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Shop for Slip Yoke Eliminators for your Wrangler TJ or Wrangler YJ at Extreme Terrain!Shop Eliminators
On YJ and TJ Wranglers there is a component called a slip yoke, it allows the rear driveshaft to change length based on height. However, when a Jeep is lifted some problems could occur. A solution that is recommended for anything after 2 inches of lift is to install a slip yoke eliminator and CV driveshaft.
There are two types of joints used on Wranglers driveshafts, a universal joint (Also called a cardan joint) and double cardan joints. The problem with a typical universal joint is that it rotates at a varying speed, this causes vibration and wear due to the constant changes in speed. A constant velocity (CV) joint gets its name from maintaining a constant speed while rotating unlike conventional cardan joint. These CV joints come in many different styles however the most common one for Wranglers is a double cardan joint which is essentially a set of universal joints mounted right next to each other on their own intermediate shaft.
A slip yoke eliminator (SYE) does exactly what it says, it eliminates the slip yoke from your drivetrain. The slip yoke is typically an internal splined shaft that is connected to your driveshaft using a universal joint and transfers power from the transfer case to your driveshaft. It slides in and out of your transfer case allowing it to change length. The rear driveshaft of YJ and TJ Wranglers is a fixed length shaft so the slip yoke allows the driveline to change length in order to account for suspension height changes.
If a large lift kit is installed without changing the driveshaft, the first two issues that occur are that the driveshaft is now too short and the angles are now to extreme for this kind of joint. When you lift your Wrangler you are changing your driveline angles, if these angles are not properly set then your Jeep may suffer from driveline vibrations and possibly wear components like u-joints faster. When the angle becomes too extreme, joint life will be greatly diminished. Another drawback to slip yokes is that if your suspension extends to far it can actually slide out of the transfer case while you are driving/crawling. By installing a SYE you convert the slip yoke to a fixed mounting flange which prevents the risk of your driveshaft from falling out and also allows for a CV driveshaft to be installed.
When the slip yoke slides out too far it runs the risk of falling out of your transfer case, this should never happen with a Wrangler that has not been lifted. If this does happen, not only will you lose power to the rear wheels but the oil in your transfer case will pour out as well. The reason why CV driveshafts prevent driveline vibrations is that they move at a constant velocity unlike a conventional universal joint that constantly accelerates and decelerates as it turns. In addition CV joints are able to be used at greater angles than u-joints, making them great for lifted vehicles.
Realistically, any kind modifications to your Wrangler's suspension can have negative effects on your driveline. If you are considering installing any suspension lift over 2 inches you should strongly consider installing a SYE and a CV driveshaft, however you may be able to get away with a transfer case drop for lifts up to 4 inches. After 4 inches its pretty much required to do a SYE and CV driveshaft. The downside to transfer case drops is that if you try to drop it too much you may need to change out your engine and transmission mounts to get the right angle, and you lose ground clearance which can somewhat defeat the purpose of a lift kit. Installing a SYE and a CV will help ensure that your Wrangler doesn’t experience any driveline vibrations and will keep your driveshaft from being pulled out of the transfer case.
Rubicon Wranglers are a little better in off in that they already have a type of SYE installed from the factory. If you're lifting your Rubicon, the only bit you'll have to worry about acquiring longer driveshafts appropriate to your lift.