MTFCA Forum

How much wear is too much on a u-joint before it is worn out?

By Ford specs, if more than .006" it's scrap.

Don't forget to pack the u joint area with a light grease.

Kerry wrote: ↑

Sat Dec 14, 2019 1:41 am

By Ford specs, if more than .006" it's scrap.

Frank is right on; Ford Model T Service, paragraph 591, "If there is over 0.006" clearance between knuckles and rings a new universal joint should be installed."

The rear axle booklet that is published by the MTFCA on page 17 says "The four bearings should also be tight with no more than 0.010 - 0.020 inch clearance."

While doing the most recent rear axle overhaul I was fortunate enough to have a N.O.S. Ford universal joint and the clearance was 0.0025" to 0.003" depending on which trunion/knuckle you would check. There is quite a discrepancy between the Ford specification and the MTFCA booklet, 0.006" versus 0.010" to 0.020" of clearance. If anyone has a new replacement/reproduction universal joint on hand, I would definitely be interested in knowing what the new manufacture ones are coming in at.

And Larry is right, don't forget to pack the u-joint bell at the front of the driveshaft housing, prior to re-installation. After I would run a newly installed u-joint (rebuilt rear axle) for a little bit, I would always add some more grease. The spinning and centrifugal force will spin out some of the grease and create a void in and around the u-joint, pack it back through the grease cup.