Hello 6speed members,

Spring is in the air, and it's time to start bringing your cars out of hibernation for the coming year. To celebrate this, we're going to put one of our differentials on sale.

Our torque biasing differential is a significant upgrade to your gearbox and will get more of your power to the ground. For someone who isn't a serious racer, it's the most cost effective no hassle solution to a better differential in your car. Being gear driven, these differentials do not have a service interval on them like a clutch type LSD does. They also don't require a break in period or the added cost of changing your gear oil more frequently like an LSD. They are great for canyon carving, auto-crossing and open track days.

Regular price on them is $1895. For the next 30 days, we're going to offer them at 20% off. That makes your price $1515 plus shipping. They can be purchased either directly through us, or through one of our authorized resellers who would be installing the unit for you. I currently only have a dozen units on the shelf. If we sell out in less than a month, when they are gone they are gone.

Specialist installation is strongly suggested. In addition to the LSD you will need a set of early G50 bolt in axle flanges, replacement side and axle seals, as well adjustment shims. New carrier bearings are not required but suggested as cheap insurance while you are in there. These are all item you should be able to source through the shop that does the install for you.

Please feel free to post up with any questions and I'll do my best to answer them in a timely fashion. PMs. direct emails, and phone calls are all welcome if you prefer.

Kind Regards,

Matt

 

Matt, would you mind clarifying for me the difference between this and clutch type LSD. I track my car and figure the clutch type would be what I would need, but I would like to understand the differences and pros and cons of each. Thanks.

 

Hello Larry,

I would be happy to explain the differences. The torque biasing (TBD)or torque sensing differential is a gear driven differential. They have certain advantages and disadvantages when compared to a clutch type LSD.

For starters, I want to be very specific in how I categorize this differential. Some of the other vendors who sell different brands of TBDs do actually refer to them as an LSD. This is not true. There isn't actually a limit to the slip on a TBD. They don't reach a certain slip percentage and lock the way that an LSD does. This goes both ways. The advantage is that there's no mechanical limit to the difference in speed between the two wheels side to side. On an LSD when the forces between the two wheels (and by default the wheel speed) gets too great it will lock and instead of rolling, that inside wheel that wants to go slower actually slides. This is why a high locking percentage on corner exit can introduce oversteer, for example. That's the low speed lock up and chatter people complain about sometimes when the drive an aggressive LSD on the street. The TBD doesn't suffer from that. You can turn as tight or as wide as you want with it and it will always split the power side to side, constantly changing the split based on traction and wheel speed.

But there's trade offs with the TBD design. In a zero traction situation, the TBD behaves just like an open diff. So, if you cut a corner at the track and hop the inside wheel off the curb, while that wheel is in the air, the one on the ground gets no power. With an LSD, that wheel would still be driving you forward.

The other big tradeoff is on braking. The TBD gives you zero lockup on braking. An LSD does, which is part of why they are so valued on 911 racecars, because they make the rear end just that much more stable and planted. However, we've been seeing something interesting with the AWD turbo cars in particular. An LSD does introduce some corner entry push to the chassis. The AWD cars are already notorious for having corner entry push, and as such, some guys are wary of adding any more after they've done all the suspension work to get rid of it. For them, a TBD is a viable solution. The TBD does not change the chassis dynamics in the same way that an LSD does and will require far less re-tweaking of your suspension setting after installation. We've got a number of guys out there at this point running TBD's in turbo cars who feel it improved their track performance with no added push and no liability on the street when they hop in the car to drive it to work on Monday

However, this brings up a point I want to be very clear about. We do not consider the TBD the best option for racing. Aside from the purely performance perspective, the other part is the design and durability of the parts. While the gears on the TBD are service free and should not require replacement in anything under a decade of service, what we've seen in a track setting where cars, especially high powered turbo cars, are running at the limit for extended periods of time, they just don't hold up. This is somewhere that the serviceability of the LSD and the ability to easily and cost effectively rebuild them is part of what makes them better than a TBD for racing. If you race the car and are trying to place your car on the podium, the LSD is the way to go. Period.

But that is not to say that you cannot or should not take a TBD to the track. For a street car that sees weekend track days and DE use, they are great balance point. Your car will be faster out of the corners with the TBD than it was with the open differential. It would be faster still with an LSD, but you have to ask yourself how serious you are about your "racing" and if that added margin is worth another $1000+ of investment in your gearbox. If you're like me and it's how you blow off steam then it might not be worth buying an LSD. My personal 914, which I do track, does not have an LSD in it. I run a TBD in that car and am quite happy with it. Our shop is currently building a 911 SWB vintage racer, and I wouldn't consider that car properly done if it didn't get an LSD. It's a question of grays that only the individual can decide for themselves and their usage.

Please let me know if I've adequately answered your questions, and if I have raised more that need addressing, fire away. I'm always happy to chat.

 

Excellent explanation, very clear for me.

 

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