Oh yea you should be using GL4 rated oil, and the correct weight should be, 75w90 not the higher 90w140 crap. its far far to thick for our transmissions and puts an extra pressure load that is not needed... unless of course you are using it for solely track racing purposes.

Always go with the OEM recomended. That is 75w90. Trust me on this. It might run you 20-25 a quart, but you only need 2.1 quarts.. not bad for 50 bucks... or 600-2000 for a new trans.