I put a 9'' out of a 59 Ford in my 66 FB. While I was at it I put in new leaf springs, spring plates from a 69 Cougar and New 7/16 u-bolts with grade 8 flat washers under the nuts. I did a search and found one that said torque the nuts down to 45 ft. lbs. Being an overkill person I went ahead and went to 50 ft. lbs. When I finished I was looking at them and noticed that the u-bolts were turned outward slightly at the bottom. The spacing is correct at the top. What is the problem or problems? Did the extra 5 lbs. of torque, cheap u-bolts or spring plate flex do this? Is this to be expected or should I change u-bolts or what? Any suggestions or ideas will be appreciated.
REAR SPRING U-BOLTS
- Thread starter danny clemens
- Start date
atomicpunk
Member
Mine did that, especially the inside rear bolts on both sides. I'm not terribly worried about it, but I will keep an eye on them.
I can tell you now that 50 ft/lbs aint nearly enough.
I tighten them with a long 1/2 breaker bar till I can't turn em no more. And that's somewhere north of 100 ft/lbs. You do NOT want them working loose somewhere down the road, and at 50 ft/lbs, they will.
Also use good quality grade 8-9 lock washers in additon to the flats. When you're done cut off any excess threaded portions ( over about 3/4" long past the nuts)
I tighten them with a long 1/2 breaker bar till I can't turn em no more. And that's somewhere north of 100 ft/lbs. You do NOT want them working loose somewhere down the road, and at 50 ft/lbs, they will.D.Hearne said:I can tell you now that 50 ft/lbs aint nearly enough.
U bolts are ment to stretch and are generally made of a softer metal. Because of this I would be very careful about how you torque them down. They can be over-torqued..it happens quite often. In fact, the guys doing my alignment after lowering the 70 gave me a hard time about my rear U-bolts being overtorqued (they wanted to replace). And I can tell you there is no way I got anywhere near 100ft/lbs into those nuts. All I used was my 1/2" ratchet and a little muscle..I could have easily tightened them more without picking up the breaker bar.
302 coupe
Founding Member
I'm with DHearne, I've had 'em come loose before and it was very unnerving. Now I torque 'em real good, go for a drive, then torque 'em some more. No way I'd leave leave them "finger tight" at a mere 50 ft-lbs. You need to make sure that the u-bolts are straight up/down and not angled. If the holes on the spring plate won't allow this, you need to enlarge the holes.
The only U-bolts I've ever had break, was just a couple months ago on the 2005 Pete I drive. NONE of the one's I've ever installed myself ever broke. And I torqued the crap out of every one. I HAVE seen lots of other's U-bolts come loose. Did they come loose from being over torqued ? I seriously doubt it. More likely they weren't torqued enough to stretch them in the first place, and they stretched in service and worked loose. If I were you, I'd go back and put a breaker bar on those you did and see how much you can turn them now.70_Nitrous_Eater said:
Thanks for the input. The u-bolts were straight up and down before I torqued them. I even measured them. Maybe the Cougar spring plate is too wide because they used a different setup than Mustangs. They had a rubber pad, a wedge and another metal plate I think. I'll have to recheck everything and then I might have to change the spring plate.
krash kendall
Active Member
I don't think I've ever had of u-bolts NOT bend when using original plates. And when using new heavy-duty springs always go back and re-torque every other day for a week untill they settle enough so you can't see daylight between the spring and plate.
I think the problem is the spring plate flexing letting the u bolt bend out. I got the spring plates off of my old 8" and they have a curved lip all the way around and not just on the side like the 69 Cougar plates have. I'm going to weld the original holes closed and redrill to fit the wider axle housing bolts. I hope this takes care of the problem. If not I'll just torque 'em down tight and let it go. Good idea to tighten them down after use.
atomicpunk
Member
Flex-A-Form warns against torquing the U-bolts over 50lbs, so I did it to 50lbs on the nose. I thought it was strange most of the U-bolt kits only come with flat washers. If them coming undone is so common, is lock-tite a good idea?
krash kendall
Active Member
atomicpunk said:
They come loose when you don't periodically re-torque after installing new springs for the first week or so. They tend to not "flatten out" between the pad and plate when first installed and will settle over a breif time driving.
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