Do I need friction modifier

[Bub]

My 2002 Chevy HD is coming up on a rear diff fluid change( 4.10 ratio with with limited slip). My question is do I need friction modifier(I don't know what kind of limited slip it is) some need em some don't.
Thanks
Bub

 

[sprintman]

Use Redline of the correct viscosity, and they also have an additive that can be used to 'tune' an LSD if required.

 

[Pablo]

Use Amsoil Series 2000 synthetic gear oil and you shouldn't need an LSD additive. If you do want to it's compatible with the additives out there.

 

[OneQuartLow]

Stick with RedLine 75W90 or 80W140 and you shouldn't need additional friction modifier. Only the "NS" versions would need it for clutch-based limited slip packs. Even then their FM bottles are ~$5.

Excellent oil. I've used many quarts and it definitely drops temps. Haven't had noisy gears to quiet so I can't speak to that.

Sadly, I'm back to dino since I've had to change fluid every 2 months on average. (water contamination)

David

 

[BOBISTHEOILGUY]

Most of the gear oils are now coming with the friction modifiers built into the oil. On occasion, you may find it necessary to add additional FM's. The easy way to tell is to install the new fluids, drive up to temp, then do so figure 8's in a parking lot. If the rear end starts to making pop'n sounds, then a FM should be added to the existing fluid otherwise there should be no problem.

If you use a gear oil such as the Redline or Schaeffers(which NO ONE ever mentions

) you'll find more times than not will you ever need the fm additive as they both use moly and will reduce any friction developed and actually give you better performance/and most cases better fuel mileage due to this. I cannot speak for amsoil as I don't know if theirs contains any moly or just uses heavier does of zddp like standard gear oils use.

 

[jason07-1zzfe]

Actually Red Line does NOT use moly in most of their gear oils. Which ones, I don't know.
In an email I asked if their gear oils contain molybdenum and he said they do not use it in most of their gear oils because it isn't really necessary or offer a benefit.

 

[MolaKule]

Yes, but I will bet they (Redline) uses some type of AW additive. Their esters can act as Friction Modifiers, but if you need Anti-Wear/EP additives, you need some type of organometallic additve (sulfur, phosphor, nitrogen, moly, borate, barium, timbucktoo, whathaveyou) to function as such.

 

[Bub]

Thanks guys, appreciate the input.
Bub

 

[Mike_dup1]

AMSOIL gear oils are formulated with friction modifiers for limited slip differential applications. There is no need to add limited slip or additional additives.

Although generally not necessary, original equipment manufacturers' limited slip additives may be used in conjunction with AMSOIL Series 2000 Synthetic Gear Lube.

[ December 11, 2002, 06:29 PM: Message edited by: Mike ]

 

[MolaKule]

Mike,

There may be some exceptions and I am specifically referencing aftermarket LS internals.

The Auburn LS in my Burb will chatter with any of Amsoil's GL's, even the S2000 74W140.

Edit in response to Bob's inquiry below:

"The only oil that I have used to-date that has not chattered is the Redline 75W140. Have not used Schaeffer's as yet to determine if it shows the same non-chatter conditions as Redline."

I have also determined that GM's LS additive doesn't do well in this differential as it shears to a thin creamy substance in < 6 months.

[ December 12, 2002, 03:33 PM: Message edited by: MolaKule ]

 

[BOBISTHEOILGUY]

quote:

---

Originally posted by MolaKule:
Mike,

There may be some exceptions and I am specifically referencing aftermarket LS internals.

The Auburn LS in my Burb will chatter with any of Amsoil's GL's, even the S2000 74W140.

The only oil that has not chattered is the Redline 75W140.

---

Have you tried the schaeffers gear oils in that unit, and if so did it chatter? or should the post read, the only oil I have tried so far that didn't chatter is redline?

[ December 11, 2002, 07:41 PM: Message edited by: BOBISTHEOILGUY ]

 

[Bub]

As to Molekule's statement about GM limited slip additive. I have found that it does not last very long in early LS1 F-car diffs (some early models use an auburn style diff) either. My Z's diff chattered when I bought it, so I added the FM. About 10,000 miles later it needed another dose of the stuff to get it to shut up again. The truck that I started this thread for is also getting a case of the chatters after only 9 months. If this has anything to do with LS additive I don't know, but the chattering diff is the reason I'm changing the lube.
Bub

[ December 19, 2002, 01:04 AM: Message edited by: Bub ]

 

[JWRENCH]

I am in the process of changing mine also. I just found out if you have the G-80 production code locking diff as most new GM trucks have, It does not need any additive in the lube. I'm putting Redline 75w-90ns in mine.

 

[OneQuartLow]

Ah, the G80 uses an Eaton gov-lok. It uses clutches, but not like usual LSD's. Once you get above ~200rpm differential between wheels it engages right now. Quite different from the progressive slipping of traditional packs that need a narrow range of lube friction.

Edit: BTW, this is not a pedaltothemetal locker/lsd. Learn to engage it and back off so as not to break fuses. Cases I've heard of were with oversize tires but it's something to be conscious of.

David

[ December 20, 2002, 03:01 AM: Message edited by: OneQuartLow ]