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High Frequency Rear Vibration - Any Suggestions?


Mjit
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Hi,

Long story short I fitted a set of replacement drive shafts from Canley about 3 years ago, the ones they were doing with actual new shafts but had a no-warning hub bearing failure on the d/s on the motorway driving back from a holiday in France.  AA man had a look and seemed to know what he was doing identified a little wear in the d/s hub bearing but not enough to cause issue so fingered the diff.  Work has me away Mon-Fri at the moment so only had the following day to drop the diff before ordering a recon one to collect the following Sat.

 

Roll on 1 week and new diff fitted...and made no difference but I did spot huge movement in the drive shaft through the hub - and realized the AA man had jacked up under the chassis rail to test so shaft was running against rail, masking most of the wear when he was checking.  Would probably have spotted this with more time but file under shit happens and order a recon drive shaft for collection the following Sat.

 

Roll on another week, new shaft fitted and...fixed.

 

Roll on another week and had time to take the car for a 100 mile run and...I've picked up a high frequency vibration from the rear.  It feels like there's either a sex toy or mobile phone on permanent vibrate built in to the seat base above 50mph.  Towards the end of the journey started getting the tick-tick-tick of U/J death.

 

Roll on another week and re-greased the U/J on the d/s.  Fixed the tick for about 5 miles, so knew it was the new U/J on the new drive shaft.

 

Roll on another week and fitted a heavy duty U/J to the d/s.  Ticking gone but high frequency vibration still there above 50mph, so is it just a matter of time till that kills the new U/J too...?

 

 

 

Any thoughts as to the cause?  Googling suggests it could be a warped drive shaft flange but can't say I've spotted anything obvious while fitting and refitting the new shaft.  I do have a spare flange so can try swapping it - but don't get home till Friday evening and due be driving the Spit. from London to north Wales on Sat.  Probably time to try 1 thing, but only 1...

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This wasn't there before the diff/driveshaft swap and while I accept not impossible it seems unlikely that the vibration would only start when the new shaft went on and that, completely unreleated the new shaft would just happen to have a duff U/J that only lasted 100 miles.

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back to generalities,  drive shaft can have vibrations but at wheel rotational speeds   a buzz is more higher frequency so thats more propshaft as this runs at  speed  like 4 times as fast as the wheels so vibration is buzz whizz  rather than  whomp whomp

 

all drive flanges must be flat  run a file over them they do get bruised and this makes any coupling develop run out you dont want

 

somethings odd if UJ's  fail so quick even the worst should give you many thousands on miles 

 

make a check on exhaust fittings are not in body or chassis contact when the engines torque moves things to interfere when static it may be quite clear

 

Pete

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Exhaust could be a good call - 4-2-1-2 stainless system that's not caused any issues in the past but did come off and on to replace the diff. so has been disturbed.

 

Just so annoying being 300 odd miles from my car 5 days of the week so getting minimal time to investigate things :(

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Hello 

        Has your exhaust got the round silencer that sits between the chassis rails?

 

Because if it has there is very little clearance and its a bit of a B****r to get it to sit in the middle when the engine a gearbox move around(but worth it for the reduced noise but still fruity)but all the mounting straps need to be good not just look ok.

 

Just a thought you also NEED the gearbox mounting bracket or you do not stand a chance of keeping in central!

 

And it does make a noise if it touches(I know!)

 

Roger

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