Technical Pinion Angle & Moving rear end Back

Elton John wants his platforms back! Clucking hell that’s a big block.

Just thinking aloud are you sure the lowering blocks have caused your issue with the driveshaft bottoming out? I’d have thought lowering it that much would have moved it beyond horizontal so despite shortening the wheel base it’ll have counteracted that somewhat by lengthening the distance from diff to box. Is the drivetrain all stock?

 

Elton John joke is hilarious!
I’ve been messing around today to come up with a solution & I believe I have found at least how much to cut things, if I was going to use the old blocks. However, I noticed something a few minutes ago which may move me towards buying new blocks all together and that is the blocks I have are only 4” wide. The ones I had seen at Speedway Motors are 5” wide & checking my perches they are also 5” wide. So going to a 5” wide block would, I believe, help the stability some.

With new blocks I could just add some wedges to the top & bottom of the new blocks to get things correct. I’m assuming a vertical alignment of the blocks is ideal? I really like the idea of making a set of wooden blocks as it would allow me to fine tune things before I bought anything.

 

Use new blocks and/or wedges to raise the rearend vertically not on an angle. It's easy to see why the wheelbase changed with those blocks.

 

Drill a new hole in the block for the spring center bolt head.

Drill a new hole in the spring clamp plate.

You need to make it such that the axle centerline is directly over the spring center bolt, despite the angled block.

If you add wedges or modify the block, you will change the pinion angle.

Personally, I would have new springs made, so you need no block, or just a small one. Your scrub line is currently dangerous. You are a flat tire away from an uncontrolled physics experiment.

 

TRUTH! That scrub line is dangerous and would never pass a inspection in my state. And those blocks? Shit ! A disaster waiting to happen.

 

With the short 4" long blocks stacked that high, I can not imagine the leaf springs do not have cracks in them. Any blocks over 3" high put additional axle twist leverage on the springs, and interfere with the scrub line.

To make matters worse, it appears those may well be the car's original, narrow 2" wide leaf springs. I'm betting the springs are mounted under the frame rails as well. A full redesign of the rear suspension is probably in order.

I would say you have been pretty lucky up to this point to have not had a disaster yet.

 

@HuskerNation , how much power are you running with those skinny springs and tall blocks???

 

If you just have to stay with blocks that tall at least build new lower spring plates. I bent up a pair for a buddy's car where they wrap around the spring with flanges on the side so the U-bolts do not hang below the spring; I also welded the shock mounts on to the plates so they didn't not hang below the spring either.

 

Thats a new style. Old ones are solid .

 

something like this...

 

Appears that grease fitting has been neglected .

 

Be interesting to see the shackle mounts. My 41 chevy when received had tired springs, huge lowering blocks and inverted shackles. The shackles looked normal enough until it became apparent that the spring eye needed to be above the frame mount, not below as might be more normal. Not going to post pics here to avoid confusing the thread. I wonder if that might be whats going on here? Easy enough mistake to make?

Chris

 

My guess is " axle wrap " during braking is pushing the driveshaft forward , contacting the yoke , a total suspension re-do is in order

 

That tall of a block has tendency to break springs and pop out of place under heavy load. NOT A GOOD idea….

 

As noted in all the comments, your current setup is quite dangerous - not only from the scrub-line issue, but all the torque/twist being applied to the springs, etc.. If it was mine, I'd pull the whole thing out (springs and all), checkout the spring hangers (probably redoing them for the stance you want) and you'll undoubtedly need new springs that are designed for the stance you want - without lowering blocks.

Also, you'll probably have to move your springs inward and upward - which will require fabrication work on the frame/hangers and new spring-pads on the axle housing. The right way to modify the axle housing is by somebody who has a big alignment bar and knows how to correctly do the job. The housing will warp when you weld on one side of it (is probably already warped). In many cases the outer bearing ends need to be cut-off, aligned and rewelded onto the housing once all the housing spring pads/brackets/welding work is completed.

Yes, this requires deconstruction, fabrication and welding - but it is the right way to fix this. You'll have a much safer setup and one that will be able to handle horsepower and braking.

 

No kidding. That set up looks undriveable.

 

Wrong! It happens when going over bumps.

 

Are you sure the drive shaft is bottoming out on bumps and the axle isn't hitting the frame instead? Can't be too much clearance between the top of the axle and the frame.

Could be the axle hitting the frame and the driveshaft bottoming out on braking and on bumps.

Either way, everything has to be fixed. Continuing to use it as it is, its just a matter of time before something breaks or get damaged beyond repair.

 

And you know this because you've seen it ?

 

What's the go with the unpainted section of thread on the yoke? Does the screw on cap need to be tightened?
Going by the marks, it looks like the contact isn't extreme.Could the answer to the clearance problem be that simple?
You still need to address all the other issues with the rear suspension setup.

 

The pinion is actually pointing down as shown if we're looking at the driver's side since the block top and bottom locating pin are not in a vertical plane. Is the photo with the car on the ground? If not see where it's at with weight on it.