What lowering blocks?

[frank88]

My Mum is travelling to the US in a months time and I was going to get her to bring me back some lowering blocks as they are hard to get here.

 

Does anyone have a link to some 3" blocks they've used? Thanks.

[G-Duax]

A word to the wise, if you plan on driving the truck hard, or have made power improvements,

FORGET blocks !

They put a hell of a strain on the leaf springs due to the leverage the axle gains on twisting the springs.

I snapped two leaf springs using them.

 

Find some flatter springs from the 4wd 720 (??)

Mike would know more on the ones I've seen people use.

[datzenmike]

Hell make your own!

 

 

 

Go to scrap metal dealer. Find some 3" by 2.5" (outer measurements) by 1/4" steel box section and buy two 6" lengths. (3" by 3" by 1/4" would likely be easier to find and will probably fit between the U bolts) Drill a 3/8" (or what ever is suitable) hole down through the middle. 

 

 

The leaf spring pack has a pin holding them together with an extended knob, or pin, at the  top that seats into the spring perch to locate it (above) and keep it from sliding around against the U bolts. A suitable nut and bolt head will do. Your blocks are going to fit in between and need a pin or bolt head in the top to fit the spring perch hole and on the bottom a hole to fit the leaf spring pin into. Bought ones are exactly the same but perhaps the ends of the blocks are welded closed.

 

 

Measure your U bolts and buy new ones that are longer by what ever the block is tall. This comes down to drilling a couple of holes the rest is turning a wrench.

 

BTW these are actually 2" 620 lowering blocks that I used on my 710.

 

 

[frank88]

Sweet, cheers for your input both. I'll make my own then 

[datzenmike]

Beforehand you wil probably notice an increase in vibration. or low frequency rumbling. This is because the drive shaft angles have changed relative to each other. If so report back later

[frank88]

Will do, need to get it running properly first. Haven't touched it this year, been renovating the house.

[G-Duax]

To cure the driveshaft issue, raise the center driveshaft bearing about 1" with spacers, and longer bolts.

[G-Duax]

Here is a picture to show you what axle wrap up is:

It gets worse the further the axle is moved away from the leaf springs.

And also radically changes the angle between the centerline of the drive shaft, and pinion gear.

So, at least add traction bars......

 

[distributorguy]

A traction bar that's available off the shelf will actually be very dangerous on a 3" lowered truck.  If you ever have a flat tire, it will contect the ground and spin the truck out.  You're better off finding a spring shop who can build you a new upper leaf spring that's a bit stronger than original, and reverse the spring eyes to get you an extra 1 1/2" lower with no other mods.  Then you can use a safer, shorter lowering block.  Around here its about $100 a spring set for a rebuild plus a new upper spring.  In the process they can dearch the pack for you.  

[Stoffregen Motorsports]

Right. Doing things the right way is often less expensive than one would think.

 

[Ben_upde]

Spring under has less leverage on the pack than spring over. This is because the bulk of the rotational prevention strength is in the main leaf, which is also the upper leaf. I would much rather run a 3” block on top of a spring than below. 

I had first hand experience when I did a Spring Over Axle swap in my Wranger I had. V8, 5 speed, plenty of tire shredding power. Never had a single glimmer of axle wrap or hop when the spring sat under the axle. Moving the spring on top of the axle caused so much wrap and hop that I had to make an anti-wrap bar to keep u-joints in it. Same spring pack. Just mounted differently. 

Moving the axle upward in relation to the top spring is much less prone to wrap than moving it downward. Plus, with the power range of these things, good luck getting axle wrap even with lowering blocks. 

 

On Topic, I purchased my blocks and U-bolts from Oreilly Auto Parts. They came with 2° shims to correct pinion angle. Cost about $45 for everything. 

[distributorguy]

12 hours ago, Ben_upde said:

Spring under has less leverage on the pack than spring over. This is because the bulk of the rotational prevention strength is in the main leaf, which is also the upper leaf. I would much rather run a 3” block on top of a spring than below. 

I had first hand experience when I did a Spring Over Axle swap in my Wranger I had. V8, 5 speed, plenty of tire shredding power. Never had a single glimmer of axle wrap or hop when the spring sat under the axle. Moving the spring on top of the axle caused so much wrap and hop that I had to make an anti-wrap bar to keep u-joints in it. Same spring pack. Just mounted differently. 

Moving the axle upward in relation to the top spring is much less prone to wrap than moving it downward. Plus, with the power range of these things, good luck getting axle wrap even with lowering blocks. 

 

On Topic, I purchased my blocks and U-bolts from Oreilly Auto Parts. They came with 2° shims to correct pinion angle. Cost about $45 for everything. 

 

I'd have to guess when you raised your truck by going axle-under-springs you didn't have straps around the springs.  That would have eliminated most of your axle wrap by using ALL of the springs as a traction bar, instead of only the shortest ones.  Normally, only the front of the springs would be strapped, but the rear is where you'll experience lift issues and axle wrap with the axle under the springs.  My truck has close to 200 hp at the wheels and with a rebuilt spring pack I have no discernable axle wrap.  If I did, I'd build the caltrac style traction bars Duax posted above, as that setup actually increases downforce at the rear wheels by utilizing axle wrap to add traction.  

[datzenmike]

 

 The leaf springs in the 620 (and the 521) are quite robust and are not known for axle wrap problems even lowered. Removing a leaf to lower (never do this) or replacing the engine with something with much more power might though if you have some 'sticky' tires on it and poor shocks. The L20B just doesn't have the power to do this. Best to just be aware of what it is and how not to cause it.

 

I would measure the drive shaft angles and correct it properly and exactly, rather than blindly throw in any shims provided.   

[distributorguy]

There's nothing blind about raising the center/carrier bearing on the driveshaft when you raise the rear axle.  Its line-of-sight.  Since the truck can't axle-wrap, you have 3 degrees (or more) of flex in where the pinion angle can land.  In essence, since you're not changing the pinion angle by raising the axle (moving it in a parallel plane) you shouldn't even have to check it.  The driveshaft will however "dip" in the center if you don't raise the carrier bearing, putting more stress on the U-joints.  Duax was right about that.  Our race truck drivehsaft sits level, and we had to raise the carrier bearing 1" to do that, using custom springs and 1 1/2" blocks.  

 

[datzenmike]

Didn't say that. Said throwing on a correction leaf spring shim without first measuring the angles is going into it blind. You're assuming some manufacturer knows better than you. Do you put new plugs in without checking the gap? Set the valve lash cold assuming it will be good enough when hot? So how do you know that 1" was perfect without measuring it???? It looked good??? ?

[distributorguy]

Didn't say that.  I'm saying I sorted through it and check pinion angle, which did not change throughout raising or lowering the the rear end, or when I lifted the huge "kink" out of the center of the driveshaft.  Normally the carrier bearing is supposed to reduce the driveline angle by half.  If you can place it in a position to reduce all U-joint angles, its doing its job.  My worst U-joint angle is 2 degrees from straight.  No vibration on the chassis dyno at 204 mph.  I'd say that's proof enough that we're in good shape.  And yes, I "eyeballled" it - with a 4' construction level and a cheap magnetic angle finder from China Tool (aka Harbor freight.)   My whole point is that the pinion angle was correct to start, and it didn't change throughout the process.  

[datzenmike]

Well... good. I used a protractor and a string with a washer. ? It was repeatable and good to the thickness of the string. A 1/8" thick shim on the back side of the spring perch tilted the pinion down just the right amount. Still can't believe 1/8" made such a difference in ride.

[distributorguy]

If you buy the "better" lowering blocks, they are cut with a taper to correct angle changes.  ?

[frank88]

Where would I get those from? The Oreilly ones come with a shim and are $40 (cheers Ben). They need to be picked up from store though ?

 

In short, why is this a bad idea:

 

 

(Pic stolen from Oukippy)

 

 

Or are you saying i could just flip my leafs over and get them dearched which in itself drops me an inch or so, plus a 2 or 3 inch block and job done?

 

Sorry, I'm very new to leaf springs, they are quite different to coilovers!

Edited September 20, 2018 by frank88

[distributorguy]

You don't flip them over.  You get a spring shop to make a new top spring, and they fold the bushing eyes the other way so that it lowers the truck.  Depending on how much you want to lower the truck with the spring, they can make the spring shorter in length, so that the rear shackle still has room to function, rather than resting against the frame.  You can't completely change the direction of arch without making the spring wavy and weak.  In the end, you can go lower yet with blocks if you wish, but you'll have to C-notch the frame as the springs alone can nearly run you out of room for suspension travel if you go far enough.  

[2wheel-lee]

2" to 3" blocks are no problem with all the springs present - especially with the stock engine. This has been done for ages without problems.

 

Sure, manipulating the springs by a reputable spring shop may be better, but blocks are sufficient (an unreputable shop will cause nightmares).  Depending on how low you want to go, 720 4x4 spring packs will lower the truck about 1-1/2", so that and blocks may be a good, easy combination.

 

NOTE: If you're installing them like the pic above, make sure to cut the U-bolts. You should never have any part of the truck lower than the bottom of the rim (larger rims help). 

[frank88]

Thanks for all in info here, gives me something to think about. Not sure how low it needs to go yet until I think about wheels