Summertime is the season for repairing universal joints on PTO driveshafts that drive mowers, hay conditioners and brush cutters. Whether you use a vise, hammer and socket, or special tool (such as a Tiger Tool Portable U-Joint Press) to repair U-joints, be careful how you reassemble and install them.
“Always listen or ‘feel’ the snap ring click into its groove over the cap,” says Pat Fagen, founder of Axle, Clutch and Gear (AGC) in Des Moines. “If it doesn’t ‘click’ it’s probably not seated right. Then when you connect the new U-joint, be sure the U-joint’s caps are completely and firmly seated between the nubs or tabs in the yoke before tightening the U-bolts that hold the U-joint into that yoke.”
Don’t overtighten the nuts on those U-bolts.
“Tighten them too much and they crush the needle bearings in the caps,” Fagen says. “Car and truck driveshafts only need 17 to 21 lb.-ft. of torque.”
Charts on the internet indicate:
- ½” cap-retaining bolts need 64 to 87 lb.-ft. of torque
- ¾” bolts require 190 to 215 lb.-ft. of torque
Some U-joint repair kits come with lock nuts for their U-bolts. Fagen recommends replacing the lock nuts with standard hex nuts secured with blue Loctite.
“It’s hard to get accurate torque readings with lock nuts,” he says. “With blue Loctite and regular nuts you can torque things accurately and still know that it’s going to resist vibration.”
