The Stovebolt Site Forums The Shop Area Driveline '54 3100 rear end question

My apologies up front if this is stupid question but, I need to ask it. I recently pulled the bed out of my ’54 Chevy 3100 to work on the bed sills and remove the aftermarket fuel tank the previous owner installed. However after doing the work I noticed something strange. With the truck in [u]PARK[/u], if I grab hold of the side of the bed and rock the truck forward and backwards (just the inch or two that it’ll allow) the entire rear end pivots up & down. Rock the truck backwards and the nose of the differential housing noticeably raises up. Rock it forward and nose dips down. This is all while the driveshaft is still in place. I’ve worked on cars as an enthusiast for decades, and honestly, the only time I’ve dealt with a rear end is while the vehicle was up on a lift, or jack-stands. And I’ve never worked on a rolling chassis. So this is the 1st time I’m viewing this, from this angle, under these circumstances. I don’t know if this is “normal”. I thought the rear end never moved and if it did it wouldn’t be this noticeable to the naked eye, and the U joint was there to handle any movement (?). I should also note, the previous owner also lowered the truck. I’m not sure whether or not he removed one (or more) leafs from the rear springs. If so, is it possible he just might not have tightened back up the U-bolts that secure the rear end to the springs properly? Hence, allowing the entire rear end to rotate slightly?
Again, maybe this is a whole lot ado about nothing, but seeing this is a 1st for me, so I wanted to try and get some input from the forum. Thanks in advance for anyone’s input/advice. John

Can you see the u-joints?

If you can, you have a modified rear-end and rear-suspension.

Yes, you're correct Tim, this isn't a stock set-up. My apologies for not clarifying that in the orig post. The entire drive train has been modified. Camaro front clip up front and I have no idea where the previous owner got the SBC, tranny & rear end from. I guess my question was just a general inquiry, not specific to a particular make/model. Should a rear end move as much as I described? Can video’s be posted to the forum? If so, I can try to take a real short one to show folks. Thoughts/comments? Thanks for your reply Tim! John

The short answer is the rearend should not move like that. Something is wrong with the way it is mounted. A video or photos can be loaded onto one of the hosting sites like Photoshop and then a link to it posted here.

Are the spring perches welded. Stupid question maybe but I just have to ask. I know what happens when they are not! Are the "U" bolts over the rearend tight?

Hi all, thanks for the feedback!
The U-bolts were the 1st thing I checked as well. They’re tight. Frozen is more apropos. But there’s no play/movement. I thought he might have removed a leaf and didn’t tighten things back up, but I wasn’t able to get any movement from around the U-bolts or the springs themselves. Also, the rear end is not moving within the bolts (if that makes any sense). The top of the “U” is very much in contact with the rear end and moves when the rear end moves.
The spring perches are bolted, not welded to the frame.
Here is a quick video I just shot…

I can't see the springs or perches in your video.
You state that, "The spring perches are bolted, not welded to the frame." Spring perches are normally welded to the axle.
Can you take another video, but pan out so we can see at least a complete view of one side?
Carl

Hi Carl,

Sorry about that, I was fixated on an issue I found on the shackle bracket last night. My bad. OK, the perches. To the untrained eye, it looks like he used wrong size perches. They are welded to the rear end WHERE THEY MAKE CONTACT, but looks like the perches on there were meant to accommodate a larger diameter rear end. There is a slight gap at the top of the perch on both the front & back side.
They also don’t look like they leveled prior to welding. There’s a noticeable gap between the base of the perch and the 1st leaf.


What I was looking at last night were the shackle brackets. Those are bolted to the frame, and I noticed something cracked on the driverside rear!


Since I’m vetting all my issues (found so far) with this truck, I was a little taken back by the position of the shock tower mounts on the frame. I (personally) have never seen shocks mounted at such a drastic angle before. Have any of you?


Thanks again to all for their input & advice!
John

Whew what movement, I hate to say but the spring perches look awful flimsy to me. They clearly in video are home made and the material looks sub-standard. Material not with standing they are not welded completely and what weld is there I would suspect as to its quality or if it is not cracked.

But in watching the first video over again several times, while I may be wrong but it looks like the far side axle tube is moving in the housing.

The shackle bracket is broke and must be replaced.

If it was me I would start with a unbolting of the U-bolts, finding a proper set of perches and weld them on.

I think the shocks would not be very effective at that angle. That perch does not seem to be firmly mounted on the axle or the spring.

Had to watch that video again, check the plug welds on the axle housing for the axle tubes.
If they look good, I would still chalk mark the tube and the housing and do the rocking.

You have a very unstock suspension in your truck.the rear spring hangers are not the stock, the shocks have been moved from outside the frame to the inside. All this to allow for lowering the ride hieght. Note the C notches in the frame.also the springs are not stock width.nothing wrong with all that, worth knowing that as you work on it down yhe road. And yes your problem is with the perches not being secure. Note the rust around the u bolts and mounts. Cut it all off weld on new perches and don't reuse the U bolts, always go new.also make sure the pinion angle gets set right. If it is not , you get a vibration from the ujoint.

Thanks. The truck is sitting too low in my opinion. The front suspension "I assume" is a case of dropped spindles put in, but I was trying to figure out what he did to the back end and more importantly, how to change it. I knew the shocks were messed with, but I couldn't determine where they actually should go be mounted. More homework to do

I would redo the spring perches..you can buy them from spring shops..new u bolts and replace tthe rear spring hangers.and if you want to raise your ride height, 2 ways to do that...reposition the rear hangers or put a spacer block between spring and diff. That will change the shock angle considerably. My 54 has stock suspense but upgraded diff and the rear shocks do have a forward angle but not that drastic. Also suspect they were put inside the frame as the diff is to narrow for the shocks to stay out side the frame. If you want them back outside the frame.... you'll be looking for a wider diff. Hope that helps.

I can not see the count of leaves in the springs but looks like it may be shy a few setting ride height a bit lower and softer. count the leaves.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0459.html

Also a stock set up on the 3100 for perches is much different, with the perches installed as in pictures you likely see about a inch drop in the rear from that setup.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0456.html fig 86.

Last possible drop is in shackles, if the space between bolts and pin get smaller the ride goes lower.
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0454.html

I'm going to recant my comment on using a spacer block to increase ride height.that only works with diff mounted under spring.yours is diff on topnof spring. Really the only choice is to reposition rear hanger so the top of hanger is closer to or below bottom of frame, which will be a challange as it appears that the front of spring it mounted outsde of the frame as well. The original suspension was attached to the bottom of the frame.