colorado problem again and again

There should be a crush washer behind the drain and filler plugs - I would suspect that if the diff was over pressurising, the oil would seep past the axle or pinion seals before it crept past the plug seals... If they changed the diff oil and didn't replace the crush washer, the oil would almost certainly seep out regardless of diff pressure...

Shaneo86, I dont think its realy Holden crap more like you have managed to find crap mechanics @ service manager.

If you have had so many problems with the dealers why do you persist on fart arsing around with them? go to holden themselves and complain. my mate used to work at fishermans bend in engineering, he used to see the cars that dealers took back due to ongoing issues of many varieties and various models ( he also used to get flown interstate to identify and rectify electrical problems when the dealer couldnt ). go to your states GMH armed with all of the invoices and correspondence you have had with the dealers. if they deem it enough of a problem and you bought it new they should do something. they may give you another vehicle- BUT have you done any mods to it or is it standard. if it is modified in any way it may be all in vain. they more than likely wont want to know you ( been there, done that so i know first hand ) this would be the way i would now attack it.

now shaneo86 you sure you weren't caught fixing up the managers wife from the dealership you brought your Colorado from !!!!!!!!

I have had 2 Nissans & 5 Toyotas & have only ever had 1 (yes thats right,one) scheduled vehicle serevice at any dealer. I use them to buy vehicles & for any warranty claims & that is it.
Do yourself a favour & form a working relationship with a good mechanic. Most mechanics can remain in business for decades on the back of the quality service they provide. A good mechanic would have you fixed up without hesitation.
Dealerships workshops rely on the fear new car buyers have of loosing warranty if they go elsewhere.
After having a blue with a dealer after they stuffed up a warranty work I paid a mechanic to do what should have been done in the first place.

why would they seal the breathers?

If you have followed this long running saga you would have read that the

dealer sealed it all up to see what was happening to the oil.

What then happened was it blew a lot of seals.

This must be the biggest lemon of all time.

About 17 years ago I worked at Zupps holden at Mt Gravatt as a mechanic.
I have worked at a fair few dealerships and found Zupps to be a very good workshop and run really well, however this was a long time ago so things obviously must have changed.

You will find dodgy mechanics everywhere not just at dealerships like some have mentioned above.....a lot of good mechanics come from dealers.
Out of maybe 15 mechanics at a dealer you unfortunately dont get to pick who works on your car that is the worst thing about them.
The only thing you can do is keep trying different mechanics outside of dealers until you find someone your happy with or go by someone else's word of mouth.

It definitely seems like you got a lemon though!