The Stovebolt Site Forums The Shop Area Driveline Torque setting: front axle spring Ubolts

Since I’m replace front leaf springs. I can’t find the torque requirement for the Ubolts that hold the axle to the springs or how tight the front shackle (name?) bolts should be. Previously, I think I over tightened them and destroyed the rubber bushing/seal.

Thanks

Chris

Ps I prefer to use something more specific than 2 grunts of torque.

In the text for spring and u-bolt installation in the service manual, it just says "tighten securely", but I just found the torque specs on page 4-48 of the 48-51 Service Manual.
Rear U-bolts: 1/2 ton 75-90 ft lb, 3/4 thru 1-1/2 ton 210-235 ft lb, 2 ton 375-400 ft lb (sure glad I don't have a 2-ton ) I went with 100 ft lb on my 51 3100
Front U-bolts (page 3-13) same on 1/2 ton, 3/4 ton thru 2 ton 125-150 ft lb.
I didn't find shackle bolt torque, but I think 25 ft-lb should do it. Again the service manual says "tighten securely", then says smack the shackle arms with a hammer and retighten.

Thank you! I missed that when I looked! My brain is all over the place right now.

Chris

I missed that part. Might need to get the BFH out and do some smacking!

If it were an import pickup would you need to use a metric hammer?

No but you'd need to torque the shackle bolts to 34 newton meters.

Proper torque = 1/4 turn before you wring it off.

My computer is old and acting up so no copy and paste, just google search u-bolt torque. Most all the spring manufacturers have charts on their web sites. Torque values are for the thread diameter, doesn't matter what they go on. 1/2"-20 u-bolt for example, torques to 52-70 ft lbs depending on if its oiled, dry, or plated. After some drive time, they need a re-torque.

if you can wring a "U" bolt off with a 3/4 inch wrench, well thats doing something. Tighten the best you can,
drive it and tighten again.

I've used the "torque it till it breaks and back off 1/2 turn" technique a time or two. I have broken 1/2-inch bolts while torquing them with a 2' lever arm torque wrench, but a 3/4 hex combo wrench would be a bit more than I could do.

OP - Be aware that almost all axle u-bolts are torque to yield, and should not be re-used. Although probably millions have been reused without issue, personally I'd get new ones and torque them according to the fabricator.

Some useful info attached.

Geoff - For some folks that find having to download a PDF like this troublesome or difficult, I've captured each of the 4 pages of the document as pictures and attached them below for easier viewing.

Thanks for sharing this information! The safety aspect is definitely a good point to bring up.

Interesting and useful information there. Never throw away your old U bolts before laying them on top of the new ones.

I just found that 1/2 ton is 90 ft/lbs…. Not 120 ft/lbs like I thought.

Years ago I pulled the front end apart to remove leaves from the front springs. I installed new U-bolts at that time. I don't remember the torque I used but probably a 7/8 socket with a 3/4 drive breaker bar with a length of pipe on it. Years later I would like to take is apart but using the same tool set up, I can't get it to budge. I was stronger when I assembled it... then there's rust. So this time I'll probably just cut them off with the torch... After the new springs come.