Which grade of oil do I use in a rear axle differential?

[mikecarp]

I have an open differential (non-LSD)- owners manual call for 80w90 but i notice in many explorer threads that 75w140 is being used even in the open differentials. Is this advisable? By the way, I'm changing the oil to try to eliminate rear end noise.

Thanks

 

[BrooklynBay]

Welcome to this forum! I've renamed your thread, and moved it into the transmissions, transfer cases, and differentials section. I don't think that it's a problem using a heavier grade of oil.

 

[gavin]

I have an open differential (non-LSD)- owners manual call for 80w90 but i notice in many explorer threads that 75w140 is being used even in the open differentials. Is this advisable? By the way, I'm changing the oil to try to eliminate rear end noise.

Thanks

I'm pretty sure Ford calls for 75W-140 synthetic for the rear, regardless of limited-slip or not.

80W-90 for front diff.

 

[ahodges]

I'm pretty sure Ford calls for 75W-140 synthetic for the rear, regardless of limited-slip or not.

80W-90 for front diff.

yes that is right. Auto Zone and the repair manuals say 80W-90 all the way around but that isn't right. I don't know if this was related or coincidence, but the first time I changed mine I used conventional 80W-90 and a week later I had an axle seal leak....

 

[gavin]

yes that is right. Auto Zone and the repair manuals say 80W-90 all the way around but that isn't right. I don't know if this was related or coincidence, but the first time I changed mine I used conventional 80W-90 and a week later I had an axle seal leak....

coincidence

I've used 80W-90 in my rear diff.
being in Alaska, it doesn't need the heavy stuff since it doesn't get all that hot. And of course the lighter weight helps a bit with gas mileage in the winter

 

[ahodges]

coincidence

I've used 80W-90 in my rear diff.
being in Alaska, it doesn't need the heavy stuff since it doesn't get all that hot. And of course the lighter weight helps a bit with gas mileage in the winter

lol. ok I've been wondering. That makes sense for you too seeing how it is much cooler there in the summers.

 

[ranger7ltr]

Using Mobil 1 Synthetic 80w-90 in Texas...

For the non LSD differentials I would swear that the FSM specified 80w-90...Well I drained the diff and installed 5 pints of Mobil 1 and in the heat of the Texas summers I didn't have a problem...On the advice of others I poured in about 4 oz. of friction modifier a month or so later and I didn't notice any difference...I believe the friction modifier was overkill...

 

[gavin]

For the non LSD differentials I would swear that the FSM specified 80w-90...Well I drained the diff and installed 5 pints of Mobil 1 and in the heat of the Texas summers I didn't have a problem...On the advice of others I poured in about 4 oz. of friction modifier a month or so later and I didn't notice any difference...I believe the friction modifier was overkill...

hmm... I have my LSD axle back under my truck now, but still have the 4.10 non-LSD axle sitting in my garage. Not sure if I still have the axle tag for it, but I want to say the non-LSD also said 75W-140; I certainly could be wrong, though.

And yeah, if you use full synthetic gear oil, you most likely won't need any friction modifier. I've never put any in, anyway, and never got any chattering.