thumping and slight grinding noise rear end

[bnghardy]

Need some info??
My ride is a vxii 6cly auto. when I reverse out of the drive way or car park the car vibrates (grinding noise) to a thumping noise from the rear end only
very lightly or not real loud and only when it's going in reverse. could it be the rubber uni joint (yoke)on the tail shaft.
but before you answer it went to Sydney last week from Brisbane there was shuddering ( misfiring) every time I accelerated to over take or to go up hills. when I got to Sydney looked at the spark plug leads and found one was corroded at the coil pac so replace them and it fixed that problem. So what I'm getting at would all the misfiring cause the rubber (yoke) uni to weaken up the rubber to cause this thumping and grinding at the rear end when reversing. and can I check it like you do a normal uni joint. or is it my rear brakes need changing
any ideas welcomed.

[bricat]

I have vt2 calais and have similar noises from diff. I am led to believe it is the gears just meshing and normal. Just to be on the safe side check the oil level in diff.

[Cashman_309]

Vibration at very low speed could be engine mount, trans mount, diff mount, tailshaft doughnut, uni joint, diff gears.. the list goes on..

Only one way to find out. Get the car on jack stands and start rotating everything by hand and checking for grinding and sloppyness. Start with the rear wheels, tail shaft, if you suspect the tailshaft, unbolt it from the diff and turn the diff just in case its actually backlash.

[Not_An_Abba_Fan]

Reverse the car a bit then stop it and get and look at the rear wheels, if you have really bad camber on one of them it will be a cracked rear diff cradle.

[bnghardy]

thanks guys
'll check it out. forgot to mention the car is x cops car and has a LSD rear end would that change a few things on finding this problem.and I will check the diff oil as well.
a cracked rear diff cradle I thought they (holden) fixed it on the vx by strengthening the rear cradles up I'll have look anyway.
Cheers.

[umair]

If you hit reverse and it goes like grrrrrr and vibrates it your mounts.

[bnghardy]

Hi umair: do you mean the rear K frame mounting points.(diff housing)