2008 Rear Axle Fluid...LS Additive?

[relentless85]

Looking in my owners manual on my 2008 Explorer 4x4 4.0L. The rear axle calls for 75W-140 synthetic oil but does not say anything about adding any limited slip additive. Walmart has 75W-140 valvoline that says it contains limited slip additive.

Is this ok to use since the manual doesn't specify that it needs LS additive? Or do I need to find the LS additive if I am replacing the rear end fluid?

 

[94Eddie]

If your Explorer is AWD then friction modifier isn't needed. Check to see if your differential is limited slip. Most Explorers don't have limited slip differentials and friction modifiers aren't needed for them.

 

[relentless85]

If your Explorer is AWD then friction modifier isn't needed. Check to see if your differential is limited slip. Most Explorers don't have limited slip differentials and friction modifiers aren't needed for them.

My explorer has the 4X4 low, high and auto buttons on the dash. It is not full time AWD.

The axle code listed on the driver side door sticker says "45", which I believe is a 3.55 gear ratio with an open rear end.

So, since that valvoline 75W-140 has LS additive premixed in with it already, do I need to find a 75W-140 that does NOT have LS additive pre mixed in with it? Or will the 75W-140 with LS additive pre mixed in work properly?

 

[Rcflyer330]

All 4th gen explorers have an open differential no LS additive is needed. If the fluid already has it added it should not cause any problems.

 

[94Eddie]

My explorer has the 4X4 low, high and auto buttons on the dash. It is not full time AWD.

The axle code listed on the driver side door sticker says "45", which I believe is a 3.55 gear ratio with an open rear end.

So, since that valvoline 75W-140 has LS additive premixed in with it already, do I need to find a 75W-140 that does NOT have LS additive pre mixed in with it? Or will the 75W-140 with LS additive pre mixed in work properly?

I would check the manual. I had the front and rear differential oil changed in my Mountaineer right after I bought it and used Ford brand synthetic. I don't remember the viscosity off the top of my head. Rcflyer is right. The 4th gens don't have positive trac. My 2002 Explorer did.

 

[Bill MacLeod]

This is the reason that friction modifier is NOT mentioned in the Owners Manual. No 4th gen had a trac-loc diff.

 

[relentless85]

This is the reason that friction modifier is NOT mentioned in the Owners Manual. No 4th gen had a trac-loc diff.

So, will the gear oil with LS additive pre mixed in do damage since my vehicle does NOT require LS additive?

there was a super tech brand that appears to not have LS additive ore mixed in, but I’d rather not use supertech.

 

[CDW6212R]

You can use either of those mentioned, the LS additive isn't needed, but it does no harm to have it if you have an open diff. The additive makes the fluid a little slicker to reduce clutch chatter, it won't hurt anything to have it.

I'd prefer the Valvoline over the off brands like store brands, generally buy the best available.

 

[96eb96]

So, will the gear oil with LS additive pre mixed in do damage since my vehicle does NOT require LS additive?

there was a super tech brand that appears to not have LS additive ore mixed in, but I’d rather not use supertech.

LS additive won't hurt or do anything in an open diff. You can even argue it may help things a bit because a friction modifier is kind of a sacrificial layer on the clutches. So it may give a tiny bit of metal protection, if anything.

 

[relentless85]

Next question, my manual calls for 80W-90 in the front diff. Will it damage anything if I change the front over to 75W-90 synthetic? I think I read other people doing that with no issues.

 

[96eb96]

Next question, my manual calls for 80W-90 in the front diff. Will it damage anything if I change the front over to 75W-90 synthetic? I think I read other people doing that with no issues.

Answer 1: It probably won't make a lick of difference. Your choice. May save a 1/10 of an MPG. If you live in a very cold area, you are starting out with a bit lower viscosity, which may have an advantage.
Answer 2: I have a AWD Lexus GS sedan that specs a very expensive gear oil for the rear end (75W85). The rear diff is pretty much exactly what the explorer has(an IRS setup). I think Ford is using(that gear oil) in their new trucks. Front diff specs what the Explorer does - Conventional 80W-90. What a Lexus master tech told me is gear weights are chosen based on the geometry of the gears (high offset pinion, etc). He said to strictly go by the book. I asked about using 75W90 in both diffs. He said it is not going to explode but I'm also not going to tell you to second guess Toyota engineers. I think the Amsoil site allows 75W90 for the Explorer, but they also sell a synthetic 80W90. I think climate would make the decision.

 

[Bill MacLeod]

75/90 is synthetic rated, 80/90 is not. By all means, use synthetic where possible. Brand is just a personal choice. Don't buy into the snake oil BS.

 

[96eb96]

75/90 is synthetic rated, 80/90 is not. By all means, use synthetic where possible. Brand is just a personal choice. Don't buy into the snake oil BS.

Amsoil makes 80W90 synthetic.

 

[CDW6212R]

Amsoil makes 80W90 synthetic.

They make three levels of the Severe Gear, the 90, 110, and the 140 top level. I've used the 110 in my front diffs, for my mail trucks for 15 years I guess. Long ago Aldive used the 110 in the rear diff, to help with fuel mileage. He figured it was so good that the 110 would be sufficient for his mild usage, his was the thread aiming for 30mpg, he had a SOHC 99ish model.