Coil Spring Bucket Bolt Specs

[MarsChariot]

Off hand, does anyone know the bolt thread and specs for the two bolts holding the lower coil spring bucket to the axle? I am about to do some work on the front end and thought I might replace those while it is disassembled.

 

[661buster1963]

It’s 3/8 x 16 and 1.25 inch long, many recommend a grade 8

 

[Broncobowsher]

3/8-16 is simple enough. I really doubt the factory were grade 8. It shouldn't be a highly stressed bolt. Think about what those bolts are stressed to, little more than locating dowels. Yes, it is a retainer, but the shock would need to be removed to stretch the axle far enough away to actually pull on the bolt. The shear loads are simply keeping the lower spring from walking around. Anyone saying you need grade 8 is the person who thinks every bolt should be grade 8 and nothing else should exist. Sure you can use them, but they don't need to be that high of a rating.

 

[Steve83]

Ford specifies Gr.5 for most of the chassis & suspension. This table has min/max torque values by size & grade:

(click this text)

 

[MarsChariot]

Most excellent guys. That is what I needed. I am surprised it is only a 16. I thought I remembered it as being finer. But I remember a lot of things wrong, as the wife is pleased to frequently remind me. I did notice that the factory bolt did not appear to be grade 8. Probably grade 5 would be overkill enough.

 

[DirtDonk]

I am surprised it is only a 16. I thought I remembered it as being finer.

Definitely don’t remember it as being fine. But likely the reason you have that in your mind is because it takes so long to remove them when you put a wrench or socket through the coil spring!
A little bit at a time…

That’s why the preferred method of spring removal is simply to loosen them a little bit, remove the upper clamp, and “unscrew“ the spring and remove it.
And then you can get to the bolts easily.

Same for reassembly. Install them most of the way, but don’t tighten them. Screw the spring in and then do the final tightening after.

 

[migs]

Isn’t it actually 7/16-14? I’ve installed quite a few and that’s what I’ve used every time. In fact I include 7/16-14x 1-1/4” long bolts with lock washers and flat washers with my aftermarket coil spring cup offerings and have not had anyone question it yet. Were some actually 3/8-16? I haven’t ran across any like that yet.

 

[jamesroney]

Isn’t it actually 7/16-14? I’ve installed quite a few and that’s what I’ve used every time. In fact I include 7/16-14x 1-1/4” long bolts with lock washers and flat washers with my aftermarket coil spring cup offerings and have not had anyone question it yet. Were some actually 3/8-16? I haven’t ran across any like that yet.

Yes. The Early Bronco is 7/16-14.
Yes, some other arms/caps are 3/8-16, so you can find an oddball once in a while where someone put an F100 cap on a Bronco. Then you end up with both sized bolts.

Yes, the originals are grade 5 with 5/8 hex heads. And yes, I prefer to use grade 8. And no, I don’t think you need grade 8 everywhere.