Why are lift blocks bad news?

[colinrmitchell]

So everybody agrees that lift blocks on a front axle are bad.

What, then, is the cause of this?

My first guess is that, since front driveshafts are generally shorter than rear driveshafts, axle wrap creates a harsher angle on the driveshaft, and hence the U-joints.

Is there something that I'm missing? What do you all think?

 

[adsm08]

for the same reason you can't put re-treads on the front of a taxi in PA. I dunno what that is, but I bet they are related.

 

[brendank]

For the same reasons that they are bad in the rear, plus if a block were to come out, you'd lose some or all steering capabilities.

 

[lil_Blue_Ford]

The larger the block, the more leverage an axle can exert on leaf springs, which equates to axle wrap.

Axle wrap is when a spring loads with torque, in other words you could think of it as the leaf spring taking on an S shape instead of the normal downward bow. That exerts a lot of force on the driveline and usually results in snapping things if it is severe.

I'll have to see if I can find it again, I used to know of a good site that explained it all in detail with pictures, but that was before my other computer succumbed to the infamous blue screen of death.

Basically blocks on rear axles are bad news. Blocks on front axles can result in even worse problems (like losing your steering).

At least in PA it is illegal to use any sort of lift blocks on the front axle (this includes the 2" coil blocks, but the F-150 spring perches hit on a technicality since they are not classed as lift blocks).

 

[85_Ranger4x4]

Just about all Ford 4x4's have lift blocks on the rear from the factory, I have never had a problem I could blame on them.

In the front I would be more worried about the front axle peeling back weird under hard braking than anything, the rear axle doesn't see near the load in that situation. As far as wheel hop goes, my F-150 burns them straight and true

 

[bigcountry]

i would be more worried about a block shearing in half like in a corner or if you were to hit a big bump. thou i have only heard that happing to aluminum lift blocks

 

[Shran]

Front leaf springs can bend and even break, especially offroad. This is with no block. The added axle wrap with a block in there would multiply the problem and you would be looking at broken springs, broken steering, driveline, etc...not something that should ever happen offroad much less on the highway.

FWIW, there is nothing wrong with blocks in the rear as long as you don't over do it (4-5" IMO) and DO NOT STACK THEM. Leaf springs in general will load up and axle wrap is always going to be a factor unless you add some kind of anti-wrap device.

My F150 has no blocks and the rear springs will load up like crazy.