axle oil and limited slip additives

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Yarek

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Hi guys. A week ago I got myself a 2001 Ram 2500 SLT, with a V10 engine, automatic transmission, 4x4, and a limited slip differential (judging from the DSA code on the sticker in the glove box compartment).

The truck runs pretty good, has 129k miles on it, it's been lifted a good 8", but it does look like the maintenance has been quite deferred on it. I plan to take it on longer trips, and so I want to make sure all the fluids are new, properly filled etc. Some things are easier than others, mostly because some things are more clearly explained in the documentation than others. The task at hand is replacing the oil in both front and rear axles. I figured out by now, that the stock axles were Dana 70 in the back, and 60 in the front. So far so good. DSA code indicates that it's limited slip, but when I read the documentation regarding the anti-slip additive, they only mention adding it to the rear axle, not a word about needing it in the front. Am I missing something? should I add it to both axles, or just the rear? What additive do you guys recommend?

Also, regarding the oil itself. The manual lists SAE 80W90 for the front, and SAE 90W in the rear, however, looking on-line I see people using SAE 75W140. I know, people tend to have very strong opinions on oils and I'm not trying to start a big discussion... Needless to say, if there is a single oil that will work well in both axles, that would be great. I'll only need one container. Storage space is at premium. My motorcycle uses 80W90, although a very tiny amount. Still, I wouldn't complain if I could get away with stocking just one type.

For context: I plan to get a good size RV trailer, and I will be doing some moderate off-roading, so 4x4 will be used, and the truck will see some towing loads. I live in California and don't envision driving this thing a whole lot in winter, but rather in hot summer weather, and quite a bit of climbing through the Sierra mountains, so things will stay pretty warm.

So yeah, any recommendations you may have, please share.

For context: here are some options I found on Amazon:
1) 75W-140, with limited slip additive in it already, and that's over $10/qt
2) 85W-140 without the additive, only $4/qt!
3) 80W-90, without the additive, exactly what I run in my motorcycle, $5.39/qt

Original Mopar limited slip additive is under $10/4oz, so from that standpoint, I don't see a reason to pay $6 extra per quart of oil, if the 80W-90 works, or even if the 85W-140 works.
Reading further on it, I can see that running a thinner oil in the front, could save me $$$ on gas, so in that case I'd be leaning towards the 80W-90 in the front, just like the manual specifies, and maybe 85W-140 in the back?

In the meantime I need to get myself some RTV and a 1/2" drive torque wrench. My 1/4 and 3/8 will be inadequate for the work ahead of me...
 
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crash68

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Let me throw another wrench in the works, Mobile 1 75W-90 synthetic gear oil, it has the additive.
Truthfully your probably fine using the 80W-90 that you use in the motorcycle and adding the friction modifier.
 
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Yarek

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so you're saying the limited slip additive is needed in both, front and rear axle?
 

crash68

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so you're saying the limited slip additive is needed in both, front and rear axle?
No, a friction modifier is only needed for clutch type limited slip differentials. Your front axle is most likely an open differential.
 
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Yarek

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Thx!

Just ordered the stuff: 80W-90 for the front, and 85W-140 for the rear, and the Mopar additive, just for the rear.
 
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