What Differential oil to use for Torsen?

[SCALECRAFT]

Hi All

I am going to install a Cortex watts link to my 14 Shelby. This involves putting on a new diff cover and will need new oil.

What diff oil is used. I track my car.
Thanks
Steve

 

[Patrick@Steeda]

Use Motorcraft 75w 140. We found that gears last longer with Motorcraft than any other oil in our race car.

 

[SCALECRAFT]

Thank You

 

[carguy19]

I used amsoil 75w 140 race oil. Works great.

Dead silent even with my 3.73 gears.

 

[Ghoust]

Do you have the Performance Package? If so I was told to go with a lighter weight oil.

 

[Norton]

According to p42 of the Owner's Manual Supplement, 75W-85 is required in all 2013/2014 MY GT500s.

 

[carguy19]

According to p42 of the Owner's Manual Supplement, 75W-85 is required in all 2013/2014 MY GT500s.

Ive run the amsoil full synthetic since it came out in every 8.8 and 9 inch ford rear I ever owned, and I never had a broken part or whine or peep out of my rear ends. This is on the more then 15 mustangs Ive owned.... with gears from 3.55 to 4.56.

I don't give a F what ford recommends. People who build chassis and rear ends every day swear by the stuff. It hasnt let me down so I run a heavier duty then what stock recommends. I have never had one issue with a rear and on every mustang I've owned I've changed ratios.

So I guess I am partial. LOL

I recommend it to everyone with a mustang. Traction lock, torsen, Detroit no matter

 

[Ablaze]

I've also ran heavier weight Amsoil in all my 8.8s and they've all been silent, beaten on almost immediately. I plan to do the same with this one.

 

[Norton]

Ive run the amsoil full synthetic since it came out in every 8.8 and 9 inch ford rear I ever owned, and I never had a broken part or whine or peep out of my rear ends. This is on the more then 15 mustangs Ive owned.... with gears from 3.55 to 4.56.

I don't give a F what ford recommends. People who build chassis and rear ends every day swear by the stuff. It hasnt let me down so I run a heavier duty then what stock recommends. I have never had one issue with a rear and on every mustang I've owned I've changed ratios.

So I guess I am partial. LOL

I recommend it to everyone with a mustang. Traction lock, torsen, Detroit no matter

I've also ran heavier weight Amsoil in all my 8.8s and they've all been silent, beaten on almost immediately. I plan to do the same with this one.

FWIW, I agree with both of you regarding Amsoil being a better option. (I run Amsoil Severe Gear 75W-90 in mine.)

I simply provided the manufacturer's recommendation (which is generally a good place to start) in response to the suggestion that lighter weight oil is required for SVTPP cars. As I stated, Ford recommends their own 75W-85 for both SVTPP and non-SVTPP cars. IMO, Amsoil Severe Gear 75W-90 is a better option. I'm not comfortable running the previously recommended 75W-140 with the SVTTP cooling system, as it seems like it would be more viscous than what the system was designed to handle.

 

[carguy19]

FWIW, I agree with both of you regarding Amsoil being a better option. (I run Amsoil Severe Gear 75W-90 in mine.)

I simply provided the manufacturer's recommendation (which is generally a good place to start) in response to the suggestion that lighter weight oil is required for SVTPP cars. As I stated, Ford recommends their own 75W-85 for both SVTPP and non-SVTPP cars. IMO, Amsoil Severe Gear 75W-90 is a better option. I'm not comfortable running the previously recommended 75W-140 with the SVTTP cooling system, as it seems like it would be more viscous than what the system was designed to handle.

My car is not a track pack. I would run the thinner oil if I had a track pack.

I agree with your points for sure.

My car is a street/strip car so the track pack would have never been a thought for me. I ordered my car with everything but the track pack and glass roof.

 

[TORQJNKY]

What Amsoil weight do you guys recommend for a Detroit Tru-Trac, 3.73 gears and Track Pack? I don't road course my car but it has the track pack. I've heard not to run synthetic with a Tru-Trac but I've also seen guys do it with no issues. Thanks.

 

[UnleashedBeast]

In the case of a Tru-Trac differential, Eaton states it relies on friction to work properly, and to use a conventional gear oil (read cheap dino gear oil). This seems to be the popular consensus for this unit, stating true synthetic lubricants will modify the operational bias of the differential. In other words, it may not function as intended with a true synthetic gear oil that has a natural lower frictional coefficient of the base oil and additive content. I prefer Amsoil Severe Gear, however....I'd test cheap gear oil first, then possibly upgrade and test again. Your results may vary.

