Which oil for rear LSD?

[RB Will]

Hi All. I've tried looking on the model specific forums but answers seem all over the place.

I'm looking to do a rear diff oil change on my 2004 Ram SRT-10, I believe the rear diff is a Dana 60. The manual says to use the Mopar gear and axle lubricant (oil) and add a bottle of the limited slip additive / friction modifier, shown in the link below

https://www.ebay.co.uk/itm/304416939900?campid=533...

I see these days you can buy synthetic gear oil for use in LSDs, for example

https://www.ebay.co.uk/itm/185621469679?_trkparms=...

Would I be ok to use just the Castrol, as it seems to represent a saving of around £100 for the oil change, and is much easier to get hold of. Or would This also need the friction modifier?

[eth2190]

I'd try it with the Castrol first, and if it seems to be excessively binding/ chirping the tyres on tight car park turns etc. add in some friction modifier.

[stevieturbo]

RB Will said:

Hi All. I've tried looking on the model specific forums but answers seem all over the place.

I'm looking to do a rear diff oil change on my 2004 Ram SRT-10, I believe the rear diff is a Dana 60. The manual says to use the Mopar gear and axle lubricant (oil) and add a bottle of the limited slip additive / friction modifier, shown in the link below

https://www.ebay.co.uk/itm/304416939900?campid=533...

I see these days you can buy synthetic gear oil for use in LSDs, for example

https://www.ebay.co.uk/itm/185621469679?_trkparms=...

Would I be ok to use just the Castrol, as it seems to represent a saving of around £100 for the oil change, and is much easier to get hold of. Or would This also need the friction modifier?

If it's a factory diff, then use factory spec oil.


Otherwise you need to know exactly what type of diff it is, as to determine if it has any special oil needs.

[RB Will]

stevieturbo said:

If it's a factory diff, then use factory spec oil.


Otherwise you need to know exactly what type of diff it is, as to determine if it has any special oil needs.

Well this is part of my problem really. Nervous as to how wrong you can get it?

The manual states to use 90w Mopar gear oil and 1.25 bottles of the friction modifier. Apparently this is one of a few elements the manual is wrong on, it was revised up from the Ram 2500 5.7hemi manual and some things which should have been amended were not, another one is the engine oil volume for example.

People say the manual is wrong and that you should use the stuff I linked above so the 75-140w and 2 bottles of the friction modifier, others say the 90w and one bottle, some others have said as long as it is LSD gear oil it has the friction modifier in it so that is fine, various Dodge dealers have no or varying ideas.

I was wondering if as well as easier and cheaper that the Castrol being ready made might have the modifier at the right level anyway, but seems this is a bit more interesting and involved than I thought.

[Turn7]

Will, try speaking to these guys :

https://www.rrtransmissions.com/

They are very well regarded in Caterfield circles, and market there own specific oil for the Caterham Titian plate diff........

They also know LSD's better than most.

[stevieturbo]

RB Will said:

Well this is part of my problem really. Nervous as to how wrong you can get it?

The manual states to use 90w Mopar gear oil and 1.25 bottles of the friction modifier. Apparently this is one of a few elements the manual is wrong on, it was revised up from the Ram 2500 5.7hemi manual and some things which should have been amended were not, another one is the engine oil volume for example.

People say the manual is wrong and that you should use the stuff I linked above so the 75-140w and 2 bottles of the friction modifier, others say the 90w and one bottle, some others have said as long as it is LSD gear oil it has the friction modifier in it so that is fine, various Dodge dealers have no or varying ideas.

I was wondering if as well as easier and cheaper that the Castrol being ready made might have the modifier at the right level anyway, but seems this is a bit more interesting and involved than I thought.

The fact they claim it needs a friction modifier might suggest it is a plate type diff.

There are plenty of oils out there that are already suitable for this style without adding modifiers. But then you'd wonder why they just didn't use those instead of a two piece solution.

[RB Will]

Pretty sure it is a plated lsd, you can buy replacement clutch packs for it.

Were these ready made oils a thing 25 years back when the manual was written, diff designed?

Maybe it was done as the vast majority of Chrysler Jeep stuff had open diffs and it was easier just to have an additive for the rarer lsd models that came to dealers?

[stevieturbo]

RB Will said:

Pretty sure it is a plated lsd, you can buy replacement clutch packs for it.

Were these ready made oils a thing 25 years back when the manual was written, diff designed?

Maybe it was done as the vast majority of Chrysler Jeep stuff had open diffs and it was easier just to have an additive for the rarer lsd models that came to dealers?

Of course they were, LSD's have been around for many decades. Plated diffs are less common in more modern times though.

The likes of Castrol B373 has been around for as long as I've been driving, and no doubt many years before that. Although synthetics are maybe more common now.