Diff maintenance - Which fluid?

HS-LD · Sep 21, 2017

So FCA calls for 75w85 GL5 synthetic fluid for front and rear differential service. And NO additional limited slip friction modifier needed.

Red Line makes a 75w90 GL5 in both a limited slip variety and non-limited slip variety.

I want the non-limited slip variety for front and rear, right?

I have the 4.10's with the rear limited slip.

Just checking in for opinions...

(Update: So after digging a little, it seems that the reason that FCA calls for no limited slip additive is that the limited slip function is actually computer controlled. I guess they are using the brakes on the spinning wheel to fool the other wheel into driving... that's a guess.)

G. Mcpherson · Sep 21, 2017

I would sat Redline would be a great product to use. I use it for my Motor oil.

SETEX 6.4 · Sep 21, 2017

I'm running Amsoil Severe Gear 75w110 front and rear.

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SETEX 6.4 · Sep 21, 2017

No it's because our anti spin is gear driven not clutches like the 1500's

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BlkZrx · Sep 22, 2017

Put RL 75-140 in mine, tow an 8k lb. TT..

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loveracing1988 · Sep 23, 2017

It seems they changed the oil since my 2014, but the axles are the same. You can either run the 75w90 or 75w85 it isn't going to make much difference. If it were me I wouldn't run anything thicker than that though, you'd want that for added gearset protection and thr thicker oil should protect better but will flow a lot harder on the bearings which is the wear item on the axle. Just as long as it is a synthetic oil you'll be fine, you can use the one with friction modifyer, it won't hurt anything but it isn't needed. Like said a few posts above it is a helical style lsd vs clutch style, the clutch style is the one that needs the modifyer.

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SETEX 6.4 · Sep 23, 2017

loveracing1988 said:
It seems they changed the oil since my 2014, but the axles are the same. You can either run the 75w90 or 75w85 it isn't going to make much difference. If it were me I wouldn't run anything thicker than that though, you'd want that for added gearset protection and thr thicker oil should protect better but will flow a lot harder on the bearings which is the wear item on the axle. Just as long as it is a synthetic oil you'll be fine, you can use the one with friction modifyer, it won't hurt anything but it isn't needed. Like said a few posts above it is a helical style lsd vs clutch style, the clutch style is the one that needs the modifyer.

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Exactly the reason I'm running Amsoil 75W-110 little thicker but not to thick!
Just how I like other things!

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loveracing1988 · Sep 23, 2017

SETEX 6.4 said:
Exactly the reason I'm running Amsoil 75W-110 little thicker but not to thick!
Just how I like other things!

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Yes, but why? The oil in them from the factory is what it is designed to use so why change it? I've seen these axles run for days at a load that is way beyond anything you'll ever tow and the fatigue breaks them not the oil being too thin. About the only thing you are doing is making the wear on the pinion bearings go up.

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SETEX 6.4 · Sep 23, 2017

loveracing1988 said:
Yes, but why? The oil in them from the factory is what it is designed to use so why change it? I've seen these axles run for days at a load that is way beyond anything you'll ever tow and the fatigue breaks them not the oil being too thin. About the only thing you are doing is making the wear on the pinion bearings go up.

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Just because I wanted to I guess!
I feel it's better protection. No I don't have scientific data to back that up but I do feel that the trucks are designed to meet the needs of the most uses. NOT ALL USES.
In my opinion it's kinda like the suspension.
Yeah Ram made them good but Thuren makes them bad ass. Ram makes a good oil but I feel like a company that designs and makes nothing but makes better oil. Like Amsoil. There is not that huge of a difference between 75W-85 or 90 and 75W-110.
Just a little thicker at times and more protection imo. Now there is a huge difference between 75W-85 or 90 and 75W-140. That is to thick also in my opinion.
That is why. May not be your opinion of why but it's mine.

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loveracing1988 · Sep 23, 2017

SETEX 6.4 said:
Just because I wanted to I guess!
I feel it's better protection. No I don't have scientific data to back that up but I do feel that the trucks are designed to meet the needs of the most uses. NOT ALL USES.
In my opinion it's kinda like the suspension.
Yeah Ram made them good but Thuren makes them bad ass. Ram makes a good oil but I feel like a company that designs and makes nothing but makes better oil. Like Amsoil. There is not that huge of a difference between 75W-85 or 90 and 75W-110.
Just a little thicker at times and more protection imo. Now there is a huge difference between 75W-85 or 90 and 75W-140. That is to thick also in my opinion.
That is why. May not be your opinion of why but it's mine.

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Kind of like apples and oranges but ok. Suspension is designed to haul a load and ride ok. Change the springs and you'll gain a better ride, height, articulation etc.
The oil though is designed to go above and beyond what the truck is capable of, the same oil a 2500 takes a dually 3500 takes that can tow 30k. What do I know though, I only test the axles on a daily basis...

HvyDuty · Sep 23, 2017

I did my front and rear at 20k miles and used Oreillys brand 75w-90 synthetic (it was on sale, same price as non synthetic). I plan to change it every 20k miles as I tow frequently.

If I was never going to change it again (most don't) I'd put in the high dollar stuff.

FWIW, the original fluid looked fine, not black or emulsified etc.

Diff maintenance - Which fluid?

HS-LD

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