Here is a respected member from a lubrication forum on the topic.

I was not aware ARB recommends mineral... mostly because there is nothing technical in the new or old design that really makes a difference one way or another as far as I can see.

The Trutrac limited slip differential (LSD) is another matter. Syns can certainly effect the bias ratio of the unit, which relies on gear interference... i.e. friction. The friction characteristics of the oil is part of what delivers the designed bias ratio. I was told by engineers at Tractech (this was before the Eaton buyout) that syns weren't necessarily harmful to the unit, but they reduced the bias ratio and changed the LSD's operational characteristics. In some cases, a chirping/squealing from the Truetrac has been noted with certain syn oils. I have a few specifics on a couple of other LSD but won't note them here & now.

From what I know, few of the companies that offer aftermarket traction aids and recommend only mineral oils have even investigated the use of syns extensively. That cuts into the profit margin after all and complicates things. Easier to recommend a lube that meets the standards of the oil the unit was calibrated to. Even so, there are many Truetrac owners running syns. I don't currently with mine but I have in the past with no adverse effects readily apparent (did not test bias).

At different times over the past 25 years, I've talked with reps from the various companies that offer traction aids and have found a lack of interest in investigating the modern lubes. Thing is, the design of most of the traction aids on the markets predate the common use of synthetic oils (many date back to the 1930s, '40s or '50s). These old units were calibrated to mineral oils. It might require redesigning the unit to make it fully compatible with synthetic oils. With minerals still common, and frankly better than ever, what incentive is there for the money and energy to be spent to do that. Much easier to say "mineral oil only" and leave it at that because they know it works.

That leaves individual owners to experiment on their own. If they dare! In most cases, I think the worst result is a decrease in effectiveness. There may be some exceptions to that. I don't have a lot of specifics but there appears to be some brands of oil that work well in certain units and others that don't. The old rumor was that Mobil 1 syn gear oil caused the Truetrac to squeal but Amsoil didn't. I don't know about the Mobil 1 but I used Amsoil in my Truetrac with no adverse effects. I can't speak to the loss of bias because I didn't do any testing. I also don't know if the Mobil 1 thing was even true but it illustrates the lack of research and verified information on the subject.

By all means, if you want your traction aid to work and wear as designed, use the recommended oil. That doesn't mean something else, a syn for example, might not work just as well or well enough... you're just on your own as to the results.

Unless you have measured the bias ratio with mineral vs the Amsoil, you really don't know what you've lost. And that's a pretty complex test to make. Seat of the pants, I didn't notice anything in mine either but I have been assured by people who have tested that it's there to some degree. I had a very good contact in the engineering department at Tractech, the company that designed the original Truetrac (Tractech was sold to Eaton) and we had a long conversation about this. They got a LOT of complaints when people ran syns in Truetracs. The thing I couldn't get him to tell me were the brands... he was afraid I'd publish names and it would get back to him somehow. At the time, late '90s-early '00s, it was "common knowledge" that Amsoil didn't cause any particular problems (e.g. the squeal/chirping) but all of the syns cause at least a slight loss of bias ratio. A good deal of this may be moot today since everyone has changed their oil formulation. I don't doubt there is still a loss of bias, but I have no clue how common the other complaints still are.

Thread LINK

 

[TORQJNKY]

In the case of a Tru-Trac differential, Eaton states it relies on friction to work properly, and to use a conventional gear oil (read cheap dino gear oil). This seems to be the popular consensus for this unit, stating true synthetic lubricants will modify the operational bias of the differential. In other words, it may not function as intended with a true synthetic gear oil that has a natural lower frictional coefficient of the base oil and additive content. I prefer Amsoil Severe Gear, however....I'd test cheap gear oil first, then possibly upgrade and test again. Your results may vary.

Excellent explanation. Thanks UB! Can you recommend a conventional gear oil? I'm still inclined to put Severe Gear 75W-140 Amsoil in, but I may try to conventional first.

 

[UnleashedBeast]

Excellent explanation. Thanks UB! Can you recommend a conventional gear oil? I'm still inclined to put Severe Gear 75W-140 Amsoil in, but I may try to conventional first.

Just about anything you buy cheap at the auto parts stores that has Mobil 1, Valvoline, or Pennzoil on it in the correct grade.