By now, most people have seen or heard about the new Super-Flex U-joint from Tom Wood's Custom Drive Shafts. For those needing a review, the Super-Flex is a high-strength 1310-, 1350-, or 1410-series U-joint with the trunions offset 1/4-inch (1410 is offset 5/16-inch) for an added 10 degrees of angularity than its standard counterpart.
The 1350 Super-Flex with standard yokes, 1310 Super-Flex with standard yokes, and a normal 1310 U-joint with severely ground yokes. The Super-Flex joints allow for up to 40 degrees of angle with standard yokes and up to 45 degrees with some grinding.
After installing a 32-spline output Dana 300 in our flattie, we didn't want to compromise on driveline strength. However, our crazy driveshaft angles would not allow the use of standard 1-ton U-joints. And our True-Hi 9 high-pinion, 9-inch rear centersection should not be operated at more than 18 degrees, so a CV-type shaft was out. We had Tom Wood's Custom Drive Shafts build a 1350 rear and 1310 front driveshaft for our rig using 0.120-wall tubing and the Super-Flex joints. Now our suspension can drop out without binding the U-joints, we didn't have to grind yokes, and a spare joint easily fits in our trail kit if we ever do manage to break one.
(From top to bottom) The 1350 Super-Flex with standard yokes, 1310 Super-Flex with standard yokes, and a normal 1310 U-joint with severely ground yokes. The Super-Flex joints allow for up to 40 degrees of angle with standard yokes and up to 45 degrees with some grinding.
Driving Impressions
The Super-Flex joints, while strong, do vibrate. In fact, Tom Wood's Custom Drive Shafts won't sell them unless the customer has been informed of this fact. The company thinks these joints are best used in a front driveshaft application where the hubs can be unlocked on the street. The steeper the angle your driveshaft operates, the worse the vibration is going to be.
Our flatfender is probably the worst-case scenario for this setup since our rear shaft operates at a constant 23 degrees. From a stop to around 20 mph, the vibration is noticeable, from about 25 mph to 45 mph, the vibration is severe, and from 45 mph-up the vibration lessens.
We consider the Super-Flex joints a means to an end. Our T-case is so high and our wheelbase is so short, we really don't have any other simple driveshaft option. In our minds, the increase in simplicity and strength is more than worth the vibration, especially since this is mostly a trail-only vehicle.