[Cekkent]

Anyone running full-synthetic 75w140 in their differential? I'm not really concerned about fuel economy going down, but would like to improve durability.

The only spec for the rear end seems to be 75w90 and that it be full synthetic.

 

[pullinhard]

i run the amsoil 75w140 in the rear, and the 75x90 in the front. the rear see most abuse. i have had good luck with it. last truck 420,000kms on the stock rear end.
its full syn.
its funny that the diesels call for 75w90, but the gas half tons call for the 140?????????i don't get that, but i run what i feel is better. i also run a maghytec cover.it gets expensive to swap over to that oil, but worth every penny

 

[steelhead01]

if you're towing/hauling heavy often, over 10k lb loads, 75w110 or 75w140
especially critical in high temps.

if just an empty daily driver, 75w90 is spec'd and the best for top mpg.

only full synthetic, PAO or ester based, per AAM spec's, to withstand the shear loads produced by high diesel torque loads. not many gas engines can load a rear end like a high torque at low rpm like a Cummins diesel

 

[tajinate]

I had a tranny shop try to tell me it was ok to use Royal Purple 75w-140 in the NV5600, I wasn't buying that one at all! I use RP 75w-90 in the front and back, but as Steelhead01 said, it i mostly a daily driver and rarely if ever tows anything over 10K lbs.

 

[CD in NM]

I've been running the Amsoil 75W-140 in my diffs. I tow a lot, tow heavy, so it seemed the better choice for my use. I am due for a diff oil change, thought I'd try running the 75W110 just to see if my fuel mileage changes. I know several people who have been using the 75W110 and tow heavy, they have had no problems using it. If you tow, the 74W110 and the 75W140 are probably the better route to take.



CD

 

[D-Roc]

Go with what the manual suggests....

 

[mjf6175]

The manual has been updated by a tech bulletin to dealers from Dodge which recommends what the others above have said...if you tow heavy or often, you can use synthetic 75-140 or 75-110. I carry heavy loads in the bed (at times I have had 3-4k) and the diffs, both front and back, have the 75-140 now.

 

[Cekkent]

It looks like on the viscosity specs for 75w-140, it's about 3 times as thick as 15w-40 engine oil, at 104°F. As I don't think that would be good in the cold, I'm going to stick with the 75w-90, and probably go with a larger diff cover. I don't really tow that much.

Thanks for your input!

 

[SN 5.9]

i use dealer items 75/90 syn.

 

[[email protected]]

I have never believed that you make a pick-up to tow and haul heavy and then put in oil that is only good for use as a grocery getter. I use 75/ 85 or 75/90 GL5 oil. I change it often, at 12,000K and will again this fall should be at about 52,000K and I buy good quality, not special priced.

 

[steelhead01]

using Mobil 1 as a common representative diff. gear lube in HD apps., please note that the cold pour point and 40d C viscosity are exactly the same comparing 75w90 and 75w140

will find that other brands of PAO or ester based hypoid GL5 lubes are very similar comparing their cold temp op. specs. between their w90 and w140 lubes.

the significant difference is sheer resistance, load handling and viscosity at high temps.

Dodge does now recommend syn. 75w110 or 75w140 in heavy tow apps. for the AAM 11.5 rear diff.


Mobil 1 Synthetic Gear Lubricant LS 75W-90

Mobil 1 Synthetic Gear Lubricant LS 75W-140

It looks like on the viscosity specs for 75w-140, it's about 3 times as thick as 15w-40 engine oil, at 104°F. As I don't think that would be good in the cold, I'm going to stick with the 75w-90, and probably go with a larger diff cover. I don't really tow that much.

Thanks for your input!

 

[Cekkent]

using Mobil 1 as a common representative diff. gear lube in HD apps., please note that the cold pour point and 40d C viscosity are exactly the same comparing 75w90 and 75w140

will find that other brands of PAO or ester based hypoid GL5 lubes are very similar comparing their cold temp op. specs. between their w90 and w140 lubes.

the significant difference is sheer resistance, load handling and viscosity at high temps.

Dodge does now recommend syn. 75w110 or 75w140 in heavy tow apps. for the AAM 11.5 rear diff.


Mobil 1 Synthetic Gear Lubricant LS 75W-90

Mobil 1 Synthetic Gear Lubricant LS 75W-140

I get two different ones.

From the 75-140 page: cSt @ 40ºC 179
From the 75-90 page: cSt @ 40ºC 106

Pour points are about the same. I don't think i'll be seeing temperatures low enough to worry about pour points.

 

[AH64ID]

The manual has been updated by a tech bulletin to dealers from Dodge which recommends what the others above have said...if you tow heavy or often, you can use synthetic 75-140 or 75-110. I carry heavy loads in the bed (at times I have had 3-4k) and the diffs, both front and back, have the 75-140 now.

Do you have a link to that? The only one I have seen says 75w-140 on anything but the AAM.


I have called and talked to AAM about the axle. They said that 75w-90 is all that is needed unless you are towing at or above GCWR thru Death Valley in the summer. Otherwise they found better results from 75w-90.

Now the 75w-110 Amsoil is a new fluid, and if you tow heavey and tow alot I would reccommend that, but honeslty I don't think you need 75w-140.

 

[NavyDood]

Do you have a link to that? The only one I have seen says 75w-140 on anything but the AAM.


I have called and talked to AAM about the axle. They said that 75w-90 is all that is needed unless you are towing at or above GCWR thru Death Valley in the summer. Otherwise they found better results from 75w-90.

Now the 75w-110 Amsoil is a new fluid, and if you tow heavey and tow alot I would reccommend that, but honeslty I don't think you need 75w-140.

Ditto that. Read the tech bulletin again.

 

[Cekkent]

I guess I never thought to call the actual manufacturer of the axle. 75w-90 it is then! It's cheaper too. :thumbsup::thumbsup: