Differential Additives

[Jesusisgod]

It looks like on amsoil, they say to still add 5 oz of the mopar limited slip additive. For a 2024 1500 bighorn with 3.21 diff. It also says the capacity is 4.2 pints. If I'm mathing correctly. That means total it'll be 4.5 pints, 4.2 being 75w-90, and .3 pints of the mopar slip additive?

Also if I'm reading on here correctly. The front differential only needs 75w-90. It does not get the additional mopar additive?

So if what I'm told is correct. the front differential isn't a limited slip. It is an open diff that uses the brakes to slow the spin if one side is spinning and the other isn't?

My next question would be what changed between the years from 2020 to 2024. That the oil capacity went from 5.68 to 4.2?

This will be the first time ive done a differential fluid change. So my plan is to follow my friends advice. As well as a few YouTube channels.

Drain fluid on rear. Put in 5 oz of mopar additive. Fill with 75w-90 till it just stsrts to drip from fill hole. Then close up.

On the front. Drain then fill only with 75w-90 till it just starts to drip from the fill hole. Close up and done.

Any advice or corrections to what I'm wrong about is greatly appreciated! Thank you in advance.

 

[Richard320]

I have no idea about capacity. But you are correct -- the front is an open differential and doesn't need additive. The technique is correct, additive then fill 'til it runs out.

 

[1BADRAMLIMITED]

SOUNDS SPOT ON.

 

[Bt10]

I assume the additive is only for the anti spin differential? Both the open and locker wouldn’t need the additive for clutch action?

 

[Jesusisgod]

I assume the additive is only for the anti spin differential? Both the open and locker wouldn’t need the additive for clutch action?

I guess that's correct I'm learning all this new. The owners manual doesn't say to use it on the front. Just says on the rear 3.21 and rear 3.55. It's not up to date from what I understand. Amsoil has recommendations on the different gears as well. For instance with or without lsd.

 

[HSKR R/T]

It looks like on amsoil, they say to still add 5 oz of the mopar limited slip additive. For a 2024 1500 bighorn with 3.21 diff. It also says the capacity is 4.2 pints. If I'm mathing correctly. That means total it'll be 4.5 pints, 4.2 being 75w-90, and .3 pints of the mopar slip additive?

Also if I'm reading on here correctly. The front differential only needs 75w-90. It does not get the additional mopar additive?

So if what I'm told is correct. the front differential isn't a limited slip. It is an open diff that uses the brakes to slow the spin if one side is spinning and the other isn't?

My next question would be what changed between the years from 2020 to 2024. That the oil capacity went from 5.68 to 4.2?

This will be the first time ive done a differential fluid change. So my plan is to follow my friends advice. As well as a few YouTube channels.

Drain fluid on rear. Put in 5 oz of mopar additive. Fill with 75w-90 till it just stsrts to drip from fill hole. Then close up.

On the front. Drain then fill only with 75w-90 till it just starts to drip from the fill hole. Close up and done.

Any advice or corrections to what I'm wrong about is greatly appreciated! Thank you in advance.

Are you sure you have the limited slip differential? It would have been an option on the window sticker.

 

[Jesusisgod]

Are you sure you have the limited slip differential? It would have been an option on the window sticker.

I believe it said antispin rear differential. To my knowledge they are the same thing. I don't have the window sticker beside me right now. But on the ram app it says my options. As far as I know it's correct.

 

[HSKR R/T]

I believe it said antispin rear differential. To my knowledge they are the same thing. I don't have the window sticker beside me right now. But on the ram app it says my options. As far as I know it's correct. View attachment 185892

Yep, that's it. Just wanted to make sure, as that was an option, and not standard. And you don't need the additive if you don't have it.

 

[Jesusisgod]

Yep, that's it. Just wanted to make sure, as that was an option, and not standard. And you don't need the additive if you don't have it.

Do you mind me asking why? Like I said this is all new to me.

 

[HSKR R/T]

Do you mind me asking why? Like I said this is all new to me.

The additive is called friction modifier. It allows the clutches to have more "grip" allowing them to function properly and not slip as easily. But also prevents chatter.

 

[Tinscrew]

It looks like on amsoil, they say to still add 5 oz of the mopar limited slip additive. For a 2024 1500 bighorn with 3.21 diff. It also says the capacity is 4.2 pints. If I'm mathing correctly. That means total it'll be 4.5 pints, 4.2 being 75w-90, and .3 pints of the mopar slip additive?

Also if I'm reading on here correctly. The front differential only needs 75w-90. It does not get the additional mopar additive?

