8 3/4 housing U-bolt torque
- Thread starter Duster_71
- Start date
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I think it's 40 ftp but it's been awhile .
It's either 40 or 45 LB FT. It's nowhere near as tight as you think, because the springs need to be able to flex. If you over tighten the U bolts, the rear suspension will pound you to pieces.
This is from 70 service manual. Suspect 71 would be the same
famous bob
mopar misfit
Nothing to do w/ the original post, but all wheels do not take the same torque. Weld wheels recommends 95 pounds for the draglite, and prostar wheels. If u run them at 65 , u might be having to tighten the every run or so .
mopowers
Well-Known Member
Do the spring leaves actually slide relative to the other leaves at the center of the spring between the two halves of the u-bolts during the springs range of motion?
They slide at the ends as they arch and de-arch. (for the lack of a better term) The center bolt keeps them aligned in the middle. Because the leaves are arched, they lengthen as they get flat and they do slide. That's why there are pads on the ends of the springs. Because Mopar springs are quite short on the front section most of the sliding happens on the rear section.
mopowers
Well-Known Member
That's how I understand it as well. So how does over-torquing the U-bolts cause a stiff ride then?
I wonder if the housing moves around a bit in the u bolts. I know that if you overtorque the u bolts you can dent/ distort the axle tubes.
mopowers
Well-Known Member
I figured that was the reason for the relatively low torque spec. I never quite understood how over-tightening the u-bolts would make for a rough ride. To me, there'd only be two way- either it makes the spring bind, or it increases the spring rate. I just don't see how either of those could happen.
Torque them to 100 LB FT and get back to us.
Mrpatel
512Dart
I just installed my Caltracs and mono leafs and they wanted 75 - 80ftlbs. I torqued them to 75 and I can feel the threads and bolts stretching. I found the factory torque spec in my manual somewhere. I think the guys above are correct with 40 - 45.
Mopar-Man
Big Block Better Burnout
New 1/2" u-bolts???
Some new U bolts are not flat on the inside. This puts a point of pressure on the housing (greater PSI) where the U bolt contacts the housing tubes. Too much pressure and you might crimp the tube. Factory had the area of contact on the U bolt flattened applying much less PSI to the tube.
Mrpatel
512Dart
Nope, is that a must? Calvert racing never mentioned anything or best practice.
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Streetsboro Rick
Well-Known Member
Torgued mine to a 100
Streetsboro Rick
Well-Known Member
Found that spec on an old chassis's manual I believe
69_340_GTS
Well-Known Member
Make sure the weight of the car is on the axle before you torque the nuts to 40 ft.-lbs.
It's incorrect.
Ya I tightened mine down with a 1/2" impact and let her rattle until I found out I was doing it wrong!
Streetsboro Rick
Well-Known Member
Very possible it was an old one
Streetsboro Rick
Well-Known Member
Also never collapsed a housing or had au bolt come loose
Mrpatel
512Dart
I am going to order a new set after reading the thread. Calvert sells 1/2” grade 5 7” long for $35.00. Thanks for the post. Andrew
mopowers
Well-Known Member
If the reason the torque spec is only 40 lbs is to let the leaves slide, why does it matter if the weight is on the axle when you torque them? Won't the leaves still slide at 40?
69_340_GTS
Well-Known Member
I dunno. Do whatever you want... That's just the correct way to tighten them. It's standard practice for anything with leaf springs.
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