Leaf Spring Center Bolt Question

[70_Steve]

I'm welding new perches on the rear housing and will do away with the shim. I bought some new 3/8" Rancho leaf spring center bolts and was not impressed, for aftermarket center bolts... The head of the bolt is much smaller than I would have assumed it would be, and the transition from the head to the shank of the bolt is a taper. So I stopped and got some socket head cap screws yesterday but got to thinking about whether there was a really good reason for the Rancho bolts being made the way they are. Oh, and the Rancho bolts are .480 dia and the socket head cap screw is .553 dia.

I need to know what size hole to drill in the new perches. Does anyone have any thoughts on which of these two would be the better center bolt?

 

[toddz69]

I've used the Rancho center bolts in the past without any issues but I'm a bigger fan of the SHCS's as center bolts. They're of sufficient strength and I think the head shape is better for retention in the perches too. One suggestion - get one of sufficient length so the portion of the bolt inside the spring pack is all shank, rather than threads.

I don't have any recommendations for the hole size.

Todd Z.

 

[70_Steve]

Thanks for the quick reply Todd. The springs are older style BC Broncos 11 leaf packs (that I took the bottom leaf out of...). The SHCS most closely matches the original center bolt, except that the original center bolt was all thread. I'm also inclined to go with the SHCS because I know it's Grade8. Not sure about the Rancho center bolt.

I'm moving the differential back 3/4" to give me some extra tire clearance at the front of the rear wheel well. I bought new Anti-Wrap perches from WH, and they came with a 3/4" hole in them for the center bolt. What was I supposed to do with a 3/4" hole??? Good thing I planned on welding up that hole and relocating. I've got no problem drilling the new hole, but with the difference in head sized between the two style bolts I needed to know which one before I drilled.

 

[bronconut73]

The WH center bolts are 7/16's I believe.
That is the biggest ones I have seen.
I just kept drilling my perches until I had a good tight fit.

 

[toddz69]

I bought new Anti-Wrap perches from WH, and they came with a 3/4" hole in them for the center bolt. What was I supposed to do with a 3/4" hole??? Good thing I planned on welding up that hole and relocating. I've got no problem drilling the new hole, but with the difference in head sized between the two style bolts I needed to know which one before I drilled.

3/4" hole? Wow.

Todd Z.

 

[70_Steve]

The WH center bolts are 7/16's I believe.
That is the biggest ones I have seen.
I just kept drilling my perches until I had a good tight fit.

I helped motoman do some stuff that included replacing the leaf spring center bolt. He's running WH springs, and yes, they were made for a 7/16" center bolt. He used Rancho 7/16" center bolts, and they had a nice large head with a square shoulder.

These BC Broncos springs are made for a 3/8" shank bolt. I've got no problem drilling the right size hole in the perch, but have to decide which center bolt to use since there's over .070 difference in the head diameter.

 

[bknbronco]

them rancho ones look pretty cheesey to me as does the rest of the rancho line up. f you drill your springs I hear a concrete bit works the best

 

[CopperRanger]

Try a local sgring shop for center bolts, I needed some a few years ago and they had a ton of different sizes in stock. Plus you could get them with just the right amount of shank and not all threads.

 

[70_Steve]

them rancho ones look pretty cheesey to me as does the rest of the rancho line up. f you drill your springs I hear a concrete bit works the best

Haha!!! Not about to redrill the springs. Need to drill the right size hole in the new perch!

 

[bknbronco]

I was serious about the concrete bit! that was a tip I think I heard from the top bronco builder in the world....Nick. Just thought now was a good time to upgrade the dia if the centering bolt.

You got a .480 and a .553? In my world that's a 1/2" hole and either bolt will work perfect. Once you paint the perches the small one will fit snug and if you sand the bigger one a tad it will also fit perfect. A 1/2" hole is WIN WIN in my book.

Were not building a bar or a liqueur store so a few thousands ant shit.

That black bolt is a machine bolt and probably way harder than some pot metal rancho bolt. I have read numerous threads where guys upgrade to them allen head bolts after destroying the normal centering bolts. Seems imposible but after seeing pics I understand the load placed on that one stuped bolt.

I too will be rewelding perches instead of my 10deg shims when I get around to building and installing my BB 9". And ill be pushing my axle back that same 3/4"

Drill a 1/2" hole and move on

 

[70_Steve]

Try a local sgring shop for center bolts,

Not a bad idea...

 

[bknbronco]

I just measured the hole in my BB 9"perches and they measured 0.600" and 0.550"

 

[70_Steve]

Just called a local spring shop, and was told that all of there centering bolts have a squared off head. No tapers, like that Rancho bolt. We also discussed Grade5 vs Grade8, and his opinion is that the head on the centering bolt is there to initially locate the spring to the differential. The u-bolts do all the clamping and keeping the differential in place. It's only when the torque on the u-bolts isn't maintained, that the centering pin keeps the differential in place and is subject to being sheared. So, either Grade5 or Grade8 should be OK.

 

[bknbronco]

http://classicbroncos.com/forums/showthread.php?t=227600&highlight=centering+pin+bolt+allen+head'

 

[70_Steve]

http://classicbroncos.com/forums/showthread.php?t=227600&highlight=centering+pin+bolt+allen+head'

Thanks for that. I remember the thread now that I read through it. Confirms that the Grade8 socket head cap screw is probably my best choice.

 

[Whoaa]

I'm moving the differential back 3/4" to give me some extra tire clearance at the front of the rear wheel well. I bought new Anti-Wrap perches from WH, QUOTE]

Are there any [known] draw backs to re-drilling the hole on the perch to move the diff hosing back about 3/4"?

I have the same issue, not much clearence on the front area of the rear flare. I was planning to install the WH wrap trap by welding the fitting to the rear diff and then a simple cross member frame. They are currently outta stock on thier war flares, but hope to install a new set of these flexible flares as soon as I can get them.
It seems like, back in the day, many of the rear flares were installed more rearward and people were relunctant to cut the the little brace holding the sheet metal on the forward area of the rear fender sheet metal. I could use all of the clearence I can get for the back tires

 

[70_Steve]

Are there any [known] draw backs to re-drilling the hole on the perch to move the diff hosing back about 3/4"?

Wow! I hope not!!!

I've read here of several members who have done this same thing and not read about any ill effects. Also, it seems like the more people I let know I'm pushing my diff back, the more I find out who've already done that.

Ask me this again in 6 months!!

 

[Rustytruck]

It seems like, back in the day, many of the rear flares were installed more rearward and people were relunctant to cut the the little brace holding the sheet metal on the forward area of the rear fender sheet metal. I could use all of the clearence I can get for the back tires[/QUOTE]

Back in the day people were more worried about locating the flair around the front auxiliary tank filler. They just pop riveted the flair where it fit. This is what kept the flair from moving forward. That and 2.5 inch lift with 31 X 10.50 X 15 tires was a big step.

 

[Crush]

Someone makes rear axel relocation kits with brackets set up for a 3/4 setback or you can flip them for a 3/4 setback. Just cant remember who. Anyone know?

 

[u10072]

If you need to open up a spring use a carbide cutter on a Dremel or die grinder. Much faster and a 1000% less hassle. The SHCS IS THE ABSOLUTE ONLY center pin I would ever use. After seeing them used on a Deaver race pack their use was only solidified in my mind.