Hey there everyone,
So before I get started here, most everyone knows me from past posts. My name is Erik Johnson and I work for a company that specializes in Porsche Transaxles. We service a wide range of people and applications, including quite a few people here.
There has been quite a bit of talk on some of the other board recently about Limited Slip Differentials, and I thought that some of the information might actually benefit people here, even if you do not have a Porsche transaxle in your car. The information that I am about to write is based on 35 years of company experience, as well as a couple of opinions of my own, so as with most things you find on the net, take it with a grain of salt, as I am sure that there will be some who will not agree with my opinions, and some that will.
So first things first. What does a Limited Slip Differential actually do inside your car? Well it allows both rear wheels to work together to put the HP and Torque of your engine to the ground.
Some of the older crowd will probably still call it Posi-traction, or something similar, but that basic idea is that both rear wheels spin.
In an open differential, only one wheel spins. This can at times be very unsettling to the car, especially if you are trying to put a great deal of power to the road.
In a spool the rear end is locked all the time. This can cause some issues of its own when trying to navigate through a series of tight turns, or worse yet trying to park your car in a parking lot. With both of the rear wheel continuously locked together the inside wheel travels at the same speed as the outside wheel in a turn. One tire therefore, has to skid to keep up with the other in a tight turn. However, when going in a straight line a spool works wonderfully, as the tires will be spinning at exactly the same rate of speed all the time.
Many racers even today like using a spool, even though it is quite tough on the tires, because of the ability to control the rear end strictly with the inputs of the accelerator and brake. If you apply enough power to break the rear end loose, then you can control the direction of the rear end with inputs of both the accelerator and brake, (mostly the accelerator) This was especially fun in the older dirt track cars.
What the Limited Slip Differential brought to the table so to speak, was a blending of both the open differential, and the spool. It offered the ability for both rear wheels, or front too I suppose for front wheel drive cars, to be tied together to put the power down to the road, however, also allowed them to act separately from each other in tighter turns. (Breakaway torque)
Most Limited Slip Differential on the market today are either 4 plate or 8 plate differentials, which means that there are 2 plates per side or 4 plates per side that act like clutches to determine the amount of grip applied to each wheel. These clutches are actuated by the differential ramps which are cut to various degrees, which directly effects the amount of torque applied to the friction plates, and plane plates. These plates are what actually keeps both wheels spinning together.
So LSD 101 right? Here is where it gets interesting. I have seen most people make the mistake of understanding the LSD most when it actually comes to the ramp angles. I will try to explain this the best I can here so that maybe it will make a bit more sense.
A 40/60 differential does not mean 40% lockup on the Acceleration side of the differential and a 60% lock up on the deceleration. This is a common mistake that people make. 40/60 is actually the degree angle that the ramps are cut at. It should be understood that this means 40 degrees / 80 degrees, not %.
So what does that mean? Well here is the thing, the lower the degree of the ramp the higher the torque applied to the plates, ie the higher the grip of the plates. (less breakaway)
So it actually is pretty important here, as most people get this backward. They say to themselves well I am getting too much push, (understeer) out of the front end, as a result of the LSD, I must need a lower lockup ramp so they think that say a 20/80 diff might be the way to go, unfortunately, this is completely backward again. They actually need to go to more of a 60/40 instead to limit the amount of understeer.
There is another thing that needs to be taken into account here, and that is the issue of preload. A differential's plates are normally under a specified amount of load at all times. That load is determined by the manufacturer, and can be modified by the end user if you know what you are trying to do.
Up until recently is was thought that a high preload was the best way to get a track car to handle better, as the rear wheels would be locked together until the preload was overcome by the car in a turn. Here is the issue / problem with this mentality. Picture this with me here.
You are running hard down the front stretch of your favorite track. Full throttle, top gear. However at the end of the front straight lies a very tight 2nd gear hairpin turn, not too uncommon these days. Your differential is completely locked up in the straight and you are heavy under braking, and utilizing the deceleration side of the differential to keep your car under control and stable. You go to turn in to the corner, but because the differential is still locked up, you are having trouble getting the car to turn in.
So you think to compensate for this by turning in earlier and shifting to the acceleration side of the differential mid turn. But as you try to do this you notice the front end of the car washing out and pushing your car to the outside edge of the track. (understeering) You manage to keep the car on the track and next time around you decide to take the turn more slowly to adjust for this. Does this sound familiar to anyone? That is okay, you are not the only one, even if others will not admit it. LOL
So what is the solution? Well I have one for everyone that utilizes a Porsche gearbox. And yes, if there are enough people that express interest I can make these for other applications as well.
