The Stovebolt Site Forums The Shop Area Driveline Front axle.

Hey guys I want to put the 6 degree shims under my front axle on my 51 but when I started to do it I found out the U bolts that are there are too short. I have looked all around and cant find any longer that will work. Any suggestions?

A local spring shop might be able to make them. (not a common shop, even in large cities)

Eaton Detroit Springs might have/make them.
https://www.eatondetroitspring.com/

ESPO Springs might have/make them.
http://www.springsnthings.com/

Six degrees is a lot, did you make some big changes that require that much?

Ed

Can you give us a little more info? Has somebody told you to use 6 degrees? Manual steering? Wide tires or not? Stock U bolts? Old springs or new? Modified springs or stock?
The reason I ask is with 6 degrees with good stock springs I believe you might be flirting with some jacking effect considerations.
Jon

6 degrees is needed when converting to power steering with a smallblock swap. I believe the reason is due to the considerably lighter engine weight not compressing the leaf springs as much as the heavier stock inline six cylinder. Could be that it changes the geometry.
Without the extra castor, there is no return-to-straight-ahead action when coming out of a turn.
Any time you remove the U-bolts, it is advisable to replace them with new ones. I had some longer ones made by a local spring shop. I brought my old ones to them and asked them to make some new ones 1/2 inch longer. They made them while I waited. About 15 minutes.
Carl

I have small lock v8 but all springs and hardware is stock. I have 15 inch tires. I did put power steering on it and it road walks real bad when I hit a bump. I just read that the fix for this was shims. Most people that has this problem state that they put 6 degree shims to fix it. The truck is factory suspension.

Ok, that makes good sense. Where in Texas are you? Truett-Worrall Company off of Harry Hines on Hinton St. (north of the Parkland Complex) will make those U-Bolts for you.
Jon

Good info on the shims. I don't have power steering but have quite extensive mod's to the OEM steering assembly to shoe horn an SBC in. I retained the existing shims that was on it and for the most part the steering returns to straight except when I go full turn to the stop, then I have to manually start turning the steering wheel until it hits a sweet spot and it returns on it's own.
I'll add 6 degree shims to my shopping list.

Dave

One thing to watch for when using such thick shims is the length of the center pin head in the leaf spring. If the head of the center pin does not reach all the way through the shim, you will have no way of locating the axle correctly. As you know, the axle has a hole where the spring pin goes.

Excellent point Joe, and even if you get it right the axle won't have any way of staying put if you hit a pothole, curb, large rock, whatever. Which I think is why the shop manual says it is inadvisable to use shims to correct more than 2 degrees...
Jon

I get what your saying Joe. I know about the pin. If it too short then is there another way to keep the truck from wandering when I hit a rough spot in the road.

If your shim has a hole in the bottom, you clamp the spring down using large C clamps, remove the original center pin (you'll need to file or grind the top of it down and you may have to hold the old pin with vise grips), install the shim oriented the right way on the bottom, slip a new and longer center pin in and tighten it using some sort of thread locking paste. You'll need to trim it at the top for the frame bumper to fit. Leave about 1/16 inch above the nut and pound it down with a heavy hammer. You don't want there to be any chance it might unscrew. Then the whole she-bang sits on your axle and the pin fits in the hole and you're ready to go. You might need longer U bolts or you might not. 6 degrees is on the high side. If your shim doesn't have a hole in the bottom, drill one the size of your center pin's bolt section. If your shim has a U shape cut in the bottom, send it back for a refund and get one with the right size hole in it. Sometimes the shims will come with new center pins.

Please don't mickey mouse anything to do with that spring pin or the U bolts. If you've ever seen a situation where an axle became loose, unconnected or shifted on the spring, you know how dire the consequences are, how fast control is lost and how everything instantly goes to poop when the driver hits the brakes and they almost always do.
Jon

"it road walks real bad when I hit a bump"

That sounds a lot more like bump steer than improper caster. Is your drag link still parallel to the ground? What type of power steering system are you using, and is the steering geometry correct? It sounds like the excessive caster is a "band-aid" fix of a more serious, possibly dangerous problem.
Jerry

The drag link is parallel to the ground. It's not bad driving. I put a CPP power steering kit and it works well. It will return most the way back to center after you make a turn. It steers good but it just feels like an old worn out steering box with a little play in it. The steering shaft has 2 unions in it and they have a small amount of play. I just heard that the shims would tighten up the steering and keep it from road w as long a bit. Thanks for the help guys. I have restored cars all my life but never a truck as old as this.

