So ive asked around and it seems that Motul Gear 300 75w90 is what can be used with the z transmission and diff.. (i had redline fluid in it before this) so i went to a shop by my house that sells motul fluids thinking theres only the gear 300 100% synthetic 75w90 available.. instead i bought the Motul Motylgear 75w90 thinking it was the same thing wich turns out its not.. Motylgear is semi synthetic.. Gear 300 is 100% synthetic.. both are gl4 gl5.. the reason i changed it was because in the morning it would be noisy and grind from first to second ocassionally.. and seeing how the stock fluids for the trans and diff are non synthetic.. now i figure semi synthetic is the way to go.. and so far it works freakin awesome.. its smooth, quiet and less occasional morning grind.. i havent tried the gear 300 on it yet but i like to try diffrent fluids so as soon as i do ill post it up.. hope this helped in some way..

 

Be weary of any fluid that is rated GL5. GL5 lubricants have extra additives which are corrosive to yellow metals (bronze synchro's like the ones found in our transmissions)

If you search you'll find a ton of info on this

 

if it is gl4 gl5 MIL-L-2105D then it will not harm the synchros.. ONLY gl5 has that "extra additive" is a high level of sulphur/phosphorus wich does corrode copper/bronze.. as long as it says gl4 gl5 you'll be okay.. its the gl5 only that will harm our trans.. and even then there are alot of different opinions about this with vw..mb..and bmw owners since there trans also specify gl4 only.. you'll learn alot if you search this subject extensively..

sherif from forged performance also recommends motul 300v 75w90
z store techs also recommend the motul 300v/technosynthese 75w90