Redline MTL 75w80- Ferrari Mondial QV gearbox improvement

MolaKule

Staff member
Joined
Jun 5, 2002
Messages
23,027
Location
Iowegia - USA
Are these lubricants likely to cause issues in manual transmissions that don't ask for these lubricants?

For example, the two MTF's I go to (Fuchs Sintofluid 75w80 and Millers Oils TRX 7w5w80) are both rated GL-5. I use them in older gearboxes such as the R380 in the Defender.
Probably not but I would not consider them to be Lifetime MTF's.

Also, I can't see any advantage of these fluids over say Pennzoil Synchromesh or the Valvoline Synchromesh MTF'S when the spec is for a GL-4 at ~ 10cSt.

See post #20.
 
Last edited:
Joined
Sep 19, 2022
Messages
24
Do not run GL-5s in a MTX that is not approved for them, specifically in a synchronized manual gearbox. In a NOT-synchronized gearbox it should be fine, but compatibility with the synchros is a potential issue. "Bigger number does not always mean better."
 

MolaKule

Staff member
Joined
Jun 5, 2002
Messages
23,027
Location
Iowegia - USA
Do not run GL-5s in a MTX that is not approved for them, specifically in a synchronized manual gearbox. In a NOT-synchronized gearbox it should be fine, but compatibility with the synchros is a potential issue. "Bigger number does not always mean better."
See post #18 regarding the chemistry of GL-4/GL-5 MTF's.
 
Joined
Sep 19, 2022
Messages
24
Oh I saw it.

You run whatever you want. Unless the manufacturer of the gearbox approves GL-5 lubricants (some of them get rather specific as to what's approved and what's not) you're playing with fire thinking that "higher number is better" and if a particular lube has both ratings on it that does not mean its safe for the synchros.

The issue isn't usually corrosion "per-se." It's the EP additives; the way they work is by forming a film on the gear face through chemical bonding, which shears first under extreme load when the gear ends up in what's called a boundary condition (that is, the pressure is high enough that there is no film of oil between the two pieces.) That's good; the metal is protected and is the point.

Except -- if that bonding is stronger than the synchronizer material guess what happens.....

BTW its a royal biatch to rip a MTX apart and replace the synchronizers.....

I have two cars in my driveway right now that are FWD and thus have combined differential/MTX sumps. Both specify GL-4 and both have run it since they were new, with myself being the only one who has ever changed said fluid since they came from the factory. One has 300,000 miles on it, the other 225,000. Both have zero evidence of synchronizer or differential trouble.

The Redline MTL mentioned up-thread is specifically a GL-4 fluid; I run it in my Mazda as it meets manufacturer specifications. That's the one with 225k miles on it (the other is a MTX Jetta TDI.)

BTW one oddity -- the MTL claims to be GM Auto-Trak II compatible. I dunno about that; I won't run it in my Suburban's transfer care, only the OE GM "Blue" fluid since mine has "auto" mode and there are plenty of reports of those blowing up if you run something else, even though it allegedly is "compatible." The setups without "auto" mode (push-button lock, but no "auto" mode) are supposedly ok with non-GM OE fluid; the issue is claimed to be with the clutch system in the ones that have "auto" capability.
 

Attachments

  • redline.jpg
    redline.jpg
    216.4 KB · Views: 7
Last edited:

MolaKule

Staff member
Joined
Jun 5, 2002
Messages
23,027
Location
Iowegia - USA
...if a particular lube has both ratings on it that does not mean its safe for the synchros.

The issue isn't usually corrosion "per-se." It's the EP additives; the way they work is by forming a film on the gear face through chemical bonding, which shears first under extreme load when the gear ends up in what's called a boundary condition (that is, the pressure is high enough that there is no film of oil between the two pieces.) That's good; the metal is protected and is the point.
We're discussing a properly formulated and application specific MTF that has a GL-4/GL-5 rating which would be safe.

You seem to be ignoring the chemistry's called metal inhibitors and corrosion inhibitors, all which act as agents to combat any copper-alloy synchronizer assembly problems.
 
Joined
Sep 19, 2022
Messages
24
If the manufacturer specifically states it is compatible with a synchronized manual gearbox (and you believe they'll stand behind that if your synchros are destroyed) then have at it. I have no reason to believe yours isn't perfectly ok -- I'm sure it is -- but carrying both ratings on the label by itself IMHO is not enough because in a hypoid-gear differential said dual rating has no chemistry or film-strength concerns.
 

