I just installed a 3.5 w/ vlsd in my 5at. But the place i got it installed only had 80w-90 gear oil as oppose to the 75w-90 gear oil that everybody usually puts in their differential. He told me it should be fine,so i told him to put it in anyway. I was wondering if theres any difference?? and should i switch back to 75w-90 gear oil? The car seems to run fine right now, only had it on for 2 days so far. Also what are the negative effects of putting in 80w90 as oppose to 75w90 if there is any???Any feed back will be appreciated. Thank You.

 

it will be fine

 

so how do u like it? I sort of have mix feelings about mine.

 

I just replaced mine with mobil 1 75w-90 and an additional friction modifier (wasn't the usual Ford stuff that I use)... works great

 

Yea i sorta have mix feelings about mine too. I raced my friend's g35 who has intake and exhaust, while i have intake and headers. So basically same mods, except that i have a 3.5 differential and he doesn't. We both drive a g35 5at. And to make it even more accurate we agreed to not brake torque, just floor the gas and thats it. And i clearly felt the 3.5 FD helped me accelerate faster but his car was also clearly faster in the topend. Once we reach speeds past 100mph, his car would start to pull on mine. In 1st and 2nd gear my car would pull on his though. So i dont kno, its sort of liek a trade off of being faster at lower speeds vs higher speed.