By far the most under-rated modification to a vehicle is the addition of a Limited Slip Differential, assuming it doesn't already have one. It seems there are a lot of people who aren't bothered about fitting one, and as far as I can tell, it's because they can't see it once fitted and just want more power.
I get it, they're not cheap but you can't deny that traction makes you faster than any big turbo setup.
If you want to leave your pal in the dust and not be in it, you simply need one. Spinnin' ain't winning. Well, unless you're doing a sick ass burnout, which LSD's are great for because it will lock both wheels, not just spin one wheel. (usually occurring on transverse engine/gearbox arrangements)
What does a Limited Slip Differential do?
Jason Fenske describes how a Limited Slip Differential works through his YouTube video that is linked below.
In case you are in school, work or a cupboard hiding from your children and can't watch the video, I'll briefly explain.
Essentially, a differential is an arrangement of gears that splits the 'power' (kinetic energy) from the gearbox to the wheels. Instead of just having a solid shaft between the two wheels, a differential will allow each wheel to turn at different speeds, significantly better for handling and tyre wear.
A Limited Slip Differential has the same function but is designed to do exactly what it says in the title; limit slip. aka. the slip (or excessive spinning) of the wheels. On an open diff, it will follow the path of least resistance, prone to wheel spin straight off the bat. An LSD will do the opposite, it will favour the driven wheel with the most traction (most resistance if you will). Depending on the type of differential, it will use helical gears or plates/clutches to send torque to the wheel with the most traction.
An additional benefit of having a Limited Slip Differential is improved braking, due to the LSD locking, increasing mechanical drag which also reduces the amount the brakes "lock", keeping the ABS system happy.
"Once installed, drivers will notice an immediate difference, as the Quaife (ATB) limited slip differential automatically biases the torque across the axle to the wheel with the most grip. Unwanted wheelspin and slip are greatly reduced, resulting in less understeer on front or four wheel drive machines and reduced oversteer on rear wheel drive vehicles. Rear wheel drive cars with a Quaife limited slip differential become more controllable during oversteer moments, enabling drivers to exploit the full potential of their machines for the first time, leading to a more exciting, rewarding and rapid driving experience."
- Quaife
Types of LSDs
ATB (Automatic Torque Biasing)
ATB differentials are maintenance free and aren't noisy like Plated differentials due to the gearing being helical rather than straight cut. One negative of an ATB is if you lift a wheel, it will act similarly to an open diff in that it will spin. But if you're lifting a wheel on a street car, you should really be looking at your suspension setup.
Plated
We've covered above that Plated diffs aren't maintenance free, use straight cut gears so are noisier but they will lock regardless whether both wheels are on the ground.
Which type of Limited Slip Differential should I choose?
Easy. Road car: ATB, track car: Plated.
ATB diffs are maintenance free, plated diffs are not. ATB diffs don't have clutches, ramps, springs or other wear prone components to replace at regular intervals.
We only tend to list the ATB differentials on our site at this moment in time, if you require a plated limited slip differential, please contact us.
How an LSD is fitted?
In a transverse arrangement engine and gearbox layout, the differential is fitted within the same casing within the gearbox. On something like a MK5 Golf, you are looking at an 8-12 hour installation time. The gear oil must be drained, gearbox removed from the car and opened up to remove the OEM differential. The crown wheel must be removed from the OEM differential and placed onto the LSD, (most often with ARP hardware), replaced into the gearbox, sealed and refitted onto the car and filled with gear oil.
Visual demo
So now you should have a bit of an understanding of LSD's, you should watch the video below for a visual demonstration.
You should clearly be able to see the benefits from this video alone. The driver experiences a lot of wheel spin and understeer which is detrimental to the lap time. If you are someone who likes taking their car to the track, an LSD is an essential part for your vehicle.
The Weigh Up
Pros |
Cons |
| Traction | Expensive |
| Sick burnouts | Not easy to install |
| Reduced understeer | Some LSD's require maintenance (non-ATB differentials) |
| Improve track times | |
| Increase cornering speed | |
| Reduces tyre wear | |
| Improved braking |
Put your ego aside and buy an LSD. I assure you it will be one of the best purchases you make.
Take a look at our Quaife products here.
If you do not see a product suitable for your vehicle, please get in touch and we will be happy to find the item you require.
If you have any further questions about purchasing or installing a Limited Slip Differential, please do not hesitate to call us on: 0114 276 8193 or email us at: info@jbmperformance.co.uk
