Im getting ready to change the oil in the rear end and i have heard you should use some kind of additive. Does anyone know the name of it ? Also what gear oil weight should i use ?

 

Don't know the name, but I got it from ford when I broke my axle in the harley.



Me getting done putting the axle in. 6 months later went back in,(long story) and I didn't put it back in that time that was over 4 yrs ago. I know I should have but It wasn't available for me at the time.

Now my weekend job is at oreillys for the dicount and they have the additive there, never used it but I guess it's the same, might want to look into it. It's gotta be better than not using any at all I guess

 

The rear diff should be tagged with the proper oil, more than likely 75w-140 synthetic if it is a limited slip. You can go to any auto place and pick up the limited slip additive, thats all its called. Most manufacturers already have the limited slip additive in it but be sure to read the bottle before hand. I believe you only need approx 4 oz. of additive too.

 

I put 85W-140 Valvoline Semi-Syn in my 2001 (tag states 75W-140 fully synthetic, but I am not spending that kind of cash on expenzive oil for nothing)

Valvoline Semi Syn 85W-140 costs about 5-6 bucks a quart vs. the 15-20 qt for the 75W-140 full syn. I took a chance, but as I figured...nothing would come about of it (using an oil NOT stated on my tag on the diff) but some savings which I bought some beer and BBQ supplies with when I was done

I am not saying to do this ( oh no....never deviate from the factory weight oil ha ha).....but in all honesty my truck has had that oil in there for about a year and looks great, no chattering form the LS clutches....and I added a tube of limited slip friction modifier from the local parts house (4-5 bucks). If there is anything special about the rear-ends on these new trucks, I have not found it because they look the same inside as any of the other older ford rear ends that I have had the plate off of, nothing different. Some Ford "factory certified" technician on here will correct me.... but regular 85W-140 semi synthetic oil worked fine in my truck

Hope that helps

 

i did spend the $18 a quart but I didn't put an additive in should I have or did the fluid already have it?

 

I did the same thing as JJ and like I said 4 years later, nothing wrong with it except for the seal that was screwed up when I put it in. I didn't even use semi-senthetic, don't remember what weight I used, I doubt it was right. haha

 

I'm running Valvoline 75W-140 synthetic, mainly because I work there and it's free.

 

I want a job

 

lol...if it wasn't fully synthetic, then it damn sure wasn't 75W140

Man, like you said, it works great with "conventional oil" in it, and I felt just as good about putting in a cheaper oil after I got thru with the beer and BBQ

I actually read that the synthetic oil doesn't rectract heat off of the gears as well as regular oil, thats why some diff manufatcures will void the warranty is synthetic is used (cannot remember, seems like it was Currie or Eaton). Like I said, I just read that....don't know the merits of the story though.

 

I am pretty sure its Friction Modifier that your taking about and you only need it if you have a limited slip Ford rear.