Torsen gear oil

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17
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FL USA
I'm looking to install a Eaton/Detroit TrueTrace Torsen differential in the near future. The owners manual states: --- Detroit Truetrac® High quality mineral gear lubes are required for use in Detroit Truetrac differentials. Regardless of the lube type, always use a GL5 rated lube with the least amount of friction modifier. Mineral lubes lacking friction modifiers (limited-slip additives) were historically recommended for all Truetrac applications because friction modifiers can slightly reduce the bias ratio (limited-slip aggressiveness) of Truetrac differentials. However, to address the continually increasing power outputs of modern powertrains, many vehicle manufacturers have switched to synthetic lubricants as a counter measure for increased axle temperatures and prolonged service intervals. In general, consult the vehicle owner's manual for the manufacturer's recommendations for lubrication type, weight and fill volume. This will ensure lube compatibility with the seal materials and bearings used in the axle. Eaton Performance technical support is available for any concerns in lube selection. --- The factory fill recommendation for the OEM rear-end is a synthetic 75W90, but the factory differential was not a Torsen design. I'll be using either the OEM axles, or aftermarket replacement axles. Some are saying "140 is too heavy for a Torsen. No manufacturer will recommend an oil that heavy, it will change the friction levels the diff relies upon to function to its fullest", while others are saying the 140 will reduce noise. Application will be daily driver that sees some autocross and HPDE sessions (20 minute sessions of limited passing). I've found the following gear oils without friction modifiers, should I consider any of these or look elsewhere?
 

JimMueller

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17
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FL USA
Stumbled across this from another Torsen manufacturer. It sounds like the 90W offers slightly more friction than the 140W. https://torsen.com/lubricant-part-2/ "For our own R&D work, we use Chevron Supreme LS 80W90 as a “house” oil. That leads me to another point. While a differential like the Torsen Type-2 is happy in whatever good quality oil that you may choose, oil weight (viscosity) comes into play with regards to performance. As I stated earlier, Torsen works by generating internal friction. So, logically, if different oil blends have different frictional properties, that mean they have different influences on the differential’s behavior. Essentially, the heavier, thicker, or more viscous that the oil is, the better it lubricates (generally). It leaves a heavier film adhered to the surfaces being lubricated. This reduces friction. But, that means that a differential operating in 75W-140 oil will have fractionally less locking effect than the same unit operating in 75W-90. This difference is not night and day – the changes are subtle. But if you’re fine-tuning a race car, it does offer one more knob that you can turn. By the same token, lubricant formulation and additives used have a similar bearing on the matter." Here's an updated chart.
 
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2,005
Location
Jacksonville, FL
I'm running plain old Super Tech 80w90 in my TrueTrac axle and have no complaints 15,000 miles in. Tons of bite. If I was going to use a Synthetic gear lubricant in it I was planning on using Redline NS which is on your list, pick the viscosity that suits the manufacturer recommendation and use the Redline if you want a Synthetic.
 

JimMueller

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17
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FL USA
If I'm understanding correctly, it seems to be a tradeoff between the additional load protection of the 140 vs. the slightly better friction allowed by the 90. Since I plan to use an OEM ring & pinion, and the OEM lubrication is recommended to use a 75W90, I guess I should stick with the xxW90. Looking at the viscosity numbers for the xxW90 blends in the chart, which is better for my application?
 
At one time, I owned an '01 Camaro, which came stock with a Torsen differential. Except for the first 500 miles, I used Red Line Heavy Shockproof Gear OIl for the entire 15 years and 136,000 miles I owned the vehicle. I sold the car with the original rear axle in the the car. Periodically, I had lube samples analyzed and wear metals were always normal. Never had any noise from that axle and the Torsen diff always worked great existing turns.
 

JimMueller

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17
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FL USA
I haven't found any 75W110 that explicitly states it doesn't contain friction modifiers, and I'd also prefer to see the tech specs on it for comparison. Everything I've found on Redline's site regarding their three Shockproof varieties indicates it's extremely slippery, which means less friction for the differential, and also not to be used with coolers.
 
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15,004
Location
Santa Barbara, CA
My Mustang came from the factory with a Torsen T-2. Factory fill and recommended replacement is 75W140. I changed the factory fill out at 5K with Amsoil 75W140.
 

MolaKule

Staff member
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21,695
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Iowegia - USA
Originally Posted By: JimMueller
I haven't found any 75W110 that explicitly states it doesn't contain friction modifiers, and I'd also prefer to see the tech specs on it for comparison. Everything I've found on Redline's site regarding their three Shockproof varieties indicates it's extremely slippery, which means less friction for the differential, and also not to be used with coolers.
And Redline never defines "Slippery." Slip, Friction, Friction Coefficient, Traction Coefficien, etc., are scientifically definable terms in Tribobology, but "Slippery" is not.
 
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3,756
Location
Massachusetts
Originally Posted By: Hib_Halverson
At one time, I owned an '01 Camaro, which came stock with a Torsen differential. Except for the first 500 miles, I used Red Line Heavy Shockproof Gear OIl for the entire 15 years and 136,000 miles I owned the vehicle. I sold the car with the original rear axle in the the car. Periodically, I had lube samples analyzed and wear metals were always normal. Never had any noise from that axle and the Torsen diff always worked great existing turns.
I read on the corvette forum that you drained heavy shockproof from your 4 speed blazer and forgot and drove it for a good distance on the highway. Curious how that turned out. Did it live for a long time?
 

JimMueller

Thread starter
Messages
17
Location
FL USA
I guess I'll just go with the 75W-90NS, I know another fella that uses that fluid with the same car model, diff & rear end for open track events.
 
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1,855
Location
Australia
I ran Motul Gear 300 (non LS) in an Ashcroft ATB (Ascroft Transmissions torque biasing centre, their version of a Torsen T2 or Quaife ATB) in a centre diff as it's an MTF/transaxle fluid. It worked very well.
 
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