So if what I'm told is correct. the front differential isn't a limited slip. It is an open diff that uses the brakes to slow the spin if one side is spinning and the other isn't?

My next question would be what changed between the years from 2020 to 2024. That the oil capacity went from 5.68 to 4.2?

This will be the first time ive done a differential fluid change. So my plan is to follow my friends advice. As well as a few YouTube channels.

Drain fluid on rear. Put in 5 oz of mopar additive. Fill with 75w-90 till it just stsrts to drip from fill hole. Then close up.

On the front. Drain then fill only with 75w-90 till it just starts to drip from the fill hole. Close up and done.

Any advice or corrections to what I'm wrong about is greatly appreciated! Thank you in advance.

Must be international Diff Day. I just swapped out my rear diff today after visiting my local Amsoil dealer. I have a 3.92, but the sheet he printed out for me matches your understanding for the rear on a 3.21 with LSD.



I didn’t do the front, haven’t even put it in 4WD yet. Here is what sheet reads for the front tho.

 

[Jesusisgod]

Lol i haven't done it yet I ordered the stuff yesterday. The reason I wanna go ahead and do the front with the rear. My understanding is even though it's not in 4x4 the front diff still turns on these 1500s. Watched some videos about it yesterday. He put a gopro under the truck and the front drive shaft definitely turns in 2 wheel.

 

[Tinscrew]

Lol i haven't done it yet I ordered the stuff yesterday. The reason I wanna go ahead and do the front with the rear. My understanding is even though it's not in 4x4 the front diff still turns on these 1500s. Watched some videos about it yesterday. He put a gopro under the truck and the front drive shaft definitely turns in 2 wheel

 

[Jesusisgod]

?

 

[Tinscrew]

?

Woops - yeah, so that’s new info. If the front is as easy as the back, then I might do that next weekend. Thanks!

For the back, the torque specs I used are 18ft lbs for the 8MM and 44 for the 14MM - tho, you can get by with ‘feel’ since you will be loosening them. I see that question asked a lot with no definitive answer.

 

[Jesusisgod]

Woops - yeah, so that’s new info. If the front is as easy as the back, then I might do that next weekend. Thanks!

For the back, the torque specs I used are 18ft lbs for the 8MM and 44 for the 14MM - tho, you can get by with ‘feel’ since you will be loosening them. I see that question asked a lot with no definitive answer.

Looks like the channel on YouTube was the Getty adventures. The title is just why your front differential always spins in 2wd. I wish he woulda mentioned something about the fluid. I figured might as well just change both. I believe the front is only 1.1 pints.

Thank you I woulda been wondering I didn't even think to look it up tq specs.

Here is a link I never see anyone talk about. It's a bit expensive to use for personal vehicles. It's incredibly useful. Its what my friend uses at the shop he works for. Detailed step by step with tq specs and what not.

Select Vehicle | ALLDATA

www.alldata.com

 

[HSKR R/T]

Must be international Diff Day. I just swapped out my rear diff today after visiting my local Amsoil dealer. I have a 3.92, but the sheet he printed out for me matches your understanding for the rear on a 3.21 with LSD.

View attachment 185922

I didn’t do the front, haven’t even put it in 4WD yet. Here is what sheet reads for the front tho.

View attachment 185923

You should at least put it into 4-auto every now and then to cycle the shift solenoid and linkage. Otherwise it could not work when you do want to use it.

And you already saw the gears in the differential still turn even when not in 4wd

 

[Tinscrew]

Agreed and good point HSKR R/T. Will do & I do need to do that.

Your post reminded me to create my signature.

Its new btw, w/ 2,000 miles atm. The diff fluid change.... new truck love and a reason to wrench on this weekend.

 

[Brutal_HO]

The additive is called friction modifier. It allows the clutches to have more "grip" allowing them to function properly and not slip as easily. But also prevents chatter.

Actually, friction modifier provides more slip, that's what prevents the clutches from chattering. It reduces the coefficient of friction in the fluid trapped between the clutch material. Shudder is caused by rapid transitions from stick to slip. The friction modifier makes the fluid slicker to prevent the shudder caused by this transition. The clutches still grip but achieve that grip in a smoother more linear manner.

 

[BlueHemi1500]

All,
I'm in the learning phase as well.
So I am sure I have just a regular rear axle in the 4x4 truck with no special gears.
So what happens if one were to add the Mopar Friction Modifier fluid when doing the fluid change along with the required rear-end gear oil to a standard ratio, standard rear-end differential?
Just curious if this would be detrimental?
I can't be the only one that has this question rattling around in my head.

BlueHemi1500