I don't think the problem was so much with the blocks as with the ubolts. What you found is what I thought had happened. You can see in the photo where the front of the block is sitting on the outside of the perch. I've seen it before when ubolts aren't properly tightened. The blocks will start to walk around and hammer on the perch.

You may be able to salvage them, but with what you're looking at in using a wider spring, replacement is probably the best option. That way you can fix the pinion angle without using shims, which are in a way just low-rise blocks. That said, I used shims with my Alcans, and all is well.

Know anyone in a machine shop? Have new blocks made out of solid bar stock and mill them to the angle you wish to have. You could go with the new perches welded at the desired angle, but if ever convert to a different setup you will be in the same predicament as far as angle is concerned.

That makes sense. Interesting too in that they hammered their way down on the perch and no longer walk around.

As to the angle/shim vs. welding the perch at a different angle issue, I'll give that some thought. I'm hoping that
the chevy spring mod will be the last rear suspension mod. (Laughing while typing).

I do have access to a milling machine as well as a friend with one, so I can get wedges as needed.

The considerations for me are whether to have the rear of the truck torn apart for that much longer while wedges are made or weld in perches at the needed angle and then add wedges on later mods. I'll probably end up doing the modifications sometime this winter.

Walk is probably a bit of an exaggeration. "Pace back and forth?" When the axle tries to wrap it causes the block to want to rock forward and back on the perch. You can see where it did it on the rear of the perch before it decided to sit forward - the sides are more rusted where the block abraded the metal. I'm surprised you never felt it. When mine started to do that the increased sensation of wrap was really noticeable.

With the gap at the rear grown to what it is, I might start being a little concerned about the block spitting out unexpectedly. It's probably not so well seated on the front of that perch to hold it in if you really stress out the rear end. Be gentle with the stupid pedal til you fix it.

Thanks for the advice. I was starting to think about the block being loose and what all could happen. I think I'll try putting a temporary plate in this weekend just to keep it from flying out while I gather the spring swap parts. My main worry is that the ubolts aren't actually all that tight now that the block has squashed down over the perch. That too would make the block more likely to spit out as you say.

Ironically the whole reason for the spring swap was due to what felt like huge axle wrap. It may have been the block weirdness.

Looks like I"m taking the car today. :-)

I just measured the tube diameter under the spring perch and it's approx. 3.25". Is this right? I thought I saw 3.5" somewhere and was wondering about buying the proper perch.

Thanks in advance.

Chip

I would go for welding new perches in at the angle you have now for your setup. Get solid blocks made that are wide and long enough to have the u-bolts go through them rather than around them. You should have enough clearance for the brake lines and such. Make the blocks "square" and, if you decide to do it again with a new setup, make appropriate blocks.

Those perches look perfectly fine from what I can see in the pictures. The blocks just look like they don't fit (too big). Maybe they were for a domestic truck application that has wider springs?

Get a block that fits, or build your own out of box tube. If you build new perches, build them out of box tube as well. 2.5" square with 3/16" or 1/4" wall works well and is a common size. Don't use solid. :p

Some I made a while back:

Thanks for the suggestion. The perches may be salvagable. They are kind of mashed up on the front which isn't too visible in the picture. I'll look some more and see how bad they are.

I looked at the situation some more and had further observations. The angle of the drive shaft is totally off. There is a u-joint coming out of the transfer case, the drive shaft has the double cardan joint in the middle and there is a u-joint into the diff. As I understand it, the double cardan is a "cv" joint and doesn't figure into the angle determination. However, the two u-joints at the ends do, and the shafts should be parallel. This is not the case, so I'll have to right the problem.

Eric,

Do you know the diameter of your axle housing? Is it 3 inches or 3.1 or 3.25? I measured 3.25 (sort of) and see 3.1 and 3.0 inch diameters on the web.

Thanks for your help and advice and thanks in advance.

Chip

How about using a piece of string and using C=2(pi)r? Might help confirm the measurement you took. <img src="/forums/images/graemlins/kewl.gif" alt="" />