GSF didn't even come with dust covers or bump stops! X-( )
If it's the diff I may break down in tears...Is a gearbox swap an involved task? TBH I've only ever done front engine -RWD gearbox swaps before...I just need to keep in mind this was a cheap car that doesn't like to start and occasionally wafts blue smoke around you when it does finally start!...
Thanks very much!
Al
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Berd.S
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Post by Berd.S »

Hi Guys,

Just to polish this one off, Changing both driveshafts did the trick on this one, had myself convinced it was the diff too!

New shocks all round, 2 new rear wheel bearings, freed rear adjusters, 2 new driveshafts, gearbox oil change and an MOT retest later and the ZX is alive for another year!

hurrah!

Al
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