Odd drive noise...

Hi All,

Gradually working down the list of things to tick off on das hippo.

Next up, if I accelerate hard from a standing start while turning hard right I get a rotational noise coming into the cabin.

Coming from mid-rear of vehicle, it's a BRR-RR-RR-RR-RR-RR noise that's not hard contacting the chassis. Sounds like something vibrating rapidly around, like a shot CV joint noise but without the clicking.

Also the front left shock is currently knackered so it's leaning a bit more than it should when you fling it into a corner. (It never eeeeeends!)

Now I did notice while I was underneath doing the diff mount that the VCU bearings look a bit toast, but unless it's rapidly resonating around (entirely possible) I'm not sure this would cause it?

Possible candidates:
VCU Bearings
Wheel Bearing
CV Joints

Anyone come across this before?

Thoughts?

Handbrake cable rubbing on wheel?.

De-laminated brake shoe?

Remove the props and see if it goes away - will give you an indicator of what it can and can't be.

BTW, mine developed a noise that I thought was the rear of the exhaust fallen off a bracket - a mile later the IRD went big time!

Could be seized vcu causing rear wheel to jump to release wind up, do you have the biggest dia tyres on the rear?

freelance said:

Could be seized vcu causing rear wheel to jump to release wind up, do you have the biggest dia tyres on the rear?

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Identical brand new matched set of four tyres on!

Have you done the one wheel up test?

freelance said:

Have you done the one wheel up test?

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This ^^^^ One wheel up test is you friend

Guess this means I'm going to have to hunt down a replacement 32mm socket!

So doing some scientific measurement (read: d**king around) using a 1 meter bar on one of the wheel nuts...

Applying about 10KG of force makes the rear wheel turn 45 degrees in less than 30 seconds.

I don't think there's anything wrong with the VCU, which has only about 70k on it at the moment. Yes, I know that's coming up for replacement any time soon, but it seems okay for now.

Locking the gearbox in reverse so I could check the output shaft on the IRD shows that there's only about 2-3 degrees of play in the output shaft/backlash through the gearbox, which is naff all.

Grabbed the output shaft and tried to move it around, no dice, IRD output shaft is solid as a rock.

However, I can see the engine preloading badly on its bushings, may have to acquire the dreaded poly bushings for top and bottom to stop it bouncing around.

Is one of your new tyres at fault, oval, bulging or twisted? Personally I used to put a tyre lever through the uj s either side of vcu and make sure there was movement, but easier if on a ramp, but some peeps don, t like this approach.

freelance said:

Is one of your new tyres at fault, oval, bulging or twisted? Personally I used to put a tyre lever through the uj s either side of vcu and make sure there was movement, but easier if on a ramp, but some peeps don, t like this approach.

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In a straight line, up to 80 mph, hard cornering etc there's no vibration which I'd expect if the tyre was screwed.

I *did* notice a similar noise this morning though when I short shifted and the engine started to vibrate around. Not exactly the same noise, but similar.

I'm wondering if the VCU is thrashing about in its mounts.

B34R said:

In a straight line, up to 80 mph, hard cornering etc there's no vibration which I'd expect if the tyre was screwed.

I *did* notice a similar noise this morning though when I short shifted and the engine started to vibrate around. Not exactly the same noise, but similar.

I'm wondering if the VCU is thrashing about in its mounts.

Click to expand...

Definitely worth looking at the rubber VCU mounts. These deteriorate with age, not miles.
Inboard CV joints can stiffen up causing the bottom of the engine to flop about. This is normally a sign that the lower engine tie bar has gone slack.