GL5 with friction modifiers

Status
Not open for further replies.
Joined
Jun 9, 2012
Messages
1,089
Location
Reno, NV
I recently put Peak Limited Slip Synthetic 75-90 GL5 gear oil in my '95 Miata (Thorsen) axle. I understand the Thorsen axle doesn't require the LS oil. My thought was any rear axle is going to have very similar requirements for lubrication (still has a ring and pinion gear for example) so the LS type lube would be fine. Am I missing something?
 
Originally Posted By: brandini
1 - Torsen
2 - LS additives will just do nothing if you don't have a clutch type LSD and they won't hurt anything


If your application doesn't require FM don't put it in because you CAN hurt something. They are needed for limited slip differentials but they are bad for oxidation and seals so you have to use just what is needed and no more. There is a DEXRON spec fluid that already contains FM and another that does not for that very reason. Both are commercially available and the list of suppliers can be found on gmdexron.com. They are both 75W-90 GL-5. Let me know if you can't find one.
 
Last edited:
I have heard people say NOT to use any LS FMs in Torsen diffs (due to there needing to be a certain level of friction between the worm gears and the case in order for there to be a torque biasing function-was the explanation).

But then GM has told people to add 4 ounces of their own LS FM fluid to the LS1 f bodies' T-2 Torsens to help quell the coast down "rocks in a box" sound some were making.

21.gif
 
Who in GM said that? Torsen does not need or want FM.

Are these people talking to dealers to get this advice? We have been using Torsen diffs for years in Europe without problems so unless you have a different issue there is more to know. Tell me are you using this as a final diff or a centre diff?
 
Last edited:
Torsens don't need or want FM. Maybe they are just recommending an inappropriate fluid. Which is why I asked where this recommendation is coming from. I need more information about the application, the specific vehicle and where this recommendation came from.
 
Last edited:
Originally Posted By: redbone3
I recently put Peak Limited Slip Synthetic 75-90 GL5 gear oil in my '95 Miata (Thorsen) axle. I understand the Thorsen axle doesn't require the LS oil. My thought was any rear axle is going to have very similar requirements for lubrication (still has a ring and pinion gear for example) so the LS type lube would be fine. Am I missing something?


The Torsen diffy works on the principle of torque bias and the construction is composed of all gears and does not have clutches, so it does not need an additional LSD fluid.

http://www.youtube.com/watch?v=Z9iPqIQ_8iM

Just because it is called a Limited Slip Differential (LSD), this does NOT mean it needs an LSD additive.

As Whitewolf and others asked, "where is this information coming from?"

I suspect you are getting bad information.
 
Last edited:
I don't know about GM, but Ford calls for XL-3 FM in their diff fluids for Torsen diffs in the late model Mustang Boss 302 and the GT500. Source is both the owner's manual and the shop manual. I presume they did it so that service techs didn't have to think when they service the rear axle.
 
What I have told you about FMs is not a point of debate but well proven information supported by data.
 
Originally Posted By: jaj
I don't know about GM, but Ford calls for XL-3 FM in their diff fluids for Torsen diffs in the late model Mustang Boss 302 and the GT500. Source is both the owner's manual and the shop manual. I presume they did it so that service techs didn't have to think when they service the rear axle.


Here is the only data I can find (so far) on the XL-3 FM:

Quote:
Description: Specially formulated additive to provide smooth operation of clutch-type limited-slip differentials.
 
I found this on the Torsen website:

Torsen for GM vehicles:

Is it true that the Torsen unit in the production Camaro needs the GM modifier added? Top of the Page

GM issued a technical bulletin adding modifier to the rear axle oil. This was done to quiet what we call a "Rusty Screw" noise that we heard in a very small percentage of vehicles. This does not happen in all cases, however to address owner's concerns we asked that the modifier be used in all instances to insure that the driver would not get this noise. When replacing the fluid it is at the owner's discretion whether or not to add the modifier. Elimination of the modifier does not affect durability of the differential.
 
It depends on the advised change interval but it is well proven that FMs reduce the life of a gear oil when compared to a non FM version of the same formulation.
 
Originally Posted By: redbone3
I found this on the Torsen website:

Torsen for GM vehicles:

Is it true that the Torsen unit in the production Camaro needs the GM modifier added? Top of the Page

GM issued a technical bulletin adding modifier to the rear axle oil. This was done to quiet what we call a "Rusty Screw" noise that we heard in a very small percentage of vehicles. This does not happen in all cases, however to address owner's concerns we asked that the modifier be used in all instances to insure that the driver would not get this noise. When replacing the fluid it is at the owner's discretion whether or not to add the modifier. Elimination of the modifier does not affect durability of the differential.


