Technical Rear end setup on my ‘48

I would unbolt the shocks and drive it again with weight in the back or bounce on it when it's on the tires, then put a couple of adults in the back and try it again. Do you feel the shocks stopping it. Anyway I do see newer springs and shackles in your future, maybe try to find a good used kit pair.

 

I too think think the shocks are bottoming out. Unbolt the bottom shock bracket and drive around the block to see if it is better. It also looks like the pinyon angle is not correct, there are posts on here about that. Cut the axle brackets off and fix the centering and pinyon angle. Make longer shock mounts so you can use longer shocks. With the mistakes made mounting the rear end I wonder about who mounted the MII. It might be camera angle but the front wheels apear to be too far back in the wheelwell. If the same guy did both ends I suspect the front is screwed up too.

 

If you are going to re-mount the shocks, I would prefer to see them angled side to side, not front to rear as yours appear to be. Seems like the OEs all mount the bottom of the shock low on the axle and tilted in about 15 or 20 degrees toward the center of the car. With a car the size of yours, that would also help in the side to side sway.

my 2 cents. Maybe not worth that much.

.bjb

 

There is lots of wrong going on, the shock angle is funky and may be bottoming out on the up-stroke. The springs look tired considering there is a lot of leafs to it. Now it comes down to how good your fab skills are or how deep your pockets are, although sliding a new spring kit into it and the labor is not astronomical. I agree on the front tire not being centered in the wheel opening.

 

Ok, morning update: Armed with all of your input, I took on the car and... fixed the gas tank. Well it was a win at least.

Also, interestingly I got it sitting on its own rear wheels and tried to bounce the bumper while watching what all was going on underneath. The springs actually appeared to move quite freely, shackles swung no problem. My suspect is (as many of you have said) the shocks. They’re not frozen, but the car basically sits with them bottomed out. Then I can lift the car to full shock-extension, and it stays there. Then I can push it back down again (clunk!). Super weird. It’s like they’re not only shot, but also maybe don’t have enough travel?? So for a cheap place to start, I think that’s where I’ll begin.

Any tips on measuring/buying shocks for a setup I don’t know anything about?

It’ll certainly need springs someday soon, and definitely a lot of the adjustments you recommended seem called for now that I’ve crawled around under it. The rear seems tilted too far forward to me which would wear out my u-Joints and might explain my vibration over 60mph, eh?

Thanks as always for your help


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Oh also, that “lump of nonsense” at the rear shackle was just old grease. Stuck a screwdriver in it, knocked it all away, and now it looks more like a rear shackle.


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And also also, if I’m going to find something used, any other makes/models/years might work that you know of? I’m thinking the 46-48 Chevs were all pretty much the same, but is that consistent amongst sub models? (In other words, would 48 fleetmaster springs work on mine?)

For now I’ll just try to do some shopping and see what’s out there.


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Problem is going with a used spring you may have the same problem you have now.

As you stated the shocks are bottoming out start there.

 

That driver side spring behind the axle has a suspicious lump in the wrapping. Wondering if the spring is buckled or broken under there.

 

Sounds like some progress!

Personally I'd disconnect the shocks and jump on the rear bumper to test out the spring.

If the spring is staying, fine, if going, get a replacement.

Then set that up for position fore / aft and ride height. You can then address the shocks as the final phase. Inclination change would require a top mount replacement, a bottom mount replacement will be necessary regardless, purchase shock length to suit.

That makes it sound easy! How's your welding skills?

Chris

 

Yeah that’s true.

At least I’ll take the shocks off and see how the springs hold up. I’m a little afraid the bottomed-out shocks are bearing a significant portion of the weight of the rear end. Only one way to find out... but if sufficient, then looks like some cheap shocks will run me about $30 from oreilley. That should get us to a few cruise ins before the winter months, and maybe by next year I’ll be able to do a proper rear end job.



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Ha yeah quit making it sound easy. I’m a bit of a sucker...

Meh, decent. I’ve got the patience and the concepts, and some practice (made a real nice MC bracket for the 54 I was proud of, had it checked by a professional welder friend of mine who said “nice work”). I lack in the equipment and knowledge department, with a nice but simple gasless Hobart machine (flux core only) and don’t really know how to set it up to nail it the first time. But I’ve also got help. And you guys to tell me if it’s not up to snuff . I think we’ll manage


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Yea. Wrapping needs removing to find out, should be an easy job when under there removing the shocks!

If, and that's a big if imo, the now unwrapped and tested springs check out to be ok and the plan is to get some cheap shocks to tide over for a short while, measure the length required between the existing shock mounts with the car weight on the suspension. That'll be the ride height required for your new, temporary shocks.

I must admit I never actually drove mine with the tired springs. I was thousands of miles away, buying over the internet! But my buddy test drove it for me and said the rear wallowed like a pig with any amount of power applied. But I could see from the pics it sat nicely! I'd acquired the replacement springs and assorted gubbins to fit them and they were shipped to me with the car. On arrival I didn't get to drive it either as it wouldn't start and the steering wheel fell off when I first got in! But that's another story! First drive occurred a few weeks later once the assorted issues and the rear springs had been resolved.

Chris


Chris

 

If it's any help I've just measured my wheels in the fenders. Axle centerline to fender lip at 12 o'clock is 12.75" As regards for / aft I have 13.25" at the front and 12.75" at the rear - I knew I'd overdone it slightly but I'm happy as it looks 'right' in my eyes! I'm not about to move it forwards 1/4"!!