OS Giken makes a differential that has it's internal ramps counter sprung again each other, which means this. When you are applying torque to the differential on either the acceleration side of the deceleration side of the differential, the ramps spread apart and apply that torque to the internal clutch plates and there by give you your lockup. BUT when you are not on the throttle, or decel side of the differential the springs act to open the differential up, and allow you to turn the car in WITHOUT having to overcome the differential's preload.
So what does this really mean to the driver? Better car control, more grip, and less understeer, less over steer and make your car go. Period. You want to be competitive on the track or even on the street. The OS Giken keeps you sticken to the road. (Sorry had to have a bit of fun with this.)
If you want the competitive edge on the track, then this is the only way to go. (Here is the opinion side of this post.) I have seen several differentials come and go. Some of which I have promoted mostly due to their price point, but this one, I promote because of what it does. This is the hottest differential on the market BAR NONE!!!! I will happily state my reputation on this, if you can find a way to break this, I will replace it for free!!!! OS Giken has never, NEVER seen one of their differentials fail in 9 years. These differentials have been in some of the hottest cars around, mostly in high HP drifter cars, which should tell you something, as these cars are very hard on differentials.
I am not really here to promote the cost of this differential, although I am sure you will be very happy with it, However it would be in your best interest to get one of these before the end of the year. OS Giken has told me that there will be a cost increase after the first.
Look everyone, I can help you with this if you want to get one. I am not the only company that sells these so you can shop around. But please consider this, I am the one that put this information in front of everyone here, you might have never known about this if I had not spent the time to tell you about it. And because of the agreement that we have all excepted with OS Giken, the price is the same to everyone. If you want to know what that price is, then you need to give me a call, so that I can discuss this with you over the phone. I guaranty that you will not be disappointed.
Oh here is one thing that I can offer that no one else can...I will guaranty everyone that purchases this differential a 12 month warranty, as well as guaranty that the first person that can find a way to break one of these differentials, gets one for free. ON ME!! not the company, that is how much I believe in these.
Warmest Regards,
Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell
Feel free to call my cell phone in the evenings everyone, I am always available.
So before I get started here, most everyone knows me from past posts. My name is Erik Johnson and I work for a company that specializes in Porsche Transaxles. We service a wide range of people and applications, including quite a few people here.
There has been quite a bit of talk on some of the other board recently about Limited Slip Differentials, and I thought that some of the information might actually benefit people here, even if you do not have a Porsche transaxle in your car. The information that I am about to write is based on 35 years of company experience, as well as a couple of opinions of my own, so as with most things you find on the net, take it with a grain of salt, as I am sure that there will be some who will not agree with my opinions, and some that will.
So first things first. What does a Limited Slip Differential actually do inside your car? Well it allows both rear wheels to work together to put the HP and Torque of your engine to the ground.
Some of the older crowd will probably still call it Posi-traction, or something similar, but that basic idea is that both rear wheels spin.
In an open differential, only one wheel spins. This can at times be very unsettling to the car, especially if you are trying to put a great deal of power to the road.
In a spool the rear end is locked all the time. This can cause some issues of its own when trying to navigate through a series of tight turns, or worse yet trying to park your car in a parking lot. With both of the rear wheel continuously locked together the inside wheel travels at the same speed as the outside wheel in a turn. One tire therefore, has to skid to keep up with the other in a tight turn. However, when going in a straight line a spool works wonderfully, as the tires will be spinning at exactly the same rate of speed all the time.
Many racers even today like using a spool, even though it is quite tough on the tires, because of the ability to control the rear end strictly with the inputs of the accelerator and brake. If you apply enough power to break the rear end loose, then you can control the direction of the rear end with inputs of both the accelerator and brake, (mostly the accelerator) This was especially fun in the older dirt track cars.
What the Limited Slip Differential brought to the table so to speak, was a blending of both the open differential, and the spool. It offered the ability for both rear wheels, or front too I suppose for front wheel drive cars, to be tied together to put the power down to the road, however, also allowed them to act separately from each other in tighter turns. (Breakaway torque)
Most Limited Slip Differential on the market today are either 4 plate or 8 plate differentials, which means that there are 2 plates per side or 4 plates per side that act like clutches to determine the amount of grip applied to each wheel. These clutches are actuated by the differential ramps which are cut to various degrees, which directly effects the amount of torque applied to the friction plates, and plane plates. These plates are what actually keeps both wheels spinning together.
