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 | Driveshaft travel, from full spring compression to full spring extension, is also an issue that will need to be addressed. With arced springs, as the springs compress, if nothing else happened, the driveshaft would have to get shorter. But, as the springs compress, shackles will swing away from the differential. Again, if nothing else happened, the driveshaft would lengthen. As it is, the two things work in opposition to each other and the driveshaft will have a relatively stable length. The extent of travel on an existing application can usually be determined by looking at the wear pattern on the spline stub from the dust cap on the slip yoke.
There are many configurations to which the above principle does not apply. Most notably, a front shaft with a shackle reversal. In this situation the two normally compressive and | |
| extending actions are now working in tandem. This will cause the driveshaft to compress and extend substantially more than it would otherwise. Additionally if you have flat springs, the driveshaft will tend to compress only minimally but extend substantially. A special note to you YJ owners with a shackle reversal - make sure you have enough room for the driveshaft to compress (get shorter). Salvage yards are doing a great business in 231 transfer cases, replacing those which have broken because the front driveshaft was driven into the case on the road or trail. It's prudent to at least try to simulate the full range of movement for the driveshaft through the extent of suspension travel to make sure your driveshaft meets your needs.
Breaking the driveshaft or U joints can be the result of a number of different causes. Assuming that you're not having one of the problems outlined above, the first thing you may want to look at is the quality/strength of the components themselves. Original equipment driveshafts are not built for ultimate strength. Typically, the tube will be the weak point on a factory shaft. When you are having a new driveshaft built or an old shaft reworked, increase the tube diameter, wall thickness and grade of tube used. The cost differential will be minimal in the short run and the potential savings, for the long haul, will be substantial. | |
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