Should Thread Locker be Used when Installing Trailer Suspension U-bolts

Question:

tandum axels and leaf springs were replaced by shop. axel u bolt lock nuts came loose after 1700 miles causing rear axel to shift and blow a tire! should nuts be replaced? should locknuts should have been used? should I double-nut? should locktite be used? Help!!

asked by: JT

Expert Reply:

Lock nuts alone should have been fine but you could use some Loctite, # LT37614, for extra protection. Make sure to use the blue Loctite and not the red version. The red would make it very, very difficult to remove the nuts.

Since you mentioned the lock nuts failed then I recommend replacing not just the nuts but the u-bolts as well. The threads could have been damaged on the u-bolts so it is better to go ahead and replace them. I have included a link to our trailer suspension u-bolt main page for you.

Also make sure the nuts are torqued down properly. For 1/2 inch u-bolts torque them to 45 to 70 foot pounds. For 9/16 inch go to 65 to 95 foot pounds. And for 5/8 inch they should be 100 to 120 foot pounds. They should not back out using Loctite but be sure to check the torque values after 1 or 2 trips.

expert reply by: Michael H