SLROC Forum

Hello,
 
  I had pretty heavy vibration in my defender a couple of weeks ago that I traced back to worn out UJ's in both my propshafts (all four completely dry and one literally in pieces!).  I've now fitted brad new, virgin propshafts front and back, and although the vibration they were causing has gone, there's still a vibration bad enough to blur my door mirrors that comes in under torque between 45mph and 60mph.

  I'm suspecting a worn diff - possibly the back, as it has quite a bit of backlash in it - but does this sound likely?  Is there a way to diagnose the state of a diff?  Diagnosing the propshafts was easy, as I just took them off and drove about to see what difference it made...a bit trickier to do with an axle ...

  Any thoughts welcome...

-mudTerrain

Did you check the grub screw on the handbrake drum before refitting the prop shaft? If this isn't tight, the the prop shaft won't bolt up correctly and will cause vibrations.

I didn't actually check it - I didn't think to - but the propshaft bolted tight to the handbrake drum, so I assume the screw wasn't loose/in the way...I'll certainly go back under and check, though - thanks for that!

Have you got a lift on ?

Are the yolks on the props lined up correct

Not 100% sure but the yokes sould be out of phase. I think

Fronts 45 out normally

Rear in line from factory but best offset for articulation if that is you bag

Thanks for your replies...

I fitted entire new prop-shafts front and back, so the UJs were already fitted (by terrafirma) - I didn't think I needed to align the front and back propshafts to each other, as I imagined they'd go out of phase with each other just through normal driving...

I haven't got any lift, but it is a special vehicles ex-electric board defender with dual rear springs, so it's slightly higher than standard...

...and here was me thinking "it's just sixteen bolts, how hard can it be?" 

Thanks for your help.

your rear diff will have lots of backlash thats fairly normal on the heavy diff , have a look at gearbox and engine mounts check one of the rubbers hasnt split, particularly the gearbox ones that would allow the transmission to move, also worth swapping wheels front to back to check its not a deformed tyre, bent rim etc

first thing i would do to isolate the UJs and DIFFS would be pull off the front drive shaft and stick it in diff lock and go for a drive.

IME the front prop is the bugger that causes vibrations due to the angle is usually at.

but like piper says check the wheels and the gear box for play.

let me guess it was the gear box end of the front prop that had fully disintigrated ?

Thanks for your replies...

Would a bent/out of balance wheel only vibrate under acceleration?  I would have thought it would vibrate all the time...I'll check them, though.  Gearbox/engine mounts was my first guess before I diagnosed and replaced the propshafts - I looked at them then, but they weren't obviously split/damaged...is there something more subtle I should be looking for?

Thanks for the info on my rear-diff backlash...that's always been a bit of a worry

I've been driving about in diff-lock without a front propshaft for the last week, waiting for it to turn up in the post...the vibration was still there, so it's definitely one of the axles/diffs or the new propshaft.  The disintegrated UJ was the handbrake end of the rear shaft, oddly enough...

Thanks for your help,

-mudTerrain

Is it a TD5 with the loverly dual mass flywheel...................................................

There's a happy thought 

From what I've read about failing dual-mass flywheels, there's usually more rattling/mechanical noise associated with it - I'm getting none of that, so I'm going to stick my neck out and say it's more likely to be something else...

(watch this space for an "I'm fitting a new flywheel" post...)