PCM mod (hypertech vs mopar)

From : werlax

Q: friends i have a 1996 pu 1500 v8 5.9l snow plow and tow package with the lsd and need to change the gear oil in the rear actually front too. i know these types of questions have been asked before but i want to make sure im doing it right and implore on your tolerance. is 80w 90 okay for the rear as i have some on hand i bought a bottle of the friction modifier from the dealer and its 4oz. it says to add 2 to 5% based on the gear lubricant weight terrible in math i am. on an earlier post someone stated to add 8oz. is this what my truck needs or is 4oz right what type of differentials do i have are they dana 44 and 9 1/4 for front/rear in the owners manual it says the fluid level for the front should be 1/4 inch below the plug and 5/8 below the plug on the back if i have the above differentials right. does it really need to be that exact on an unrelated note do i have the 231 transfercase im changing that fluid as well. thanks very much all. steve .