Witch oil for 8.3/4

[cudaman-440]

I will change oil- 8.3/4 with "block" what kind -oil type i gonna use?
                                                                       

[Moparal]

I use 80-90 gear oil with a sure grip additive .

[Bullitt-]

Friend of mine who makes a study of these things says the synthetics are not as good in these applications. He said the synthetics don't cling as good as dead dinosaurs.

[Chryco Psycho]

not being an oil engineer it is hard to say what is best , the factory will not recommend synthetic as it was not availabe when the diffs & service manuals were made , most new vehicles recommend synthetics and the stresses are the same , to be safe use 80-90 dino , , I am running 75-90 syn in my diff though