Jeeps with leaf springs in the front have a shackle at one end of the spring pack. This allows the length of the leaf springs to stretch out and contract as the arch of the spring increases or flattens out. Normally the shackle is at the front of the springs, out toward the front bumper. In this stock configuration as the axle moves down and away from the transfer case it also swings slightly back and towards the transfer case. This results in a counter-action and the length of the drive shaft doesn't change dramatically. Doing a shackle reversal flips things around so instead of having a counter-action you now have a double-action.
This usually results in extreme amounts of drive shaft compression and extension, more than normal drive shaft parts can accommodate. This creates a risk of over-compressing the shaft and slamming it into the transfer case or over-extending the shaft to the point that it separates. Either of these scenarios can be catastrophic and can do a lot of damage to the vehicle. This is where our Ultimate Travel drive shaft enters the conversation. This shaft is built using an 11" or longer splined yoke shaft which slides into a splined sleeve in the tube end of the drive shaft.
Not every Jeep with a shackle reversal needs this long of a spline though, usually but not always. For Tom Wood’s Driveshafts to help you determine what type of shaft you will work best for your Jeep you will need to provide them with a couple measurements. You need to measure the distance from transfer case yoke to pinion yoke as shown on their website. Measure at normal ride-height, then again with Jeep lifted by the frame and the axle/springs at full extension. This will give them a good idea about how much extension you need but is not a 100% clear picture. This is because in real life the suspension will move in ways that you can not simulate in your shop or garage. Because of this, they will always want to allow for a little more movement than you measure.
While this shaft works very well, it does have its disadvantages. One is that the shaft is more expensive than one with a more standard type spline. The other is that due to the parts being used it is not possible for them to achieve a good high-speed balance on the shaft. Any shaft built using the Ultimate Travel spline needs to be regarded as a part-time off-road use shaft. Meaning when you are on pavement you need to be able to disengage your hubs and disengage 4WD in your transfer case.
Because of the nuanced complexity of this type of shaft, Tom Wood’s Driveshafts requires that you call them to order it. This is so they can make sure that this is what you really need and make sure it will work well for your application, as well as answer any questions you may have. To order this shaft, or to inquire more about it, measure your lengths as described above then give them a call. 801-737-0757
4 мар 2024
