secondler

I bought a second hand 2016 xlt and it came with a chain padlocked to a tie down in the box. After 2 months and 2000 km finally met back up with the previous owner to get him to remove the chain and lock. I thought a rattling noise from the rear was the chain but it persisted after the chain was removed.

I found that the axle u bolts had backed off about 1/2" and the rattling noise was the U shaped cup under the axle bouncing around. I'm not sure what was even holding the axle on to the truck other than the driveshaft and shocks. I feel really fortunate to not have had an accident.

I went out and bought a torque wrench and 7/8th deep socket (rear has a 1.5" lift so probably not stock u-bolts) but the nuts had a lot of resistance so it was taking more than the 98 ft-lb of spec'd torque just to move them. I cleaned and greased all the threads that were showing and had to use a breaker bar to get them started and some of them got easier.

I thought the torque wrench would slip when it was at the desired torque but apparently it was a click-type, and it would click just to turn the nut at all before it was even near tight so I didn't pay any attention to the clicking.

Anyway I tightened these u-bolts up as much as a physically could with a 2ft torque wrench thinking it was going to slip ... and it did slip for a couple of nuts, but maybe because it was way over the setting of 98 ft-lbs.

The good news is the rattling went away, as well as a bit of a clunk when shifting from neutral in to gear.

It doesn't seem like I should be able to damage the axle by over torquing but I am worried the U-bolts might be compromised by all the rattling and now being way over-torque. I've read they shouldn't be re-used and this seems like a re-use since they went from tight (presumably) to loose and back to tight.

Any insights greatly appreciated.

Crimson

I would definitely replace those U-bolts. Maybe the previous owner had blocks stacked to increase the ride height and got into a pickle with the way your describing how hard the nuts were to turn and just let it slide or whatever. Anyway you are correct in saying the U-bolts are supposedly a 1 time use and your's do seem to be stretched..

Eddiegt

Rolled bolts I always toss out. I never trust to reuse. They tend to stretch out after torque.
I think the new bolts are only around $50
I am going to do a add a leaf and I can't believe some suppliers recommend reusing u- bolts.

tmcolegr

on another note...

Please tell me you didn't use your torque wrench as a breaker bar to continue to try to tighten the nuts after the torque wrench had already clicked or use the torque wrench to loosen the nuts. If that's the case, the torque wrench is most likely damaged and is no longer accurate.

mikeinatlanta

Have yet to see anyone prove that appropriate levels of torque on U-bolts will permanently stretch them. Torque is too low for that so reuse is perfectly fine, normally.

However, yours is a special case. Your bolts came loose with indicates an issue, so replace the bolts and nuts. Your nuts have an unusually high running torque required to run them down indicating damaged threads, so replace the U-bolts and nuts. You torqued beyond the limits of your torque wrench, so replace the U-bolts, nuts, and most importantly your ruined torque wrench. Lastly, buy some beer for someone you know who is a bit more mechanically inclined to help you and double check your work.

Gillie Dog

Yep, replace U bolts and nuts.

As for the torque wrench, the local auto parts stores will loan you one (at least around here they do) so you can compare torque from it to yours and see if they match.

GD

tvsjr

Considering the number of yahoos who have likely had their hands on said torque wrench, I wouldn't trust it to be any more accurate than his already-questionable wrench!

Wrenchbender

You said you greased the threads,did you also grease where you were going to Torque the Nut if so that's why you couldn't get to the desired Torque with Lubed Threads you already over torqued those nuts,you don't use a lubricant when you torque your Lug nuts or these U Bolt Nuts,Its called COF Coefficient of Friction look it up.

UNBROKEN

iTrader: (1)

Threads are galled and trash...replace all the hardware and torque to spec. You’ll have to cut the old u-bolts off if it’s as you said and the nuts wouldn’t even spin.

Masi1926

I agree with them. It's an inexpensive replacement that's worth the peace of mind.