Car isn't a custom, it has some (front down) rake. Much lower at the front and I'll be having trailing edges of the fenders causing problems with speedhumps.

Hope this helps.

Chris

 

Those looks like Monroe 500 /Magnum shocks that were popular in the 70's but are way too stiff for a smooth ride on anything that doesn't pack a lot of weight. they work great on a 3/4 ton pickup or full size van or 60's 70's Caddy but are far too stiff for that car and probably not in good shape to begin with.
I'd replace those with a set of gas shocks appropriate for the weight of the back end of the car.

I'd go along with making sure all of the leaves in the springs are good and reworking the spring pack for a smoother ride. Taking them apart and cleaning them up and smoothing the ends so they slid over the spring they ride against smoothly is standard procedure.
The ride height should come down to stock height and the axle should center in the wheel well if you use something like this. https://www.classicparts.com/1947-54-Weld-On-Rear-Axle-Seats/productinfo/93-317/ Those are for trucks but I am pretty sure that they will work on a car equally well.
You can drill new holes in the pads about 1=1/2 or 1-3/4 in front of the holes that are centered on the axle to move the axle back with the pads you have but it won't get the ride height back down.

 

Looking at it again you have enough threads on the U bolts that you can get away with making some lowering blocks that are 1 to 1-1/4 inch thick that you can also put offset holes in to move the axle back the right amount. It may take some cutting or grinding to get the width to 1-3/4 wide.
you would drill a hole in it to fit over the spring bolt and one 1-1/2 from it that you can tap and screw a short bolt or stud in to set the perch down on.
It's also going to take a longer driveshaft to get the job done.

 

New leaf springs made a huge difference on my '59 Ford, I still had the wheel hop but the ride was vastly improved. Traction bars took care of the wheel hop on the 1-2 shift. Unhook the shocks at the bottom and see how it rides, be careful as they may have tension on them seeing how short they are. Look around for a higher place on the frame to mount the top. We used to run angle iron or c-channel steel high up on the chassis, weld it in place. Pre-drill holes for the shock studs. A longer shock and less of an angle will help a lot.

 

This is all very helpful guys. Sorry, I’m still working on my masters and have 3 small kids at home, so the hot rod only gets part time attention. Haven’t touched it since Tuesday. I’m hoping to find some time this weekend to mess with it. I’ll keep you posted.

Thanks so very much for the input.


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Well here’s progress! Took the shocks off, that baby bounced up and down like she hadn’t in years. Drove it to work today like that and WAY smoother ride. Some cheap(ish) shocks should tide me over til I can do the rearend right.

Now onto other issues. Like: getting the car started so I can go home from work lol


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Make sure that whatever shocks you choose have enough travel that they do not bottom out during even the worst suspension upset.

 

I’m at 9 3/4 between brackets at rest. Gonna have to do some focused looking to find something that short. How much compression you think I should figure? 2 inches?


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When you go over speed bumps or other things that hit both sides at the same time try to go across them one tire at a time, at an angle.. The same with turning onto or off of a hill, go diagonally one tire at a time so the car doesn't drag or bounce..

 

This might help - Monroe shock spec's:

https://www.google.com/url?sa=t&sou...FjAKegQIChAB&usg=AOvVaw2iIAeE3YvEW_wfxeF8WrWu

See if you can download this .pdf to your device.

 

I have the C.E. leaf spring kit. A '68 Camaro rear with 3" lowering blocks. The ride is pretty nice. It could be a little softer but, overall I like it.

 

If your rear axle has bump stops, try and find a pair of shocks that will allow the axle to hit them. If you don't have bump stops, I suggest you put a set in.

 

More like 4".

It might be necessary to make new lower shock mounts.

I would. I'd get the lower bolt down about 4" and forward 2" from where it is now.

 

Here's something to try.

Put the rear axle on jack stands, with those shocks on trace a Sharpie line around the stone sheild, where it ends, on a shock body.

Take that shock out, full compress it, and trace that line again.

I think you will quickly see how little shock travel you have, and that your problem is that your shocks are bottoming out.

Those are already short shocks.

 

This ^^^^ , but also drill a corresponding hole the spring plate underneath so the U bolts stay perpendicular to the spring plate

The other thing that hasn't been mentioned. Is the driveshaft bottoming out in the back of the transmission? Altering the wheelbase rearward would also fix this.

Apart from the bushings in the leaf springs, The springs themselves do not wear out [they just lose their set or ride height]
If it has stock springs it should have the stock comfort. If not ,then something else is the problem [shocks, binding, bottoming out etc]

The shocks should be moved outwards closer to the wheel or the valving will be too soft [except when both wheels go up/down together]

 

Hey there,

I’m dusting off this thread and renaming it. Once I got the motor running properly, the pinion pitches up and the u-joint whacks that crossmember when under a hard pull. Makes an awful racket. Looking closer, the bottom plates that the U-bolts hang onto are strangely thin and bending around the axle, which I don’t like. So now is the time to take it all apart. No cruise-ins for us this year. Better luck in the spring.

Also I’m gonna rename the post if I can cuz it’s not so much about comfort anymore, and I want to have all this valuable info in one place for my reference.

Plus my wife gets tickled to death when I try to explain to her that “when I give it a lot of gas, my rear end squats too much and starts making an awful noise.” I’m being serious. She’s not. Just what I need most days.


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