That tells me you (for whatever reason) do not have enough caster angle. Not yet anyway. I'm still not convinced 6 degrees is right, but it might be. It sounds like too much to me. Having said this I'm assuming you have checked the toe-in setting. You need to do this, but really what you're describing sounds more like caster. In a minute I will tell you how to solve this whole caster riddle if you want to do it. First, if you have too much caster, your truck will be hard to steer. You're having to lift your truck up every time you turn it. If you have too little to no caster, your truck will steer easy as pie but it will wander around all over the place and this can definitely cause it to feel like the steering gear is loose. With not enough caster or no caster weight and gravity force your pivot points downward perpendicular to the ground and there is no reason for your front wheels to want to center themselves. The faster you go the worse this gets, by the way.

In high school a friend bought a truck with this same problem. You could steer it with one finger but it would roam around everywhere. Scary to drive. He didn't have the money to have somebody look at his front end, so here is how we figured out what angle he needed and you can do the same thing: Starting with no caster at all, we took small bolts cut off to a length of about 1/4 inch (behind the head). We made 4 of these for each try starting with some which were larger than the shims which had been in the front to begin with. We would loosen the U Bolts, jack the truck up so the axle fell away from the spring and poke those little cut-off bolts in at the back (2 on each side about a quarter inch in from the edge of the spring). Then we'd tighten the U Bolts and drive carefully down a smooth road for a mile or so. Then we'd try with slightly larger diameter bolts making certain the center pin was still catching and we kept repeating this until the truck became too hard to steer. We figured this was our upper limit. Then we backed off until we found a thickness that would cause the truck to drive straight but not cause it to be too hard to steer. It took a while to find that point but you'll recognize it when you get there. Then we knew the shims had to be the same thickness as those bolts in the back tapering to nearly nothing in the front and he got the FFA teacher to help him figure out how to make some.

Good luck!
Jon

"I have restored cars all my life but never a truck as old as this."

Herbert,

When my now-restored to original '36 Chevy pickup was a daily driver rat rod with a sbc engine and B&M "Hydrostick" trans back in the 1960s it had the same stock front suspension as it has today without any steering problems. Perhaps the problem is something other than caster. Is the toe in within spec?

I believe I am right here, if you lower the rear of the truck, the caster will increase. Raise the rear and caster decreases.

What is the condition of your king pins, wheel bearings, tie rod ends, spring eye pins? Many of these have adjustment procedures to tighten them up. How loose are your steering u-joints? They should not be loose at all.
Carl

So you are saying I still probably need shims just maybe not 6 degree. And I need to put them where its tilting the axle down in the back side. What i am saying is the front straight axle toward the back of the truck needs to go down.

Thanks so much guys.

Here is a fairly good and interesting article about front end geometry: https://www.glenngoodspeed.com/volvo/caster.htm

If you stand at the side of your truck (driver's side) and study your front axle without the wheel mounted, the axle should lean backwards. This is to say your pivot points (top and bottom of the steering knuckle) must lean backward. It won't be a lot, but you can see and measure the angle. How much that angle should be depends on several factors. As mentioned above, the condition of your kingpins, bushings, wheel bearings, etc is important. Tie rod ends and your drag link connections are also important. I would think you probably already checked these but if not, please do.

Once you have a good understanding of geometry, you can set up a front end that will run straight and true with very little bump steer, wandering, etc and one which steers pretty easily. One item these trucks needed was an anti-sway bar.

Yes, 6 degrees might be too much, but at this point there are too many variables to say. That's why I told you how a friend and I solved his problem. We had no idea what degree of camber we needed, but once we found an angle that kept it going straight and didn't require Bluto in there trying to steer it, we were good to go.

