Hey ford experts first time topic poster.Ive got to say congrats on such an awesome website its nice to know that it isnt only ford new zealand that can be so unhelpfull. Im a first time to the v8 scene, Been a long time rotary buff so thought i will take up and drive something real nice i own a 2000 au xr8 cobra paid bugger all for it 3 & a half grand and only done 110 thou ks and is mint condition. My problem is that some times when you come to stop just before the car comes to a complete stop theres this loudish thud from the back and a slight push forward at the same time like someone slightly bumped into your bumper but only hapens on slow braking not hard braking.I have been to 2 ford dealerships and they dont know what it is and basically said its an au what do you expect even though ive spent nearly 3 grand in buying parts off the buggers to put the car on the road this is my only problem left its also an auto. Its pretty frustraiting and embarassing aswell when theres passengers.
Any help would be greatly apprieciated people dont like au's over here its a shame really they have there own charm lol.

Idle set too high or loose vacuum line? I know if you have the idle set too high on some autos they will kick down pretty harsh just before coming to a stop which sounds a bit like your problem. The loud sound might just be caused by backlash in the diff you might not notice otherwise.

Sound like the old Au diff las problem, according to Ford it doesn't exist. Buy yourself some decent diff oil and watch the problem disappear. I fixed mine by using Penrite Sin diff oil, nearly 3 years now and only a slight clunk, probably due for a change. If your really concerned go and see a local diff pro.
Cheers
Mr220kw

Is it IRS ?? In any case check suspension bushes etc
Yes idle control, check it idles down as should?
A good clean on ISC [idle speed control] may fix ..
Check uni joints, change diff oil as said..
Even an engine tune as in new plugs, leads etc can help..
Check hand brake is releasing? Or brakes for binding ??

Thanks for the massive response, Ive had diff oil changed and the ford additive put in it, New leads and spark plugs and coils 2 brake bleeds with new slotted rotors with bendix ultimate pads new wheel bearing's all round auto flushed out and new aftermarket cooler, Ecu reset and base idle set new air filter upper engine cleaner put through, Have had the rear bushes looked at and was told there fine but all the work was done by my local ford dealer and after paying a small fortune with them to get all that done they just dont want to know me, But are happy to charge a days labour looking i might have a look myself and see if anything's out of the ordinary or loose. it only happens now and then its wierd apart from that ford's rock. Last result i may take the advice and take it to a diff specialist everything is so big underneith it not like the rotor parts im used to lol, Oh by the way its irs to and cheers for the replys thats awesome.

It could be IRS bushes..Then ??
NOT suspension but the bushes holding diff to subframe..

Yeah last night i put it on the hoist and had my wife turn it on and drive it then stop and put it in reverse the diff moved heaps in the process so i might change them around and see if that makes a difference,Other than that a mate said it might be 1st gear clutch in the trans might be worn from previous owner doing donuts and wheel spins and has slightly worn it so when it gears down it jumps down to 1st instead of a smooth change, Which sounds pretty reasonable but it changes through the gear changes smooth as no worries so i will give the diff bushes a change and see how that goes cheers for the help man.