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Differential Oil

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DampLemonade

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Compiled some info from threads that were a couple years old at this point. Wanted to see what people are thinking these days. I have the 2500 tradesman 4x4, gas 6.4L, with a 3.73 "anti-spin" diff which I understand is the same thing as limited slip. Very quickly approaching 20k miles, mostly towing on the highway

Leaning towards Amsoil Severe Gear 75w85. Amsoil says it already contains LS modifiers so I shouldn't need additional additives?
Sounds like exactly 4 quarts will get it just below fill level?
Gasket is reusable.

For the front diff, also leaning towards the Amsoil 75w85. Should take 2 quarts and also has a reusable gasket? I use the 4x4 on occasion but more wanted to replace the factory oil with Amsoil since it sounds like the factory oil isnt too good.

Anything important I'm missing? Overall sounds like a pretty easy afternoon job. I'll get 7 quarts oil total just to be safe.
 
its very simple job. Amsoil makes great gear oil. 75w90 will work. if you tow often, 75w140 might be a better choice for the rear.

Fill about 3/8" below the fill line to prevent cavitation in the oil.

I think the front axle will take close to 3 pts.

I dont add LS modifiers when using amsoil. (or any of the major oil brands). never had an issue.
 
Any big differences between the 75w85 and 75w90? Theyre the same price for me online.

I heard some guys in other threads warning against the 75w140 unless it was in a dually or relatively warm area. I did run the -140 in my older GMC 2500 but it was really sluggish during the winter. We'll touch -10F to -20F here in the colder parts of the year.
 
Amsoil Severe Gear is the way to go. 100% get the squeeze pouches.

75w-85 in the front, change it and forget about it for 100K miles.

75w-90 in the rear is all you should need with a Hemi, and for most Cummins owners too. Run it for 40-50K miles and replace it if you tow frequently.

75w-85 will yield marginally better economy that you probably can’t measure but 75w-90 will protect the diff better.
 
AH64ID said:
Amsoil Severe Gear is the way to go. 100% get the squeeze pouches.

75w-85 in the front, change it and forget about it for 100K miles.

75w-90 in the rear is all you should need with a Hemi, and for most Cummins owners too. Run it for 40-50K miles and replace it if you tow frequently.

75w-85 will yield marginally better economy that you probably can’t measure but 75w-90 will protect the diff better.
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Safe to re-use the gaskets or need to buy new?
 
I can't understand in this day and age why any manufacture would even make diff fluid that doesn't already have the modifier in it. You would think the Mopar bottle would have it in there by now.
 
flan said:
Do any?

I have seen some housings with a drain plug in the bottom.
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The only ones that I know of that have a drain plug in the bottom are Toyota because they have third member style differentials, which do not have covers.

The Ford rear end I put in my jeep didn’t even have a fill plug on the cover. It’s on the housing
 
Rockcrawlindude said:
The only ones that I know of that have a drain plug in the bottom are Toyota because they have third member style differentials, which do not have covers.

The Ford rear end I put in my jeep didn’t even have a fill plug on the cover. It’s on the housing
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Not on the cover is ok, but not having it on either the housing or the cover is kinda annoying.

Blame it on the bean counters as the cost of boring and tapping a drain hole costs more than just letting it spill out when popping the cover off.
 
downsc123 said:
If you rarely use 4-wheel drive, is t here really any reason to change the front diff oil?
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Doesn't matter. The shafts and spiders are spinning 100% of the time you are going down the road.

Moreso, the front diff doesn't generate enough heat to drive out moisture, so anything that accumulates via the vent hose or otherwise becomes chocolate milkshake in there. Change it even if you don't use it, but especially because you don't use it. I've seen plenty of chocolate milkshake on "never off road" and "never 4x4 trucks." Another 2.5 quarts of fluid isn't going to break the bank.
 
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dieselscout80 said:
Not on the cover is ok, but not having it on either the housing or the cover is kinda annoying.

Blame it on the bean counters as the cost of boring and tapping a drain hole costs more than just letting it spill out when popping the cover off.
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FWIW, the older GM duramaxes with AAM housings have a drain plug on the bottom of the housing. Some of the ford/sterling axles have a cover bolt that breaks through to the inside and functions like a drain plug, so you have to RTV it on reassembly.
 
downsc123 said:
If you rarely use 4-wheel drive, is t here really any reason to change the front diff oil?
Click to expand...
You should not treat it any different than the rear, obviously you don't have the same load on the front as the rear if you tow(weight of motor?), but you can get moisture in the front diff. Its also not a bad idea just to inspect the internals once in awhile. I did my rear at 13K, I have 23k now and I had planned to change the front sooner but have been procrastinating -
 
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