So LSD 101 right? Here is where it gets interesting. I have seen most people make the mistake of understanding the LSD most when it actually comes to the ramp angles. I will try to explain this the best I can here so that maybe it will make a bit more sense.
A 40/60 differential does not mean 40% lockup on the Acceleration side of the differential and a 60% lock up on the deceleration. This is a common mistake that people make. 40/60 is actually the degree angle that the ramps are cut at. It should be understood that this means 40 degrees / 80 degrees, not %.
So what does that mean? Well here is the thing, the lower the degree of the ramp the higher the torque applied to the plates, ie the higher the grip of the plates. (less breakaway)
So it actually is pretty important here, as most people get this backward. They say to themselves well I am getting too much push, (understeer) out of the front end, as a result of the LSD, I must need a lower lockup ramp so they think that say a 20/80 diff might be the way to go, unfortunately, this is completely backward again. They actually need to go to more of a 60/40 instead to limit the amount of understeer.
There is another thing that needs to be taken into account here, and that is the issue of preload. A differential's plates are normally under a specified amount of load at all times. That load is determined by the manufacturer, and can be modified by the end user if you know what you are trying to do.
Up until recently is was thought that a high preload was the best way to get a track car to handle better, as the rear wheels would be locked together until the preload was overcome by the car in a turn. Here is the issue / problem with this mentality. Picture this with me here.
You are running hard down the front stretch of your favorite track. Full throttle, top gear. However at the end of the front straight lies a very tight 2nd gear hairpin turn, not too uncommon these days. Your differential is completely locked up in the straight and you are heavy under braking, and utilizing the deceleration side of the differential to keep your car under control and stable. You go to turn in to the corner, but because the differential is still locked up, you are having trouble getting the car to turn in.
So you think to compensate for this by turning in earlier and shifting to the acceleration side of the differential mid turn. But as you try to do this you notice the front end of the car washing out and pushing your car to the outside edge of the track. (understeering) You manage to keep the car on the track and next time around you decide to take the turn more slowly to adjust for this. Does this sound familiar to anyone? That is okay, you are not the only one, even if others will not admit it. LOL
So what is the solution? Well I have one for everyone that utilizes a Porsche gearbox. And yes, if there are enough people that express interest I can make these for other applications as well.
OS Giken makes a differential that has it's internal ramps counter sprung again each other, which means this. When you are applying torque to the differential on either the acceleration side of the deceleration side of the differential, the ramps spread apart and apply that torque to the internal clutch plates and there by give you your lockup. BUT when you are not on the throttle, or decel side of the differential the springs act to open the differential up, and allow you to turn the car in WITHOUT having to overcome the differential's preload.
So what does this really mean to the driver? Better car control, more grip, and less understeer, less over steer and make your car go. Period. You want to be competitive on the track or even on the street. The OS Giken keeps you sticken to the road. (Sorry had to have a bit of fun with this.)
If you want the competitive edge on the track, then this is the only way to go. (Here is the opinion side of this post.) I have seen several differentials come and go. Some of which I have promoted mostly due to their price point, but this one, I promote because of what it does. This is the hottest differential on the market BAR NONE!!!! I will happily state my reputation on this, if you can find a way to break this, I will replace it for free!!!! OS Giken has never, NEVER seen one of their differentials fail in 9 years. These differentials have been in some of the hottest cars around, mostly in high HP drifter cars, which should tell you something, as these cars are very hard on differentials.
I am not really here to promote the cost of this differential, although I am sure you will be very happy with it, However it would be in your best interest to get one of these before the end of the year. OS Giken has told me that there will be a cost increase after the first.
Look everyone, I can help you with this if you want to get one. I am not the only company that sells these so you can shop around. But please consider this, I am the one that put this information in front of everyone here, you might have never known about this if I had not spent the time to tell you about it. And because of the agreement that we have all excepted with OS Giken, the price is the same to everyone. If you want to know what that price is, then you need to give me a call, so that I can discuss this with you over the phone. I guaranty that you will not be disappointed.
Oh here is one thing that I can offer that no one else can...I will guaranty everyone that purchases this differential a 12 month warranty, as well as guaranty that the first person that can find a way to break one of these differentials, gets one for free. ON ME!! not the company, that is how much I believe in these.
Warmest Regards,
Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell
Feel free to call my cell phone in the evenings everyone, I am always available.
Attachments
Last edited:
