Help on rear blocks?

[franklin2]

Seems very over engineered, I personally would just ditch all blocks and do all spring or shackle flip lift. Shouldn’t need a traction bar if you have decent springs


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I have never used the shackle flip, at first it sounds like a great idea. But then you hear reports from people who have used them that it moves the rear wheels forward in the wheel wells, and also messes up the pinion angle requiring pinion shims to correct it.

Lift springs can be good, but they are expensive and I wonder if they are progressive like the factory springs? I like my factory ride empty.

 

[79jasper]

Them powerstroke guys have been doing traction bars/ladder bars for awhile.
Supposedly ride quality stays the same.

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[fyrfghter]

I have never used the shackle flip, at first it sounds like a great idea. But then you hear reports from people who have used them that it moves the rear wheels forward in the wheel wells, and also messes up the pinion angle requiring pinion shims to correct it.

Lift springs can be good, but they are expensive and I wonder if they are progressive like the factory springs? I like my factory ride empty.

Yea you would most likely need to adjust pinion angle with either shims or new spring perches. If you mock up the shackle flip and don’t move the front spring hanger the wheel should not move forward or back.

It’s all personal preference, I do a lot of 4x4 stuff with my truck so I am building it for performance, if you don’t want more wheel travel etc then I would stay as close to stock design as possible.


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[u2slow]

I have never used the shackle flip, at first it sounds like a great idea. But then you hear reports from people who have used them that it moves the rear wheels forward in the wheel wells, and also messes up the pinion angle requiring pinion shims to correct it.

Lift springs can be good, but they are expensive and I wonder if they are progressive like the factory springs? I like my factory ride empty.

Those shackle flip problems can be prevented by lowering the fwd hangers, i.e. keeping the leaf spring level. That's how I did mine.

I had rough country 4" leafs in my F350. I thought the rears rode okay. The fronts were the rough ones.

 

[Alwaysreadyrob]

Can someone explain what Axle Wrap is and what flipping the shackles does ? 1 have a 1994 f250 IDI t and its 4x4.
And a 2002 F 350 PSD 4x4

 

[laserjock]

Axle wrap is the torque of applied to the axle to twist the pinion upward. The occurs because the leaf springs allow the twist. The wheel hop occurs because the springs will only twist up so far before they stop and then the wheels break traction unloading the springs and start the cycle again causing it to bounce.

 

[snicklas]

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[towcat]

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For reference here are stock 250, 350 and then the SD lift block. This one from procomp.

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Better picture of the angle. This caused me problems. Empty it was barely noticeable until I was looking for it. Loaded it was pronounced due to the torque causing axle wrap and shoving the pinion farther up out of alignment. The pinion was actually angled backwards when pulling.

I too have broken traction exactly one time and I really thought I had broken it. Holy wheelhop Batman.

for an OEM ride height, the SD block is way too steep. Check out this thread on pitching driveline angles.
https://www.oilburners.net/threads/pitching-driveline-angles.55946/#post-654142

 

[franklin2]

Can someone explain what Axle Wrap is and what flipping the shackles does ? 1 have a 1994 f250 IDI t and its 4x4.
And a 2002 F 350 PSD 4x4

If you go back and look at your rear leaf springs, the front of the springs has a single bolt going through to hold them to the front bracket, but the rear of the springs has a single bolt that goes through a short piece of metal or what they call the shackle. Then the shackle has another bolt going through it and through the frame bracket.

So the rear of the spring is not directly connected to the frame, it goes through the shackle first. This is so the spring and grow and shrink as it goes over bumps in the road.

If you notice, the rear of the spring is above the frame shackle mount. These kits they have turn this around, so the spring is below the frame/shackle mount. This lowers the spring down, which raises the truck frame and body up.

In the stock configuration, when you put a lot of weight in the bed, the weight tries to stretch the shackle longer, putting the metal of the shackle under tension. When you use a shackle flip kit, when you put weight on the truck it will try to compress the shackle. I have never thought this was a good idea, but apparently people have used these kits with no problems yet.