Good luck,
Jon

Herbert,

My shims go into the backside of the axle not the front. It leveled my axle so that it was parallel to the ground. I used them due to the 4” dropped axle and 3” lowering blocks in the rear.

Thick part of shim goes towards the back of the front axle.

Well I have checked everything I can see. My axle does have a slight lean back on it. Everything looks like it supposed too. I am starting to think that I am just not use to this type of front end. I think it might be the leaf spring suspension in the front. It makes the truck ride real stiff in the front and it bounces a little. I am going to try to let a bit of air out of the front tires to see if that will help. It's just really very stiff in the front and I really think I am not accustom to that ride yet. The last time I drove it last sunday I drove about 60 miles and I remember saying that it seems like it's getting better but maybe it's me getting more use to the stiff ride. Thanks again guys.

Shouldn’t the axle be parallel to the ground?

First of all, Hebert...if you have a sbc engine, your stock front springs are going to be too firm. Somebody else already mentioned this. You have springs designed to carry an engine weighing somewhere around 650 pounds but your sbc engine weighs somewhere around 500 or a bit less if you have aluminum manifold and heads, so you need slightly weaker springs or a 150 pound friend you can tie to the front of your truck. You need help from somebody who knows what they're doing, too. A person before you made changes to the fundamental design of the truck without considering the downstream effect. This isn't to say the original 6 and the original springs rode like a dream but their springs were matched to the weight. I don't know where you are in Texas, but you might see about consulting with a spring shop. I've seen people remove leaves from these springs to make them ride softer, but most of those people have no idea what they're doing and honestly anything that might in any way cause risk of a broken main leaf is something you never want to do. In your case I would look for some educated help. Jerry might be a good place to start. He has a great knowledge of this stuff and can help you dodge the pitfalls.

Ndkid, from what you've written your truck has been lowered in the front and the back and it sounds like the back might sit slightly higher than the front. I'm sorry but with I can't answer with any clarity. Your axle has been modified and I don't know what was done, by whom, if they built a fixed caster angle into it (which I never would have done), what camber angle they built into it, what kingpin inclination degree they used...anything. Sorry but I feel like a doctor when a patient calls up and says "doc, I feel bad. What do I have?" I'd say if yours drives right and doesn't wander or scrub the tire treads off too fast, leave it and enjoy it.

Let me try to show an example of the caster angle:
http://i1154.photobucket.com/albums/p535/JonGoodman/Caster%20at%200.jpg The floor is pretty well level. If I could get in there to take a better picture, you could see the needle is just a hair from zero
http://i1154.photobucket.com/albums/p535/JonGoodman/Caster%20at%203%20degrees.jpg And with this little gizmo held right up against the kingpin/steering knuckle you can see it is 3 degrees positive. I don't hold it up against the axle. That doesn't tell me squat because I don't know what it bears to the kingpin line. Three degrees is what I want for my starting point. I know at this spot it will run straight and if it steers a little hard, I can go lower.

And I can tell you what the factory wanted your truck to have when they built it:
Caster angle---1.75 degrees positive plus or minus .5 degrees
Camber angle---1 degree plus or minus .5 degrees
Kingpin Inclination---7°10' plus or minus 1°
Toe-out on turns---outside wheel 20 degrees, inside wheel 23 plus or minus 2 degrees.

Them's the numbers. If your springs are good and your tires are the same height, your wheel bearings and kingpins are good, your tie rod ends and connectors are good (not egg shaped or loose), your drag link is right and steering box adjusted correctly and you have the front end set up with these specs, it will drive pretty much like a new one. And that isn't a bad thing. You can make the front wheels track better by adding a degree to the caster (total of 3 degrees or less), but it will not steer as easily. Study the way the angles work, see why caster works in the first place and you'll see why larger caster angles increase steering effort. Bikes and some motorcycles have (by comparison) extreme caster angles but they have very little weight to speak of over the front tire.
Jon

The front end is all factory stock except for the power steering I put in the truck. This truck is never been lowered or modified in any way except for the power steering kit I put on the truck. It has a small block olds 350 which is probably a bit heavier than a sbc's. I think I will talk to a shop about front leafs.

leads. Thing is new in the front so all is good and tight. I did just find out that I have about a half inch of toe end.

