Switching gear oil weight.

[CamoUnicorn]

Bought a used truck a couple years ago and finally decided to pull the service records from Carfax. Found out relatively recently that it had it's diff. oil changed, and in the front diff. they used Mobil 80W140. No one can really tell me why it was used or the benefits/cons. Question is whether it's safe for the next service to switch to the recommended 75W90. It has 270,000KM and it's a 2008 Ram 3500 6.7.

What are your thoughts on this?

 

[Marcozi]

Check with the truck's manufacturer to see what fluids it recommends.

 

[racer12306]

I think 80w140 is usually a conventional gear oil.

It should be an AAM 11.25". It's not a Chrysler differential.

Definitely no issues in switching back to the recommended grade.

 

[JavierH19]

I thought that's what the 3/4 tons typically used. But if you don't tow or it gets extremely cold where you are you can go to a lower grade without worry.

 

[CamoUnicorn]

Check with the truck's manufacturer to see what fluids it recommends.

Manual says 75W90 - just wanted to make sure nothing terrible would happen

 

[CamoUnicorn]

I thought that's what the 3/4 tons typically used. But if you don't tow or it gets extremely cold where you are you can go to a lower grade without worry.

In the winter we can regularly see temperatures well below zero

 

[ShearStable]

Manual says 75W90 - just wanted to make sure nothing terrible would happen

Amsoil Severe Gear 75w90. I used it in multiple vehicles, even over 140,000km in one diff. Ran great!

 

[thastinger]

The front diff oil I change at 30K intervals in all of our 4WD vehicles always looks as good as new, while the rear diffs you can tell they have had use.
I would leave it and switch to 75-90 on the next service.

 

[tnt_motorsports]

I run 75w90 in my front and rear diff in my 2012 Ram 2500. I service it regularily because I tow a decent amount, and I stick with what the manual states (75w90). My last fill was Mystik. I've used Mobil 1 & Valvoline in the past.

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Just my $0.02

 

[twX]

In the winter we can regularly see temperatures well below zero

With gear oils, there is a big difference in cold viscosity between each grade. 75W is tested at -40 C, and 80W is tested at -26 C. There can be a large variance in cold flow performance between different oils within each grade as well. I'd expect most 80W140 gear oils to be on the thicker side of what's allowable for an 80W. I'd switch to a 75W90 before winter if temperatures could be below -20 C.

 

[2013ecof150]

The only Mobil 80w140 I’ve seen is Delvac and it’s synthetic. Mobil also makes an 85w140 that’s conventional.

 

[barkingspider]

The front diff oil I change at 30K intervals in all of our 4WD vehicles always looks as good as new, while the rear diffs you can tell they have had use.
I would leave it and switch to 75-90 on the next service.

This!