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Check your U-bolts!!

paratrooper307 said:
I'm guessing because new vehicles don't use shims. I used the DIY4X shims as well, and one of the side effects is that the spring is angled, therefore so is the top spring plate. This can result in the nuts not tightening down completely square on the plate. You'll have to torque them considerably tighter than factory recommendations, or the differing forces applied will be suceptible to loosening the nuts as the forces of driving act on the axle. I had to re-torque mine periodically after the initial install. Now I check them once a month.
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This is true for the passenger side of a D60 where it has fixed studs in the axle (which DIY4x has a correction for), but on a rear axle this isn't the case. The axle is being rotated, the u-bolts stay in the same position as does the spring plate. DIY4x does mill the center pin recess at an angle so the center pin sits flat and doesn't have uneven stress that you're describing.
 
paratrooper307 said:
I'm guessing because new vehicles don't use shims. I used the DIY4X shims as well, and one of the side effects is that the spring is angled, therefore so is the top spring plate. This can result in the nuts not tightening down completely square on the plate. You'll have to torque them considerably tighter than factory recommendations, or the differing forces applied will be suceptible to loosening the nuts as the forces of driving act on the axle. I had to re-torque mine periodically after the initial install. Now I check them once a month.
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Well, the spring is the same place with or without shims, I believe. The axle and perch just rotate to mate flat with the shim. As far as the spring and top plate are concerned, they don't know about the shim. The only weird thing is that the U-bolts are pulling the perch and shim together at 8* instead of flush. Maybe I'm not thinking that all the way through though.

In any case, I can believe the thing might settle in to find its stable position. Maybe this tend to loosen things up...
 
Mastiff said:
Well, the spring is the same place with or without shims, I believe. The axle and perch just rotate to mate flat with the shim. As far as the spring and top plate are concerned, they don't know about the shim. The only weird thing is that the U-bolts are pulling the perch and shim together at 8* instead of flush. Maybe I'm not thinking that all the way through though.

In any case, I can believe the thing might settle in to find its stable position. Maybe this tend to loosen things up...
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That's the point I was making. If you look at the spring plate when you run the nuts down, the shim causes a slight angle, which is subject to shifting over time, because the front and rear bolts of the top plate connect with the plate at slightly different angles. You can mitigate this to some extent by enlarging the bolt holes, and the expense of potentially introducing a place for slop to occur. Just crank it down nice and tight and it'll be fine.
 
:eek1: I just torqued a shackle flip and DIY EZs and shim under my 'burban along with a 12 bolt. I'm making damn sure I check them often!!!
 
Why not double nut the u-bolts? Use either a jam nut or just get another tall nut and tighten it up on top of the lower ones.
 
100% not meant as a knock on Kert, but I have seen shims split before and then they fall out which leaves everything else loose/broken.

I'm sure his are steel, the ones I've seen split were aluminum, but something to consider.

In our office, we talk about it all the time in regards to aftermarket vs. OE u-bolts. It sure seems like nobody has issues with OE u-bolts, they're set once at the factory and that's it. For some reason, that doesn't translate to aftermarket stuff.

When my Blazer had leaves, I had to tighten u-bolts pretty much every trip, it was a constant fight. Broke a few center pins but only found them while maintaining things, never caused an issue.

My pickup (which gets wheeled but definitely not as hard) has never had the u-bolts come loose. Seriously, install torque and that's been it. I check it all the time and it's always been good, over the course of ~30K miles and probably hundreds of miles offroad.

So I'm not sure what to say, most people have no issues (95%?) but some do for some reason. Our u-bolts are industry standard or better (there are some really bad ones out there), we've kicked around offering a 3/4" u-bolt kit, but that comes with special u-bolt plates in the back and drilling/tapping in the front (assuming GM D60).
 
I was told factory u bolts are stretched during manufacturing. I found this out after replacing factory with aftermarket on my 78 truck. New housing was needed. They came loose a couple of times.
 
ktmoutfront said:
I was told factory u bolts are stretched during manufacturing. I found this out after replacing factory with aftermarket on my 78 truck. New housing was needed. They came loose a couple of times.
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ORD or DIY4x need to get a nice jig set up to pre-stretch their u-bolts then. And charge a bit extra of course. ;)
 
Mastiff said:
ORD or DIY4x need to get a nice jig set up to pre-stretch their u-bolts then. And charge a bit extra of course. ;)
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I used ruffstuffs bolts on my rear axle and they haven't loosened at all yet.

I had a spring shop in town make my fronts and I'm running 5* shims in the front as well, and never had any issues. :dunno:

Maybe different steel used for different u bolts.
 
don't be afraid to crank them is all I say .

and upgrade from stock 9/16" rod to 5/8" rod for much more clamp force and higher tourqe spec . I do it on every one I do .

I have had more problems with cheep lift kit ubolts then factory or good spring shop aftermarket .
 
I used ORD ones before and going with DIY4x this time. I think they are both 5/8" and high quality. Maybe I'll take the air gun to them this time. Is there really any upper limit on torquing them?
 
9/16" was never offered as stock size.

They've all been 5/8" thick.
 
You might be right about the "U" shaped bolts,I too think those were 5/8" factory--but not the squared off ones used on the rears in older trucks,like my '72 K5 had factory...those were 9/16" and I remember having to search all over to find the cast iron "clamp" that goues around the axle tube after one of the ears busted off mine!..I found one ,but if I wasnt able too,I would have had to convert it to the "U" style bolts and buy spring plates..
 
I'm not aware of the '72 and older stuff as I never had an opportunity to inspect and dismantle one.

Everything I've done and learned from was '73 on up and every single one of them in stock form had 5/8" thick rods on both fronts and rears.

Just verifying that fact.
 
Found it

Dan Fredrickson

I guess I should know...But I have some specific thoughts on Ubolts, I put them on like the factory does. You don't bring a new vehicle back after 500 miles to check the ubolt torque, they are meant to stay on*for 50*years. I set the impact to tight and stop when it gets tired...I would guesstimate 125-130ft/lbs...Never had a problem that way,*setting*them to some factory 77-90*setting*just seems too lite and they do work loose, these can take big torque so give them what they want
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Our shims are steel and we've never had one split. I agree with Chris, aluminum shims are bad juju. Run away from them.

That being said, I think the last time I looked at a ubolt torque spec it was 145 ft. lbs.

I think one thing that is critical is getting the ubolt straight and perpendicular to the spring plate, axle tube or whatever you want to go by.

Another thing I think is critical is to bring them all up evenly. Alot of times i've seen one leg of the ubolt tightened much further than the other. That would seem to cause an issue in my mind. The "U" not really on the bottom of the axle but actually partially rotated around the tube.

I believe most of the problems are just not getting them tightened enough initially. After all, we all have a torque wrench. When was the last time you had it checked to see if it was torqueing to the specified value? I bet never. I haven't.

I'll have to dig out a book and see what the actual torque spec is.
 
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