Rear gear fluid change

[ARedmon]

I'm going to change the rear diff fluid soon. My truck is a 2014 3500 diesel and is almost exclusively used for towing a 5th Wheel camper. It has 22,000 miles on it. My question is: What brand/weight fluid is recommended? Since it's used for towing, I was thinking a 75w140 synthetic? How many quarts does it hold? It has a limited slip rear diff so do I need a friction modifier? The truck is a 4x4 but since it is rarely in 4wd, I figured the front diff could go to 50,000 miles or more before a change. Does that sound reasonable? Thanks in advance for any suggestions/info.

 

[gsbrockman]

Any 75W90 GL5 Full Synthetic fluid will be fine. The owner’s manual doesn’t specify 75W140 for heavy towing.....not sure it would hurt anything but maybe the fuel economy. Purchase 4 quarts and you’ll have a little left over; no friction modifier is required. I think starting in the 2015 MY RAM went to 75W85, and is only available through the dealer. Lots have used the 75W90 without any issues though.

Some, including myself, have found that condensation forms in the front differential sooner than one imagines. I’d at least pull the plug and see if you can determine if it’s milky looking or not.

Additionally.....is your truck AISIN equipped and does it have the finned aluminum rear differential cover? If so.....you’ll need an external star socket in size E10 for the removal of the fasteners.

 

[ARedmon]

Yes, it is Aisin equipped with the aluminum rear diff cover. Thanks for the heads up. Does the truck have a re-usable diff cover gasket?

 

[Ozymandias]

Yes, it is Aisin equipped with the aluminum rear diff cover. Thanks for the heads up. Does the truck have a re-usable diff cover gasket?

yes

 

[Dasmoeturhead]

gsbrockman has summed it up.

 

[gsbrockman]

Yes, it is Aisin equipped with the aluminum rear diff cover. Thanks for the heads up. Does the truck have a re-usable diff cover gasket?

It does, as already mentioned. Include are some old file pics of mine.
You can see the reusable gasket still hanging on the rear axle.
#ad

 

[gsbrockman]

External star socket I bought at O’Reilly Auto Parts...#ad

 

[ARedmon]

Thanks for the info and the pics, guys! I will go today and pick up some star sockets. If I decide to do the front diff also, is there anything different I should know? I assume I can use the same fluid? I know the front diff is an open type so the friction modifier is not required in it either. I guess the front cover also has a re-usable gasket? Just out of curiosity, do you know why a friction modifier is not required in the limited slip of my truck? I haven't done much mechanic work in a long time (getting too old!). Back in my younger days, though, I always added a friction modifier to a limited slip rear-end.

 

[Cummins12V98]

You already went over the recommended interval for the rear diff when towing. Did you experience any grabbing when taking off and turning while towing?

I highly advise AMZ/OIL SevereGear 75-110 if you are towing a lot.

60k on these gears towing 33-35k combined. Minuscule amount on magnet.

I would do the front at the same time and go with the SG 75-90.

 

[GrantP]

Thanks for the info and the pics, guys! I will go today and pick up some star sockets. If I decide to do the front diff also, is there anything different I should know? I assume I can use the same fluid? I know the front diff is an open type so the friction modifier is not required in it either. I guess the front cover also has a re-usable gasket? Just out of curiosity, do you know why a friction modifier is not required in the limited slip of my truck? I haven't done much mechanic work in a long time (getting too old!). Back in my younger days, though, I always added a friction modifier to a limited slip rear-end.

Same fluid front and rear. Yes the front cover also has a reusable gasket. A friction modifier is not required because there are no clutches in the LSD.

 

[ARedmon]

Thanks again, guys! I think I'm ready to do the job now. Appreciate all the info and the great pics!

 

[Newsa]

The dealer service dept i spoke with said they will only use mopar synthetic with the friction modifier additive already in it on a heavy duty truck. The friction modifier makes it slipperier. Not required, but helps lube in my opinion.

I'd go with amsoil, redline or other high quality synthetic since you are extending the lube service interval. 75-110 or even 75- 140

 

[Cummins12V98]

I talked to AMZ/OIL about the rear diff on my new to me 01 2500 auto Sport. They said I did NOT need to use the slipLoc in the rear diff as the SevereGear already had the modifier.

 

[kthaxton]

I think most synthetics these days do not require the additive for limited slips.....whether it is an actual additive, or just the inherent slippery-ness of synthetics, I do not know.

 

[Newsa]

I think most synthetics these days do not require the additive for limited slips.....whether it is an actual additive, or just the inherent slippery-ness of synthetics, I do not know.

It usually says on the bottle label if it has the friction modifier in it

 

[smittyd174]

I bought mine at the dealer got it for same price as most compatable brands . Takes 7 qts to do both. Easy job but awkward to fill. Dont forget the transfer case which takes 2 qts of fluid.

 

[Cummins12V98]

I bought mine at the dealer got it for same price as most compatable brands . Takes 7 qts to do both. Easy job but awkward to fill. Dont forget the transfer case which takes 2 qts of fluid.

OE fluid is not as good as other synthetic GL's. Be careful and don't run it over 15k if towing.

 

[JackFate]

I bought mine at the dealer got it for same price as most compatable brands . Takes 7 qts to do both. Easy job but awkward to fill. Dont forget the transfer case which takes 2 qts of fluid.

May I ask how much ? I was quoted $17 a qt. Said list was $25

 

[Cummins12V98]

For far less $$$ AMZ/OIl SevereGear 75-90 or 75-110 if towing.

 

[EDankievitch]

I've been very happy with Royal Purple 75-90 wt gear lube. Just did my rear end after having to replace a wheel seal that leaked all over my e break. I change the fluid every year/ 25k miles give or take. This year I'm happy to say there was No metallic fuz on the magnet. Things have finally broken in. Only took 98k miles.