GQ rear diff dilemma!!!!!!!

[Zonka]

G'day all,

I removed both diff centers out of my Mav with the intentions of getting some brand new 4.6's installed. I have no idea how set-up 'back lash' etc so I took my centers down to the local ARB shop. The guys were more than helpful & said they'd install the gears for me. I received a call a couple days later advising me the pinion bearing was pitted and that it would be best to replace all the bearings. This blew my budget out a bit but considering the bearings had lasted 20yrs getting them done would ensure another 20yrs trouble free driving.
After parting with my hard earn cash I finally got the centers back in only to have this extremely loud rumble fill the cab when going 50km & above. If I back off the throttle the noise goes but just slight pressure & BAM it's back. Increase in speed & the noise only increases in pitch.
I called the chap who supplied the gears and he's positive that the gears he supplied are not at fault & that ARB have stuffed up. I have called ARB and they want to test drive the car but I'm afraid they going to put it back onto the gears. Secondly, I just spent a quite a number of days re-fitting the centers which isn't easy lying on the floor! Would it be un-reasonable of me to ask ARB to remove the diff center & check their work at their expense?
I paid good cash to avoid this exact scenario but here I am!!!! Sorry for the rant but any advise would be appreciated

[love ke70]

let them test drive it and go from there.

you havnt still got the front hubs locked in do you?

did you put the rear drive shaft on the right way? assuming you marked it before removal?

if not try turning it, could be upsetting its balance..

[coxy321]

Sounds like either tailshaft/uni noise, or they've done a sh1t job setting the mesh on the CW&P. An easy way to check would be to pull the rear centre out and check their proofing marks, presuming they did actually proof it before assembly.

[Zonka]

UPDATE!!!

Cars at ARB. Took one of the mechanics for a test drive and he's positive it's the diff.
They're going to strip it back & see where it has gone wrong. When coasting to a stop you can hear the gears meshing quite clearly.
Should hopefully get some news tomorrow, fingers crossed!

[purplebus]

is there any oil in it.??? sounds silly but I have been found guilty before but only backing out of shed.
good cust relations from arb so far. keep us posted.

[Zonka]

No oil would be kinda funny but no, plenty of oil!
Prior to diff rebuild car was quite ie no uni noise etc hence why it was fairly easy to pick.
The guys at ARB have been fantastic! Just hope it's something trivial.

[Zonka]

Well it's definitely been an interesting 3 weeks since the last post.
The blokes at ARB have been GREAT!!!! To date they've removed the center out of the car at least 6 times, replaced the bearing (3 times) & replaced the gear set (TWICE!!!) yet the noise still persists. After much head scratching and swearing it turns out the current batch of after market 4.625 ratios that came into AUS are faulty!!!
I've given up! I'm ordering a genuine set of gears from Nissan. Knowing my luck these will rumble as well!!!!