MolaKule

Staff member
Joined
Jun 5, 2002
Messages
23,027
Location
Iowegia - USA
If the manufacturer specifically states it is compatible with a synchronized manual gearbox (and you believe they'll stand behind that if your synchros are destroyed) then have at it. I have no reason to believe yours isn't perfectly ok -- I'm sure it is -- but carrying both ratings on the label by itself IMHO is not enough because in a hypoid-gear differential said dual rating has no chemistry or film-strength concerns.
Your last sentence is confusing and I am not sure what it says.

Again, We're discussing here a properly formulated and application specific MTF that has a GL-4/GL-5 rating which would be safe for copper-alloy synchronizer assemblies. An MTF with a GL4-/GL-5 rating ALSO has an additional component called a "Friction Modifier" for the synchronizer assembly to insure proper meshing and spin-up forces.

(Copper-alloy synchronizers here imply a Bronze or Brass metal machined alloy).

A hypoid gear differential lube, once again, has to have a GL-5 rating with the proper EP additive because of it high loading. Loading here means there are high contact forces in the gear teeth and high reaction forces against the bearings and shims.

The EP additive prevents galling of the tooth contacts.

Here is what I posted on Oct. 13, 2017:

"It is NOT what is MISSING but rather the DIFFERENCES between gear fluids of different ratings: Dedicated or Application Specific MTF’s for Manual Transmission or Transaxle use an additive package containing Anti-Wear (AW) additives, rust and corrosion inhibitors, emulsifiers, and specialized Friction Modifiers, and are generally protection rated at the SAE GL-4 level. Now GL-4 does not necessarily refer to MTF’s, as there are some gear lubes in the Market place that are GL-4 rated, but are not MTF’s. GL-4 is an SAE wear protection rating. There are a few MT fluids GL-5 rated for specific vehicles that have common MT and Differential sumps. One such manufacture, Subaru, has transmissions which shares a common sump and require a MTF which is GL-5 rated; but the Subaru-type fluids also contain special friction modification chemistry for the synchro assembly. Manual Transmission fluids use a different Friction Modifier for synchro engagement, a modifier that is NOT the same Friction Modifier chemistry as used in differential lubes, engine oils, or hydraulic fluids. Here, Friction Modifier or Friction Modification does NOT refer to friction reduction. Here, Friction Modifier refers to a chemical compound that gives rise to a situation such that the coefficient of friction (COF) varies Dynamically with respect to the relative speed of parts that mesh and de-mesh during engagement and disengagement of rotating parts. In summary: 1. GL-5 and MT1 rated gear lubes have a higher viscosity than MTF's of the same SAE Gear Oil viscosity range, 2. GL-5 and MT1 rated gear lubes have a different additive package than do MTF's; MTF's contain Anti-Wear additives, GL-5 and MT1 rated gear lubes contain Extreme Pressure (EP) chemistry. 3. GL-5 and MT1 rated gear lubes have a different additive package than do MTF's; MTF's contain specialized Friction Modification chemistry; GL-5 and MT1 rated gear lubes containing LS additives have special Friction Modification chemistry that is different than what is found in MTF's."


See also:
'

and

 
Last edited:

jayg

Thread starter
Joined
Oct 4, 2012
Messages
1,342
Location
Rabbit Creek, Alaska
I wonder how a good quality synthetic 75w90 gear oil would work in this transmission?
The Royal Purple Gearmax that I recently mentioned in another thread claims to be GL4/GL5.
I would think it would be better cold than 80w90 and better hot than 75w80 but what do I know....I'll probably never get to drive a Ferrari to find out.

Very few report alternative 75w90 help at all, most report it shifts the same. No other 75w90 combo I have used ever changed anything. That RP isn't going to do what needs to be done in this box. Again, the technical article I posted details the actual issue and no brand of thicker fluid is going to make it work without physical. modification to the box. The ticket is the thin fluid. It's been flawless since switching to the MTL with no chatter from the LSD. I wish I had done it 10 years ago in my 308gt4 that had the same issues.

Somebody else mentioned it wouldn't be a good idea to run it hard in AZ heat with that combo but one of the most respected Fcar techs (In TX and services in high volume) does just that along with folks the track their cars too for many years with no difference in wear. Really there has been no downside.
 
Top