In The Shop: Easy Does It On U-Joints
Sep 18, 2010
Y'know those little u-bolts that hold the needle bearing caps in the yokes of universal joints? How tight do you suppose the nuts on the ends of those u-bolts should be torqued when installing a u-joint?
I've seen guys use air wrenches to torque them down. I've watched guys stick a big screwdriver through the driveshaft yoke to hold the driveshaft so it couldn't turn while they put all their weight on a 1/2-inch breaker bar to tighten the nuts on those u-bolts.
Pat Fagen, u-joint and driveshaft guru at The Axle Exchange in Des Moines, jokes that when he installs u-joint u-bolts, he puts axle grease on his hand before he uses that hand to hold the driveshaft while he tightens the clamp bolts. "That way the shaft turns before I can overtighten the nuts on the u-bolts," he says.
Fagen explained that few u-joint u-bolts require more than 20 or 30 lb-ft of torque, and that some smaller u-bolts measure their maximum suggested torque in pound-inches.
"If you overtighten the nuts on those u-bolts you can damage the bearing cap and the needle bearings inside," says Fagen. "A lot of needle bearing failures in u-joint caps can be traced to over-tightened u-bolts. All joking aside--when you're tightening those nuts, hold the driveshaft with your (ungreased) hand and torque them to recommended value or till they're good and "snug." There's no need to crank on them till they're good and "tight." Good and tight is probably over-tightened."