Does the GM tech bulletin mention a part number such as GM #88900330 or some other "modifier?"

The description for this product says:

Quote:
The additive reduces friction between your limited slip or positraction differential friction plates to eliminate the annoying chatter that is common with these types of units. This Chevrolet Performance limited slip lubricant additive not only quiets your rear-end, but it can also aid in your differential's ability to apply and release the clutch smoothly, creating a more pleasant and predictable power delivery.


There are no clutches in the Torsen.
 
Maybe the product has more than one use? For example: Maalox is sold as a digestive product, but it can also be used on stainless steel bolts and nuts to prevent galling.
 
Originally Posted By: redbone3
Maybe the product has more than one use? For example: Maalox is sold as a digestive product, but it can also be used on stainless steel bolts and nuts to prevent galling.


Right. I suspect the FM is used to reduce the "nails-in-a-can" noise found in some Torsen's.

Just trying to figure out how an LSD additive would affect this noise.
 
Originally Posted By: MolaKule
Originally Posted By: redbone3
I found this on the Torsen website:

Torsen for GM vehicles:

Is it true that the Torsen unit in the production Camaro needs the GM modifier added? Top of the Page

GM issued a technical bulletin adding modifier to the rear axle oil. This was done to quiet what we call a "Rusty Screw" noise that we heard in a very small percentage of vehicles. This does not happen in all cases, however to address owner's concerns we asked that the modifier be used in all instances to insure that the driver would not get this noise. When replacing the fluid it is at the owner's discretion whether or not to add the modifier. Elimination of the modifier does not affect durability of the differential.


Does the GM tech bulletin mention a part number such as GM #88900330 or some other "modifier?"

The description for this product says:

Quote:
The additive reduces friction between your limited slip or positraction differential friction plates to eliminate the annoying chatter that is common with these types of units. This Chevrolet Performance limited slip lubricant additive not only quiets your rear-end, but it can also aid in your differential's ability to apply and release the clutch smoothly, creating a more pleasant and predictable power delivery.


There are no clutches in the Torsen.


My guess is that it slightly reduced the case to outer worm gear friction, just enough to eliminate the noises.

I remember this TSB, even though it did NOT affect me since I had already changed out the T-2 for an Eaton carbon clutch pack Posi (about a year after I bought the car), which DOES need some FM to not 'rusty screw', or chatter around slow, parking lot speed turns, or no torque applied, coasting turns.
wink.gif
 
Originally Posted By: dailydriver
Originally Posted By: MolaKule
Originally Posted By: redbone3
I found this on the Torsen website:

Torsen for GM vehicles:

Is it true that the Torsen unit in the production Camaro needs the GM modifier added? Top of the Page

GM issued a technical bulletin adding modifier to the rear axle oil. This was done to quiet what we call a "Rusty Screw" noise that we heard in a very small percentage of vehicles. This does not happen in all cases, however to address owner's concerns we asked that the modifier be used in all instances to insure that the driver would not get this noise. When replacing the fluid it is at the owner's discretion whether or not to add the modifier. Elimination of the modifier does not affect durability of the differential.


Does the GM tech bulletin mention a part number such as GM #88900330 or some other "modifier?"

The description for this product says:

Quote:
The additive reduces friction between your limited slip or positraction differential friction plates to eliminate the annoying chatter that is common with these types of units. This Chevrolet Performance limited slip lubricant additive not only quiets your rear-end, but it can also aid in your differential's ability to apply and release the clutch smoothly, creating a more pleasant and predictable power delivery.


There are no clutches in the Torsen.


My guess is that it slightly reduced the case to outer worm gear friction, just enough to eliminate the noises.

I remember this TSB, even though it did NOT affect me since I had already changed out the T-2 for an Eaton carbon clutch pack Posi (about a year after I bought the car), which DOES need some FM to not 'rusty screw', or chatter around slow, parking lot speed turns, or no torque applied, coasting turns.
wink.gif



You could be right. Maybe I am trying to over analyze this thing, something I have never done in my life, of course.
grin.gif


But if you look at the simulation, torque forces are being transferred purely across the gearing, so the only thing left in my view would be the bearings in the gear carriers. AKA, reactive forces causing wobble in the bearings that could be dampened out by the polymers in FM.
 
Originally Posted By: Whitewolf
It depends on the advised change interval but it is well proven that FMs reduce the life of a gear oil when compared to a non FM version of the same formulation.

Link to data?
 
There is no link. I would have to post an example of what I can show but it is not a point of debate it is a very well known fact throughout the lubricant industry.
 
Status
Not open for further replies.
Back
Top