How Wrangler Clutches Operate & Upgrades

1997-2006 TJ Wranglers with a manual transmission either came with an Aisin manufactured AX5 unit or an AX15. The AX5 transmission was installed in TJs with a 2.5L engine and is considered a light-duty manual transmission. As such, it is not particularly strong and is easily overwhelmed when pushed in an off-road, high torque situation. It mates to an 11-1/4" clutch (9-1/16" organic disc) and diaphragm spring pressure plate.  

The Aisin AX15 model is a medium-duty transmission that is used in TJ Wranglers equipped with the AMC 4.0L inline-six engine and is quite robust. In fact, it is considered by many to be the best factory 5-speed manual transmission ever installed in a Jeep. It is mated to a 12-1/2" clutch (10-3/8" disc) organic compound clutch and diaphragm spring pressure plate.

2007-2017 Jeep Wranglers did away with the Aisin transmission and instead were offered with a newly designed by Chrysler NSG370 transmission. This is a 6-speed transmission that also uses a 12-1/2" organic clutch to transfer the power from the engine to the wheels. The new 2018 Wrangler JL switches back to an Aisin built manual transmission - the AL6. Clutch size has been upgraded to an​ 11-1/8" unit.

From the TJ all the way up to the latest 2018 JL, all manual transmission equipped Wranglers use a hydraulic clutch setup. Here's how it works. When you depress the clutch pedal, hydraulic fluid is drawn from the clutch master cylinder and displaced towards the slave cylinder, which is secured to the transmission with one end entering the bell housing and resting on the clutch fork. Because fluid is not compressible, the force of you moving the clutch pedal down is transferred to the slave cylinder, where the fluid then extends a rod. This rod pushes on the clutch fork, which slides the throwout bearing (clutch release bearing) away from the carrier and into contact with the pressure plate. The linear force of the throwout bearing presses the diaphragm spring of the pressure plate and in turn releases the clamping pressure on the clutch disk. At this point, the engine has been disconnected from the transmission. Releasing the clutch pedal causes the hydraulic pressure to drop, causing the slave cylinder to detract, the throwout bearing to slide off, and the pressure plate to once again mechanically press the clutch disk to the flywheel.

Surprisingly, the stock LUK clutch that Jeep Wranglers are equipped with usually last a pretty long time and are even known to survive an off-road smoking or two. Nonetheless, the time will come where the friction material is just too glazed or worn out to effectively transmit power. When this happens, you'll be stuck with the decision of going with an OEM replacement or an aftermarket upgrade. What exactly does the aftermarket have to offer, and is it any better? Let's find out.

'Stage' clutch kits: Aftermarket clutch manufacturers often designate their clutch kits as a stage 1, stage 2, or stage 3 upgrade. All of these designations are relative to the holding capacity and thermal capacity of the stock clutch.

A stage 1 clutch system will be similar to an OEM clutch but with a little more holding capacity. Engagement, friction material (typically organic or a hybrid), clutch life, and overall feel will remain the same however it will be able to hold more torque.

A stage 2 clutch kit will build on the prowess of a stage 1, being more aggressive and with even more holding capacity. The clutch disk may be fully lined (entire surface is covered with friction material) or feature many smaller puck areas. Friction material is often still resin-based but may be blended with additional metallics in order to produce more bite. Spring pressure will increase as well to give a stage 2 more holding capacity. The result of all of this is a clutch kit that holds a significant amount of torque over stock but for the most part is still very streetable. Clutch life, on the other hand, will be slightly diminished.

Stage 3 clutches are reserved for high horsepower, high grip applications. These clutches use almost exclusively a blend of metal, ceramic and/or kevlar as their friction material, which provides an extremely strong grip. The downside is that streetability suffers, as these clutches tend to have an 'on-or-off' feeling associated with them. In terms of a Wrangler, this type of clutch functionality is not desirable for any street or trail going Jeep.

Another type of clutch that appears on the Wrangler aftermarket is called a dual-face or dual-friction clutch. This type of clutch features a different friction material on each side of the clutch which enables a type of hybrid operation. Frequently, the flywheel side of the clutch is a segmented-puck style, which is ideal for increased loading per inch, but less ideal for driveability. Then, the other side of the clutch will feature a full lining with a slightly less gripping material, which balances out the aggressiveness of the puck side. The result is a clutch with a high holding capacity, smooth engagement, and no chatter.​

Most clutch kits come with the clutch disc itself and at least a matching pressure plate. More complete kits also include a new flywheel and throwout bearing. While a new flywheel is not needed (as most of the time the original can be machined by a proficient shop), a new throwout bearing is cheap insurance. In fact, JK Wranglers are notorious for having their throwout bearing go bad, which leads to a lot of noise when the clutch pedal is not depressed. Furthermore, you may want to consider replacing the slave cylinder as well. It is often seen that a slave cylinder will suddenly fail after a clutch change due to the new pressure of the clutch.

Replacing the clutch on your Wrangler is certainly a big job, but it can safely be done at home with the appropriate tools. The biggest obstacle is getting the Jeep high enough off the ground that the transmission can be easily dropped, and then having a support for the transmission as it comes down and another support holding the engine once the transmission is out. Dealing with the exhaust can be tricky too as the bolts and studs are prone to rusting in place.