Driveshaft (axle) knock??

[villn808]

So my bad luck with the diff in my VF continues.

Ever since installing new Truetrac there has been a knock coming from the diff area of the car, a deep knock that gets faster with road speed. But strangely goes away after about 20 mins of driving.

Just had the car back to diff builder, who is trying to tell me that it’s due to the car being too low, and driveshaft (passenger side he thinks) inside the housing is knocking somewhere.

Even though the previous Truetrac, that was in the car for 3 years never made this noise And height hasn’t changed, although did eventually develop a whine and start leaking, reason I changed it.

The noise is really bad when cold. And I know of several other VE/VFs with Truetracs at similar height with no dramas.

To me if it was due to height how would it go away when hot?

Any thoughts or advice appreciated.

 

[mechanic]

Need more info.
Does it knock with tyre rotational speed, or driveshaft speed?
Does the knock severity change under acceleration, when coasting or deceleration?
What about when turning corners?

Jack it up at the back, take the rear wheels off and drive it up to speed. See if the knock is still there.

 

[villn808]

Need more info.
Does it knock with tyre rotational speed, or driveshaft speed?
Does the knock severity change under acceleration, when coasting or deceleration?
What about when turning corners?

Jack it up at the back, take the rear wheels off and drive it up to speed. See if the knock is still there.

As far as I can hear it, it’s noticeable only under light acceleration.

You do hear it while tuning corners while accelerating.

I don’t understand the difference between tyre speed and driveshaft speed, aren’t they the same?

 

[villn808]

Also if I was to drive it jacked up with wheels off wouldn’t the brake disc unbalance and loosen? Pretty sure the wheel nuts don’t have enough thread to tighten up with wheel off.

 

[BlackVXGTS]

Also if I was to drive it jacked up with wheels off wouldn’t the brake disc unbalance and loosen? Pretty sure the wheel nuts don’t have enough thread to tighten up with wheel off.

Yes, you need to buy some "hollow" wheel nuts to keep the rotors on the hubs. Can get them at Supercheap and others.

 

[MattSAU2XR8]

Or use some large sockets with the wheelnuts inside them to hold the discs on - 3 each side might do it

 

[Milo 6.0]

If one of the driveshafts is hitting something it wont be hard to see the damage/marks left on the driveshaft by that contact while being driven,some tru tracs can be clunky according to the diff place who installed my tru trac copy in my falcon,not totally common but it has happened,i also recall a few guys when i was on the ford forum removing tru tracs because they got sick of the constant clunking according to them,very strange that you had no issues before but now you do?
I had an eaton tru trac in my g6e turbo and it was whisper quiet so im definitely not a hater of said traction helpers
Maybe the diff place fucked up the install and are washing their hands of it,go to another diff place and get them to check.
Btw the old tru trac wouldnt have been worn out it would have been the pinion or carrier bearings whining,tru tracs dont wear out,if they let go they just break from what ive read/been told.

 

[villn808]

So diff builder was really good and ended up building another diff with a new Harrop Truetrac I supplied, even though he was pretty sure the diff wasn’t the problem.

And it wasn’t. Clunk still there taking off, worse if anything. Even raised the car 20mm, as he thought was the issue, but still does it. Splines on shafts perfect, no signs of knocking inside the diff anywhere.

We’ve come to the conclusion after checking everything more than once, than I have somehow damaged one of the CVs on the shaft taking old diff out and new one in, no idea how.

So have new pair on the way and fingers ******* crossed.

 

[villn808]

Found set of shafts from VF2 redline with 28,000kms that was scrapped due to water damage. They go in tomorrow. Before they do I thought I'd get a video of the damaged one. Got me stumped how I didn't have the noise before I took the old diff out, and had it after? Did I damage one of the CV's taking diff out? Can't see how I would've, was pretty careful. Also the wheel on same side had a slight buckle, that's been fixed too.

 

[Immortality]

Is it the inner or outer CV that is damaged?

I always tie up the axle shafts when pulling out the diff where some people just let em hang which may not be good for the CV's.