Rear end oil change

[dvonwwe]

Planning to do differential oil change on 2001 Sport Trac. Calls for 80w90 oil. Would it damage differential gears if a heavier gear oil is used?

 

[drakeguy22]

it prolly wouldnt hurt but i would go with what it calls for.

 

[waskly]

or go with synthetic.

 

[drakeguy22]

i was gunna say that as well... i went with royal purple 80w90 in my 99 expo no complaints its also in the front diff

 

[2TimingTom]

Sure that's not the front diff fluid?

I thought the rear was much heavier.

 

[Clusterpup]

I run 85/140 in my rear diff because Aussie (I have one their lockers in my truck) says to use that weight in hotter temp environments. So in a nutshell you can use heavier oil. Nice to see someone else in Miami on this forum.

 

[bdmaash]

I thought all oils were supposed to be synthetic in this truck, for reduced drag thus improving mileage. Heavier oil is probably fine, but it will also increase drag.

 

[Blake A]

I think the rear end on all of them calls for synthetic. Mine did anyways. Front was normal though.

 

[Clusterpup]

The open diffs don't call for synthetic at least my Haynes manual didn't say that. I use a synthetic blend in mine. From what I recall, the limited slips can use full synthetic or conventional plus friction modifier additive.

 

[Lube]

From what I recall, the limited slips can use full synthetic or conventional plus friction modifier additive.

Even if it's a synthetic blend or a full synthetic oil, it will still require the friction modifier unless the oil container states that it already has it.

OP, no, running the higher viscosity oil won't hurt a thing. In a couple of aspects it will even be benficial to have an oil with a broader viscosity index (less prone to heat breakdown for one). You'll never notice the slight increase in drag caused by the increase in viscosity on your mileage if you use a synthetic.

 

[Clusterpup]

Even if it's a synthetic blend or a full synthetic oil, it will still require the friction modifier unless the oil container states that it already has it.

OP, no, running the higher viscosity oil won't hurt a thing. In a couple of aspects it will even be benficial to have an oil with a broader viscosity index (less prone to heat breakdown for one). You'll never notice the slight increase in drag caused by the increase in viscosity on your mileage if you use a synthetic.

Interesting. I could have sworn I read on a bottle of synth oil that it said it didnt need to have friction modifier with that fluid. Didn't give it much thought as mine is open, well, it was anyway.

 

[JohnnyO]

I believe the front takes 80w-90 and the rear takes 75w-140.