Hey, all, I have a 1986 F-150 with the 4-speed, cast iron NP435 and the Ford 9" rear end. This truck is kind of ran hard, and is used to haul wood and even a car or two now and then. Also, it gets taken off road a LOT for play, and to go out into woods and load up with wood. It's a mountain goat, that's for sure.
Well, I've switched the 302 in it over to Rotella 5W-40. The rear end has whatever came in it, more than likely (120k miles), and the NP435 has M1 75W-90 (GL-5). After I switched to that, I then started to do research and found out that GL-5 is not what you want for older transmissions. My truck has done fine with it, but it does very poor now that temperatures are cold. And, all in all, I don't feel like it's the right stuff for my truck.
I did the same to my wife's Eclipse, all around the same time, and her shifting started out better, then noticeably got worse and worse, so we switched her's to Redline MT-90. HUGE increase in smooth shifting. Now, that is what I want to put in my transmission (it specs an 80W-90). And I do want to stay synthetic, because when I put the Mobil1 75W-90 in there, my gas mileage improved dramatically. Don't know by how much, I just noticed that the gas hand didn't move nearly as fast while going on the highway (2300RPM @ 55mph = bad mileage no matter what for this old V8).
So, are there any disagreements about MT90 for the NP435? Also, like I said, I want to change the fluid in my 9" rear. I want to use a 75W-140 for it, but don't really know what brand to go with. I was more than likely going to go with Redline, because the MT90 did so well for me, but does anyone else have any recommendations for a good rear end gear oil? Thanks for any advice given.
Well, I've switched the 302 in it over to Rotella 5W-40. The rear end has whatever came in it, more than likely (120k miles), and the NP435 has M1 75W-90 (GL-5). After I switched to that, I then started to do research and found out that GL-5 is not what you want for older transmissions. My truck has done fine with it, but it does very poor now that temperatures are cold. And, all in all, I don't feel like it's the right stuff for my truck.
I did the same to my wife's Eclipse, all around the same time, and her shifting started out better, then noticeably got worse and worse, so we switched her's to Redline MT-90. HUGE increase in smooth shifting. Now, that is what I want to put in my transmission (it specs an 80W-90). And I do want to stay synthetic, because when I put the Mobil1 75W-90 in there, my gas mileage improved dramatically. Don't know by how much, I just noticed that the gas hand didn't move nearly as fast while going on the highway (2300RPM @ 55mph = bad mileage no matter what for this old V8).
So, are there any disagreements about MT90 for the NP435? Also, like I said, I want to change the fluid in my 9" rear. I want to use a 75W-140 for it, but don't really know what brand to go with. I was more than likely going to go with Redline, because the MT90 did so well for me, but does anyone else have any recommendations for a good rear end gear oil? Thanks for any advice given.