Jon,

I had my axle bent by sids dropped axle. He told me 2 1/2 degree shims we’re required since front is 1” lower than the back. He stated the shims would keep the axle at the stock angle to the ground.

I was only asking if the axle for his truck should be parallel to the ground like it was stock. I wasn’t sure if having front/ rear of front axle lower would upset the geometry that was intended.

After reading your information above, as long as king pins are at the correct angle, the axle doesn’t matter? (Obviously other geometry as well)

I am asking to gain knowledge. By no means am I giving advice.

Chris

I dont want to lower the front because I like the stock ride height. Is there a way to soften the ride and still keep the truck safe.

Hi Chris,
Sid knows exactly what he is doing, so no worries there. If front is lower than back, your caster angle will be reduced, so if he has you using 2.5 degree shims, you're very close to stock or certainly in the range. As I've said many times I prefer a little more caster to force the wheels to return to straight out of turns and to make them stay between the fence posts while I'm driving. If your back is lower than your front, your caster angle will be increased (obviously, but I find a whole lot of people will put larger tires on the rear and never think about what it does to the steering). If you put something very heavy in the very back part of your bed and it squashes the springs down, you may find your truck steers really easily (from the weight shift) and stays straight (from the caster increase) but of course this isn't a safe steering situation.

In the 80s a friend put some huge tires on the rear of his truck and some on the front that were maybe 24~25 inches in diameter. He told me one day "I like the look and the thing has never steered easier but it wanders so much I'm scared to death to drive it." He had created a generous degree of negative caster with the changes. Something else not everyone understands is positive caster will additionally reduce the amount of negative camber increase while you're turning. Which is really what you want happening up there.

The old truck axle if you look at it has a ridge on top where it was cast and so does the bottom side. And then where the springs mount it is nice and flat. So there is no flat side on which to get a level measurement anywhere but where the springs mount. In addition to this, the top strength "lip" (angled out ridge) and the bottom one are not equal, so using a level or a t-square will give you wacky results. So yes, definitely to answer your question, the king pin angle (which determines your caster) is all we need to care about. The stock axle wasn't really parallel to the ground (if you look front to rear). If you had somebody to mill the bottom of it so that it was perfectly perpendicular to the spring mount area, then it still wouldn't be parallel, either. Because once we put a shim in there it would tilt backwards by the thickest part of the shim, giving us the positive caster we need.

Hebert...Can you soften the springs and keep the stock height? Yes, I think so but you need to talk to a really good spring guy. You're going to need to have some springs made for the sbc engine's weight which preserve the stock height...and maybe they're already out there. You could use Google and search. Or possibly some spring guy would know how to determine if you could safely modify the stock springs. I don't know diddly about making springs, but I agree with you on the stock height. That is one of the things I like about the look of these trucks. I'll bet Jerry knows about springs. Ask him and see...
Jon

Thanks Jon! I appreciate you explaining that to me.

Chris

This topic and post is very helpful to me. So I have one question that I don't think has been mentioned. I have a 49-3100 "stock" suspension. What is the "best" shocks. And if there is a make and part number I would appreciate it.

To help with ride only, nothing to do with steering, you can remove a few leaves from the spring pack. Once done, the hauling weight limit will be compromised so keep that in mind. Start at the top, the longest leaf, this is the main one, the second leaf is the main leaf support, both these must be in good condition and stay in place. Now you can remove every other leaf verifying that each leaf is not worn or damaged. I don't know how many you are working with, so you may want to start three down instead of two and see how it rides. Add Teflon liner between each leaf when assembling, ( https://www.speedwaymotors.com/Leaf-Spring-Liner-with-Lip-1-3-4-Inch,2079.html ) , this will really help. Replace the center bolts and use clamps to hold everything together while working on the springs. You might have to bend the spring clamps to account for missing leaves, and you will have to open them up the get the spring pack apart. It's not super hard work, and it will give you a chance to inspect the springs. To keep the same ride hight, add a spacer the same thickness as the leaves you remove to the bottom of the stack.

Adding the liner to all four corner will help so once the front is done, move to the back and add some more.

Joe