Rear Differential Fluid-- Conventional or Synthetic At This Point

[chris8428]

Morning,

After searching on this site and reading these threads along with one or two others:

Questions about differential fluid

Hi guys, I'm planning on change the rear differential fluid and i'd like to know which brand is the most reliable to use and how can I make sure I need to use the additive in a simple way. I've been reading lots of posts here on the forum so if you know one that explains all, please put the...

www.explorerforum.com

Changing Differential Fluids

Going to hopefully change the front and rear differential lube this weekend. My Hayne's has the rear needing about 1.5qts, but mentions nothing about the front differential. Can anyone guess as to how much fluid is in the front? Cornburner, you used 75W-140 in both right? Any real benefit...

www.explorerforum.com

I was going to change the rear differential fluid as I am probably overdue. I have 167,x.. on the car. I changed the rear diff fluid at 130,x.. miles but I cannot remember if I used synthetic or conventional. At this point does it make a difference? One of these thread states synthetic is called for in the rear differential. If it does have conventional and I go with synthetic do I risk leaks? I have the 3.55 open differential so I know I do not need a friction additive the limited slip models do.

Or, is this just one of those topic we tend to overthink and just getting it done is what is most important?

Chris

 

[chris8428]

I might have answered my own question. In looking at the housing it is clearly stamped "synthetic fluid" so I am 99% positive that would have been what I used.

 

[leadfootdriver]

The front is specked Dino, but the rear is Syn. There's a service pointer to add more fluid and fill from the top at the speed sensor..
If the rear diff takes 2.5 quarts, you add the rest of the last quart for a total of 3..
I used Amsoil 75/140. Even with the thicker oil, the original dirty oil ran quiet. The clean oil was noticeably louder for a while but has since gotten quiet..

 

[chris8428]

Thank you.