Hello all,
I recently installed motive 4.10 ring and pinion gear in my 2009 f150. I kept the stock spider gear unit. The instructions that came with my motive kid recommend i use a 80w90 gear oil but when I read the truck manual it recommends 75w140. What do yall think I should use? BTW been driving it now for about 5,000 miles since the swap with 75w140 with no issues but am about to drain and fill the oil which is why I'm asking.

 

If it were me, I'd look at the oil before deciding. If there seems to be excessive wear, id highly consider switching. If it all seems good, I'd rock what you have been. At some point lubrication is lubrication. I'm guessing it would all be fine after only 5k.

You may want to call the manufacturer and talk about it with them. Although you may want to leave out details on how you've been running their product without the suggested gear oil for 5k miles. lol