Holden sv6 diff problem?

Have searched the board but can't find an answer. At low speeds I get a bit of a clunk coming from - I believe - the diff. Mate told me to just stop going slow. lol. Would that signify a diff problem? Is it a big fix? Have looked on a holden message board and apparently a bit of diff noise can be normal in the vz, but obviously don't want it seizing on me. Occasionally on start up the check drive train message will come up but only rarely. I apologize if this is a silly question!

Nobody is going to be able to tell you what's wrong or give you cost estimates until its been physically checked. The check powertrain message after startup means that a non emission related fault code has been logged in the engine control module. Best see a Holden dealer.

All I can think of off my head is a drive line uni or the collapsible crush spacer in the diff head input lost its crush factor and has released some preload off the pinion /crown-head mesh due to use of old or incorrect oils used in the diff like mineral oils instead of a synthetic.Im not sure if the sv6 hsa drive- line centre- bearing worth checking too.
All wild guessing of course ;-) but those things need checking of course transmission is the next best check.& or worn rear suspension components resulting from chch bad roads!
Take it to the dealership. w/shop

Thank you both for your replies, much appreciated. I like to at least have some idea as I find sometimes being a female with little mechanic knowledge one can be taken for a ride as it were.

My SV6 was clunking like the lsd was grabbing but I only noticed it at a really slow speed when turning slightly or reversing straight. I talked to the local Holden forman and he said it was common. Easy fix.but not cheap. Go to holden dealer and get 100ml of Friction Modifying Additive for IRS LSD Chatter Fix. Its from Spicer Australia and it has a really powerful smell for about $80 but that may be the trade price. Buy 2 litres of fully synthetic diff oil to suit VZ commodore. Drain the diff oil, add the 100mls of additive then top up the rest with the new diff oil. I think I used a Castrol synthetic diff oil but I can not check. I have the $80 additive bottle in front of me. Holden will tell you it will take about 30 km of driving before the noises disappear but my diff was back to silent within 6 km. You could try just replacing the diff oil with fully synthetic oil as it did say on the container that the oil was designed to stop LSD chatter. Its only a half hour job if you have the tools and a pit or hoist etc.

I remember my Holden Berlina V6 bought new in 1995 had a clunk in the diff. Despite several visits to Holden dealer and a visit from Holden NZ tech guy I was assured it was not a fault, just "tolerance stack-up". In other words typical Holden crap quality control. After numerous other issues including engine out twice under warranty for oil leaks, it was sold at 3 years old. What a piece of crap.

I saw a car once that the head mechanic of the dealership was trying to find the fault with, with the same symptoms as you described.
Had it on the hoist, everything tight in the suspension, diff mounts etc.
I walked up and asked if the fact that the car was missing 3 out of 5 wheel nuts on one of the rear wheels could be causing it. Sure enough!
One very red faced mechanic.