Vz[sv6] big thud when reversing??

[Svu6]

Heyhey i have an semi-auto(paddles) 2005 vz sv6, which is an awesome ride, but im constantly having this problem on many occasions when my car is reversing at a low speed it makes a loud "thud". As i keep reversing it "thuds" again. If i pick up the speed (when reversing) it doesnt thud.
Can someone please help me out and tell me whyy it is doing this and what should i do to fix it please?
All comments much appreciated
Thank you in advance

[Ghost]

Id be checking the oil first but the problem either lies within the gearbox or even the torque converter

[vz_sv6_owner1990]

Mate its more than likely you diff gears that need to be adjusted... Does it do it in drive aswell or just reverse

[Svu6]

It sometimes dies it in drive aswell. Pretty much everytime i come to a comeplete stop. Its just when reversing it seems to be louder/stronger.

Is replacing the diff gears costly?

[vz_sv6_owner1990]

You don't have to get them replaced. Just tell the diff place you want the backlash adjusted. And they will tighten it up and you will be sweet.

[richardpalinkas]

Or dif mount

[Danoz]

Or tailshaft CV.