Fluid change

What should I use? I'm doing the transmission, trnsfercase , front and rear differentials any advise? I'm thinkin syncromesh for transmission and transfer case and 85-90 synthetic for differentials sound good

Don't even bother, if the transmission is slipping, bring it to the dealer for service, if you get someone who does not know what they are doing you might as well just buy a new transmission now and put it on hold. If you have a manual, and it's not "grabbing" properly then you might want to take a look at the throwout bearing before you do anything else.

If you are set on the service though, Audi recommends (just throwing it out there) for a 2001 A4, with a 1.8L, synthetic 75w/90 gear oil, the part number is- G 005 000, for the diffs they recommend the same, and for the transfer case also the same. Just please don't go cheap, if you are going to do this, do it right and spend the money at Audi.

Oh dear! :s went Servicing Stop (http://servicingstopblog.co.uk) with my car the other day and spoke to them and they gave me abit more of an insight on this but need abit more help.