How to Check Driveshaft U Joints? | Measure The Play

A worn U-joint rarely announces itself. You get a clunk when shifting, a vibration that builds with speed, and eventually a driveshaft that lets go on the road. Catching it early starts with knowing how to check driveshaft U joints properly — the whole test takes about ten minutes, needs no special tools, and comes down to one number:.006 inch.

The steps below follow the service procedures Dana/Spicer publishes for driveline U-joints and the method BMW uses for front and rear driveshaft checks. Set the vehicle up correctly, and the actual test takes a couple of minutes per joint.

Checking Driveshaft U Joints: What The Hand Test Tells You

The hand test tells you whether a U-joint has wear you can’t see. You grip the yokes on either side of the joint and try to force movement that shouldn’t be there.

Put the transmission in Neutral and release the parking brake first. Then raise the vehicle on a hoist or a pair of jack stands so the drive wheels rotate freely — this is not a job for a bumper jack.

Before touching the joints, look over the whole driveshaft for foreign material buildup, dents, damage, and missing balance weights. A shaft caked in mud or bent from an impact can vibrate exactly like a worn U-joint.

Then test each joint. Grip the input and output yokes with both hands and try to twist them in opposite directions. Hold one yoke stationary and move the other vertically and side-to-side. On a healthy joint, the yoke feels locked in place — no clunk, no perceptible movement. Similarly, check the slip yoke where it leaves the transmission by moving it vertically and side-to-side.

BMW’s service procedure runs the same check in quarters. Hold the flange and test radial play, rotate the driveshaft 90 degrees, and repeat until the shaft has turned a full 360 degrees. If no play appears, move on to inspecting the needle bearing seals on both front and rear joints.

How Much Play Is Too Much?

The limit is.006 inch.

The figure comes from Dana/Spicer’s commercial driveline service documents, so treat it as the benchmark for the joints covered there rather than a universal number for every vehicle on the road. For anything else, check your shop manual first. Either way, the movement you measure has to come from the joint itself. Play measured at the frame, axle, or transmission housing is often just normal flex, and it will send you chasing a false reading.

A joint can also look perfectly healthy and still fail the test. If the movement exceeds the limit, the U-joint is the problem regardless of how fresh its grease looks.

What Else To Inspect Under The Driveshaft

Beyond the play test, every joint needs a complete visual inspection. Dana/Spicer’s SPL U-joint service guide is specific about what to look for: damaged bearing retainers or stamped straps, loose strap bolts, loose companion flange bolts or nuts, loose or missing spring tabs and bolts, damaged tangs, damaged or missing snap rings, and bearing cups that rotate in the yoke.

On driveshafts with a center support bearing, inspect it for looseness, broken rubber mounting, and heat damage — the rubber isolates the bearing, and when it splits, the bearing takes the abuse. Dana/Spicer’s guidance is to run this inspection every time the vehicle comes in for scheduled maintenance, not just when vibration shows up.

Nothing in this job requires a guess. Support the vehicle, run the hand test on every joint, and treat.006 inch as the line between fine and failed. Any joint that crosses it gets replaced before it strands you on the road — and if you’re picking parts, our tested U-joint driveshaft roundup covers the replacements worth your money.