The Stovebolt Site Forums The Shop Area Driveline Axle perches

Gents, this doesn’t look right to me. I purchased axle perches so I can open my driveline. Do these look correct to you guys? How do I hook U-bolts to it to hold it to the leaf springs?

In the picture is a 3” lowering block with it.

Truck: 1951 Chevy 3100

Pictures from other angles and sides would help.

The axle perches should be offset if you are using the proper ones and if you are using the origional springs .look on the underside and see if the holes are offset .

The u-bolts don't attach to the perch. The perch aligns the axle to the spring and the ubolts go around the axle and through a plate on the other side of the spring.

The bracket has bolt holes that allow it to be offset. That part wasn’t my question. My question was how do the ubolts connect the axle to the springs.

Fibonacho, thank you for that information. I guess I need to find the plate to go underneath.

Chris

A lot of the time new u-bolts come with new plates.

I got my last couple sets at the local spring shop. Bolt and plates together was ~$40 per axle.

Unless you are lowering / raising the height you can just use the stock bottom plate and connect the shocks in the same manner. In that case, the truck and shocks won't know the difference because you won't be changing things by more than a degree or so. If you are lowering the height by 3 inches (as it sounds), that is more than the shock mounting geometry might like. It is all about the angle of operation. You will see GM designed this so the shocks sit at a forward angle of ~33 degrees. I was taught 30 degrees is the optimal range for a pickup. The further you get past 30 degrees is not good because at that point the shock travel is less than the up/down travel of the axle (which you can see would be the same at 90 degrees). With a pickup there are challenges because of varying weight, etc.

Here is my suggestion: using an angle finder app which can easily be put on your cell phone, determine the angle at which your shock absorber will sit after you lower the axle. I think you will exceed 45 degrees and I don't believe that will work.

A friend of mine lowered his (2.5 or 3 inches as I recall) and ended up removing the lowering blocks and going back to stock height because at the lower height the shocks no longer worked correctly and shorter shocks really only repeated the same angular problem for him. What he needed to do was go with shorter shocks and move the frame mount piece to re-establish the original angle.

In my case, I went with stock height and just used the stock bottom plates and had to drill a couple of holes larger since the U bolts were slightly different (because of the diameter of the axle tube). Good luck!

Let’s try this again!

Thanks Jon!

Currently, the only difference is the lowering blocks as I have stock everything (including springs). As long as I don’t change the wheel position, I should still be good. The only change is the height of the axle above the springs. The angle of the shock shouldn’t change with lowering blocks as the shock attaches to the same place/distance as stock (at least with my measurements before and after the blocks.

IF I change the wheel position to center it in the wheel well, you are correct. The shock would be at the wrong angle.

I am going to go look at a shop to see if I can find a plate. It might not be a bad idea to replace the old metal…. (Maybe)

Chris

Plates are easy enough to make. Even a simple shock mount shouldn't be a problem to add.


Didn't see it mentioned and don't want to assume anything, but perches do need to be welded to the axle.

Yes, as long as the shock plate still mounts to the bottom of the springs and if the height of the stack of springs stay the same, all will be Jake. It is when anything changes to make the shock angle larger that you have to start recalculating. I have the formula somewhere in case anyone needs it.

That cell phone app for the angle finder can also be used for determining the pinion angle.

The original plates were pretty thick (maybe 3/8" or so). They ought to be fine. Somewhere I have a digital image or two of what I did but I'm not at my normal computer today and am having to operate completely from memory. I do recall the plate, the shock mount and everything went back with no trouble and I adapted the 1969 parking brake setup to the 1952 with only a slight modification to the part (attached to the frame) where the outer cable mounted.

Update: I talked to Sid at droppedaxle.com and he recommended that I build design a plate to go between lowering block and the spring. He said to drill 2 holes and use 1/2” rod and weld it into one hole to be able to use the blocks.

Going back to the shock location and angle. When the truck is under a weighted load (in bed) the springs depress (?) and the axle centers in the wheel well. If the truck won’t be carrying weight (pop up canopy and little stuff), why would I need to change the angle of the shock if I center it in the wheel well? (I assume that I’d need a slightly longer traveling shock)

Thoughts?

I’m hoping that this thread will help compile info for others in the future.

Chris

Mnsmith,

I have the new perches and that was my original question. I wasn’t thinking about Ubolts around axle… only over perches like stock. They will be welded at the correct pinion angle!

Jon,

Thanks, I’ll be playing around a bit more once it warms up in TX. My garage heater just died!

Chris

Hi Chris,
Sorry...I thought you were considering lowering your truck but now I see you already did that. Couldn't you just use the lower plate (under your leaf springs) to continue connecting your shocks? I finally found an image of what I did. This is an image taken while lying on my back. It shows the stock lower plate along with the shock mount (which in my case bolted to the plate separately). Hope this helps.

Yes, I could do that! Thanks Jon.

I know there was some confusion earlier, so I drew up diagrams so every understood. Again, trying to help others in the future. My diagram does not show a plate under the springs (ops!).

Chris

Hopefully this doesn’t confuse anyone!

This what I did on my '59. I added Traction Bars and used those as the lower spring plates. The lower shok mount is also on the Traction Bar. You may just need a simple Spring Plate like used on a trailer axle.

Thanks Tut, I almost have everything I need to complete the the job. Trying to ensure that I’m good to go before I take my truck apart and can’t get it back together!

Chris