Tag Archives: lube

Tech Info, Maintenance

Lubricant & You: Part 2

Part Two: Previously, we talked about some of the basics of choosing the correct oil for your Torsen differential. Now, can get into a little bit more depth. You may recall that that the Torsen® will operate in whatever oil makes your ring gear happy. However, that is not to say that all oils are equivalent in the eyes of your differential – they’re not. There are a lot of quality aftermarket lubricants out there with a lot of fans that will swear by using them. And that’s great. But be wary of off brand products that you’ve never heard of, or don’t meet some sort of SAE standard. So, again, that’s great, so what would we recommend?

Unfortunately, we aren’t in a position to effectively compare multiple brands of lubricant. It would certainly be interesting to study. Imagine conducting a secret, blind taste test of all the popular brands (Brand-RL, Brand-RP, Brand-Am, Brand-M1, etc) in our lab, and comparing the results. The results would probably be fascinating.  But a test like that has a lot of variables and takes a lot of time.  In the end, it would still only offer a slice of what factors are important.

Such a comparison would only tell us what offers the “best” differential performance. It would say nothing about secondary effects on the rest of the axle or transmission system. So, it isn’t a real practical endeavor. Most of the testing that we conduct is with oil provided by our OEM customer, for use with their product. I should point out that OE manufacturers conduct extensive testing, using their preferred lube. They validate the entire system with that oil. This should not be overlooked, as the testing is typically quite rigorous.  It is, however, a point that a lot of people miss.

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.

Generally, synthetic lubricants have lower friction properties than conventional, non-synthetic oils do. Synthetic lube may still be preferable if the duty is severe or high temperatures are a concern. Synthetics typically offer superior performance in those areas due to a more durable molecular structure. The overall friction properties of the lubricant are also influenced by additives and modifiers blended in. Clutch type differentials typically need these modifiers. They help to even out the transition from static to dynamic coefficients of friction between the clutch plates. This, in turn, smooths out their operation and reduces chatter. However, it also means that they may slightly lower the overall differential locking performance as well.

Lubricants sold as “limited slip oils” have these additives premixed in. Be aware of this when making a selection. For OEM applications, the validation testing that I referred to above includes extensive vehicle handling and chassis dynamic tests. Consequently, the OEM oil (and differential performance) is matched to the intended handling behavior for that car. So, where does that  leave us? Quite simply, here: use a good quality product, one that meets the needs of your ring & pinion gearing. Beyond that, think about what your specific needs are and choose accordingly.

Tech Info, Maintenance

Lubricant & You: Part 1

Part One: Perhaps the most common question we hear, here at Torsen® Intergalactic Central, is “what oil do you recommend?” It seems simple enough, right? Well, not so fast there, pal – it’s not a black and white matter. You may have heard that oil is your engine’s life blood; for all the geared systems within an automobile that is also true. Typically, the differential shares its lubricant with other components. In a rear axle, that includes the ring & pinion set as well as the axle bearings.  For a front wheel drive transaxle, however, that also includes the entire transmission system.  This entails the gears, the bearings, the syncros, everything.  The catch is that a limited slip differential – like Torsen – works by creating friction. On purpose. So, you have to balance proper lubrication with allowing the differential to do its job. That means a trade-off.

In reality, a limited slip differential is the only (oil-lubricated) component within a vehicle that intentionally produces friction. Friction within the differential is what gives it resistance to wheel slip.  And, as previously noted, the ability to transfer torque in an advantageous way. So, choosing a type of oil that has minimal reduction of friction is the obvious answer, right? Yet, the differential is spinning on bearings within the axle.  That whole system uses the same oil, including the final drive gearing.  It all needs proper lubrication to survive. Gear life directly depends on proper lubrication.  Lubrication also has a direct impact on other factors, like fuel economy. This is why lube choice is tricky – and why vehicle manufacturers spend a lot time testing, both for performance and for durability.

In truth, a Torsen differential typically isn’t that fussy about which lubricant you choose – within reason. A Type-2 or T-2R model will operate in really any common lubricant, ranging from ATF to heavy weight gear oil. On the other hand, if you happen to be using a Type-1 differential, you need to a little more choosy.  The crossed-axis gear mesh of Invex™ gearing requires the use of oil with high-pressure additives. This means they need gear oil with a GL-5 rating. But even that isn’t too difficult.  Hypoid ring & pinion gears have the same need, so almost all normal axle lubricants are up to the challenge. But be sure to look for the rating on the bottle anyway.

Because the ring & pinion final drive gearing are constantly running, they are a lot fussier regarding proper lubrication. So, your best bet is to seek out the recommendation of the ring & pinion manufacturer. If your car came with a Torsen from the factory, then you can find that information in your owner’s manual. Or, if you’ve installed a different gear set or changed ratios, go back to the supplier or manufacturer of the gearing you used. Most are very specific about what fluids should be used during break-in and normal operation of their gears. But either way, if the lube is suitable for your final drive gearing, the Torsen will be happy as well.