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Old 10/03/09, 07:05 PM   #1
Joined: Oct 09
Posts: 3

I'm new to the forum. I've just purchased a '76 Bronco. It has 2" blocks over the rear leaf springs. I was going to replace the blocks with an Add-a-leaf. I cannot determine what size U-bolts to purchase from a local hardware store. The present bolts are 10-1/2" x 3-1/4", I think. What size U-bolts do I need to add the Add-a-leaf suspension?
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Old 10/03/09, 07:09 PM   #2
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Blocks BAD!! Add a leafs ride like a rock.. save your pennies and buy a new or used set of springs at the right lift. it will save you a lot of headaches in the future!!

WWW.NORCALBRONCOS.COM 72, TBI 302, 435,20,FW44&9,4.56 w/pl&arb,2" & 5.5" on 37's.SOLD Broncoless for now
Broncos are like BOOBS, There always better after they've been worked on..
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Old 10/03/09, 07:23 PM   #3
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Don't trust the Hardware store U-bolts
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Old 10/03/09, 07:28 PM   #4
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The bronco vendors have U bolts, most of the hardware stores u bolts are not grade 5 or 8, there made for fences and stuff. when U take out the blocks it will handle better, you will gain a little caster and better weaght transfer.
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Old 10/03/09, 07:55 PM   #5
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First of all, Welcome to the site, and congrats on your purchase.

As was said, do not use hardware store u-bolts, bent up all thread or anything close to that. Use u-bolts specifically manufactured for this application.

Second... no offense... but you may as well stay with the blocks, if all your doing is going to the add-a-leaf. Listen to TBS-POPS. Save your pennies, and watch the classifieds on this site, craigslist, and eBay for a set of 2 1/2" lift leaf springs. (i'm going to have a set for sale in 6-8 months..) You will be much happier.

'70 Sport, 351W EFI, NV4500, D20 w/Teralows, 4.56s Dana 44 w/Ox and 9" 31 spline Detroit, 35" KM2's, 3 1/2" lift, 2" body lift, 4x4x2 PS, some other stuff I forgot about...

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Old 10/03/09, 08:01 PM   #6
Joined: Oct 09
Posts: 3

Correction, I meant auto parts store (not hardware store).

I am doing this with the cheaper version to hopefully alleviate axle wrap. If this cures the problem, then in the future I will buy some 11-leaf springs.
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Old 10/03/09, 08:07 PM   #7
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Otherwise, you are correct in your measurements. Inner diameter is 3.25" around the axle housing. Typical replacement is 1/2" stock, but 9/16" is a nice little upgrade. You'll have to re-drill the holes in the top plate (towards the outer edges only, not centered) but, other than that, it's an easy modification.
As for length (measured from the inner I.D. as well), it's up to you to measure compared to what you have now, minus the size of the block, plus the thickness of the add-a-leaf kit. And since you dind't say what block size you have (measured pretty much in the middle usually) or if your springs are original or aftermarket (could make a HUGE difference), it's hard for us to say.
At a guess though, you'll need something in the 8 to 8.5" range. But that's purely speculation. You can always err to the high side, within about two inches or so, and cut off the excess. Heck, you might even find that you can re-use the existing u-bolts if they're in good enough shape. Many of them have enough thread to work clamp down on a smaller load and not run out of thread.
How much thread is left showing below the top plate now?


ps: And a welcome-aboard from me too!!
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Old 10/04/09, 11:32 AM   #8
Joined: Oct 09
Posts: 3
The block measures 2". There is about 2-1/4" of thread sticking above the nuts on the U-bolts. The Add-a-leaf supposedly is going to bump the lift up 2-1/2" inches.
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Old 10/05/09, 12:54 PM   #9
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That's a super stout add-a-leaf!!! A 2.5" leaf is likely going to be pretty stiff, as TBS-POPS was saying. They don't all ride like rocks, but a 2.5'er is probably going to. Depends a lot on the overall condition of the springs too of course, but a single leaf meant to hold the old springs in a new arch of that size is going to be pretty robust.
One way to find out though!!!

On the bolts, yeah, if yours are like most, they're either going to be VERY close to being too long, or they ARE going to be and you'll need those new ones.
Either way though, it wouldn't hurt to have new ones on hand when you start the job. That way you don't drive back and forth during the job. And you can probably return them if you end up not needing them.

For experimentation purposes, my current setup (not driven on yet) is Skyjacker 2.5" springs with 1" blocks and 9/16" diameter u-bolts.
Yes, blocks are the least desireable of the three most common options, but in my case they should work fine and I'll get the ride I want.

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