Practical Automotive Maintenance: LSD Friction Modifiers
Watch This Course
$99 USD
-OR-
Or
8 easy payments of only $12.38 USD
Instant access. Easy checkout. No fees.
LSD Friction Modifiers
04.23
| 00:00 | In our previous module on oil specifications, we covered all types of differential oils and how to choose the right one for our car. |
| 00:08 | In this module we'll dive deeper into the specifics of friction modifiers as well as when or why they might be necessary if you're using an aftermarket LSD. |
| 00:17 | Some, but not all limited slip differentials or LSDs require friction modifiers to ensure smooth clutch pack engagement and proper operation. |
| 00:26 | For those that do need it, using the correct modifier is essential to ensure quiet LSD operation and smooth engagement. |
| 00:33 | There are three common types of LSD we're likely to come across. |
| 00:37 | Viscous, clutch type and helical. |
| 00:40 | And it's only the clutch type differential that requires friction modifiers, so that's what we'll be discussing here. |
| 00:47 | These LSDs use gears, clutch packs and springs to manage torque distribution. |
| 00:52 | The operation of the clutch packs generates friction and heat. |
| 00:55 | Using the incorrect oil can cause excessive wear and uncomfortable driving experience with potential binding. |
| 01:03 | This is where friction modifiers come in to optimise the clutch plate's friction properties, preventing chatter, clunking and binding during low speed turns while ensuring proper torque transfer. |
| 01:14 | This not only improves drivability and control over wheel slip, but also extends the LSD's lifespan by reducing wear. |
| 01:21 | The requirement for a friction modifier depends on the specific design of the LSD. |
| 01:26 | Some brands use clutch plates that are engineered with specific friction materials or surface finishes that are intended to run without extra modifiers. |
| 01:34 | Others are deliberately designed to need a certain amount of modifier blended into the oil to stop chatter. |
| 01:40 | Many aftermarket LSD manufacturers offer their own LSD oil which already contains the required additives. |
| 01:47 | In addition, many LSD specific oils such as Motul Gear Competition and Castrol Syntrax LS already contain the right additive package. |
| 01:56 | In these cases, no extra friction modifier is needed. |
| 01:59 | So, what exactly are the friction modifiers and do we need to add them to our differential? If we remember back to the oil specifications module, we mentioned an extremely effective and popular anti-wear additive called ZDDP. |
| 02:12 | This additive is used alongside molybdenum disulfide for friction reduction while phosphorus and sulfur compounds aid in maintaining proper lubrication in high heat and pressure situations. |
| 02:24 | There is a vast range of different organics and synthetics used in diff oils, but they all share the same goal of allowing the correct amount of slip, lubrication and anti-wear properties to ensure long life and optimal performance. |
| 02:36 | Some LSD manufacturers will specify the use of a base oil with the addition of a friction modifier on top. |
| 02:43 | This allows the amount of friction modifier to be tailored to the specific requirements of the LSD and the application. |
| 02:49 | Stacking friction modifiers on top of an oil that already contains these can reduce the clutch's ability to lock, defeating the whole purpose of the LSD. |
| 02:58 | In addition, this can also result in overheating and ultimately clutch damage. |
| 03:02 | So, assuming we have an LSD which specifies the base oil plus an additive, how do we know when we have enough? Generally, when there is insufficient friction modifier, we will experience symptoms like clunking and binding during tight, low speed turns. |
| 03:17 | If this is the case, then it's time to break out the additive. |
| 03:20 | We can start by adding a small amount, around 20 -30ml at a time. |
| 03:25 | And once this is done, test drive the vehicle and see if the symptoms improve. |
| 03:30 | It's critical to ensure the correct type of friction modifier is used and using the wrong type can lead to improper operation and potential damage. |
| 03:37 | This will be specified in the owner's manual for your LSD. |
| 03:42 | After each addition, monitor the performance of the LSD. |
| 03:45 | If the chattering or noise persists, we may need to add more. |
| 03:49 | Let's quickly summarise the key points from this module. |
| 03:52 | LSDs come in several designs, viscous, clutch and gear types, but only the clutch type requires a friction modifier. |
| 03:59 | These additives ensure proper clutch function, control torque split between the wheels and provide correct lubrication and heat management. |
| 04:07 | Some differential oils are formulated for LSDs and already contain modifiers. |
| 04:12 | If the manufacturer specifies a particular oil without recommending extras, adding more can actually, harm friction control and slip. |
