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Old 12-08-2017, 10:20 AM
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Straight axle assistance

I have some questions, someone recommended this as the best place to ask Ill try and cover whats going on and what Ive done

Vehicle is a 67 Falcon

Bought this https://www.speedwaymotors.com/Gasse...Hub,35554.html straight axle kit.

I didnt like the main spring cause its so short, looked like it was better suited for a trailer so I had 2 new main leaves made up 8 inches longer. I will use the rest of the spring pack that the kit provided.

Im guessing Im gonna improve overall ride quality with a longer spring as well.

Ive mounted the springs, shackle end is welded to 1/4 plate and is welded to the underside of my torque box, fixed end is welded to a 5 inch drop that is welded to the outer rail ends. ( zero chance of anything moving )

The installation instructions say to mount the axle under the springs, I dont want the front end sticking stupid high up in the air so Ive flipped my perches and have my axle just sitting on top of the springs.

Im at the point now however that I need to stop.

Evidently I dont know enough about setting up caster and I need a lesson.

Car has no engine in it, not ready yet to put that back in.

Ive read that how the car sits and drivetrain can have a major affect on caster and Im slowly understanding.

Ive read that I need to have all 4 wheels and tires on the ground and an engine in its place before I set the caster.

If thats the case than it sounds like I cant complete this part of the project at this point and Im hoping there a way around that.

Never mind the missing engine but how would one go about setting the front wheels on the ground with an axle that sits on top of the springs and of course isnt welded into the perches?

Im going for as decent of a ride as I can get from this straight axle, not looking to just throw something together and hope for the best

Im gonna throw a couple of pictures just to say I did, maybe they will help.

Thanks for any help with this
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Last edited by Oilyrascal; 12-08-2017 at 10:32 AM.
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Old 12-08-2017, 10:36 AM
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You should have u=bolts and perches in the kit,, Just set the axle perches on the spring and the axle on the perches. Use the u-bolts you have as when they are tight they will clamp the axle in place well enough to roll the car around. Been there done that..

Sam
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Old 12-08-2017, 10:44 AM
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Quote:
Originally Posted by OneMoreTime View Post
You should have u=bolts and perches in the kit,, Just set the axle perches on the spring and the axle on the perches. Use the u-bolts you have as when they are tight they will clamp the axle in place well enough to roll the car around. Been there done that..

Sam
The U-bolts hold the perch to the spring, not the axle to the perch

It may be that I need to get a second set of perches to mount on top of the tube and then longer U-bolts

Last edited by Oilyrascal; 12-08-2017 at 10:53 AM.
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Old 12-08-2017, 11:03 AM
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Quote:
Originally Posted by Oilyrascal View Post
The U-bolts hold the perch to the spring, not the axle to the perch

It may be that I need to get a second set of perches to mount on top of the tube and then longer U-bolts
Yup I have had to do things like that.. Off to the parts store we go..

That should be a 2 inch axle tube so tractor supply may have the ubolts and perches you need..

Sam
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Old 12-08-2017, 11:04 AM
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Straight axle.

Greetings, I have used this same kit and also did not like the height with the axle under the springs. My solution was just use the axle mount brackets on top of the spring, use longer U bolts and I made a under spring plate which had holes drilled for the U bolts to go through. I used this modification on both a straight axle and a 4 inch drop tube axle.

Remember you have to drill a centering hole on the bottom plate for the centering bolt that goes through the center of the leaf springs. This mounting design is actually stronger and safer than the original mounting design. Should a axle perch mount break the axle is still locked in position and can't move anywhere.

For caster, with the frame level, I tilt the top of the axle back 7 to 10 degrees and weld it to the spring perch mounts brackets. Some say that 10 degrees is a bit much, however when driving it helps the vehicle drive straight and allows the wheels to easily come back to center after making a turn. Also remember if your vehicle has a nose down rake, depending on frame rake, 10 degree caster can be 5 to 7 degree or less. Take this in account when setting up your caster angle.

This design does not have to use exact Ackerman design steering arms geometry (although recommended) and they still drive very good.

Some high speed vehicles using straight axle designs use much higher caster angles which help keep the car straight at high speed, however extreme caster angles are not desirable for a street vehicle where taking corners is normal driving. Therefore 7-10 degrees work well on a street car.

And yes, I am old and actually worked on many factory straight axle vehicles.

Last edited by BadWally; 12-08-2017 at 11:23 AM.
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Old 12-08-2017, 11:23 AM
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Quote:
Originally Posted by BadWally View Post
Greetings, I have used this same kit and also did not like the height with the axle under the springs. My solution was just use the axle mount brackets on top of the spring, use longer U bolts and I made a under spring plate which had holes drilled for the U bolts to go through. I used this modification on both a straight axle and a 4 inch drop tube axle.

Remember you have to drill a centering hole on the bottom plate for the centering bolt that goes through the center of the leaf springs. This mounting design is actually stronger and safer than the original mounting design. Should a axle perch mount break the axle is still locked in position and can't move anywhere.

For caster, with the frame level, I tilt the top of the axle back 7 to 10 degrees and weld it to the spring perch mounts brackets. Some say that 10 degrees is a bit much, however when driving it helps the vehicle drive straight and allows the wheels to easily come back to center after making a turn. Also remember if your vehicle has a nose down rake, depending on frame rake, 10 degree caster can be 5 to 7 degree or less. Take this in account when setting up your caster angle.

This design does not have to use Ackerman design steering arms geometry and they still drive very good.

Some high speed vehicles using straight axle designs use much higher caster angles which help keep the car straight at high speed, however extreme caster angles are not desirable for a street vehicle where taking corners is normal driving. Therefore 7-10 degrees work well on a street car.

And yes, I am old and actually worked on many factory straight axle vehicles.
So what did you put between the axle and the spring?
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Old 12-08-2017, 11:24 AM
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Youve got a plate on the bottom under the spring, youve got the perch on top of the axle, whats in between the spring and axle?
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Old 12-08-2017, 11:39 AM
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Quote:
Originally Posted by Oilyrascal View Post
Youve got a plate on the bottom under the spring, youve got the perch on top of the axle, whats in between the spring and axle?
The perch goes between the spring and the axle..

Sam
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Old 12-08-2017, 11:42 AM
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straight axle.

You have the perch that is a saddle for the axle like in your photo. Make sure the axle is centered side to side. with the frame level, tilt the top king pin hole back 7 to 10 degrees and weld the perch saddles to the axle. Then use longer U bolts (easily obtained from a trailer supply store), the U bolts have to be long enough to extend down past the bottom of the spring about 2 inches. make a 3/16 or 1/4 inch thick rectangle plate with four holes for the U bolts to pass through and a centering hole for the leaf spring centering bolt. Fasten everything down. If the U bolts extend to far past the U bolt nuts, Just cut off to the proper length leaving at least 1/4 inch extending through the nut for safety.

I think the confusion is you do not use the Square "U" bolts included in the kit. Go buy U bolts that go over the top of the round tube axle and extend past the spring. Hope this Helps.

Last edited by BadWally; 12-08-2017 at 11:55 AM.
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Old 12-08-2017, 12:09 PM
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straight axle

I hope I have not confused this, I am old and do not know how to post photo's.

One thing that I did on both the speedway kits I installed, I took the perches(the saddle brackets where the axle will be welded) they are wide because the original design has those square U bolds going through them. I cut my brackets lengthwise and re-welded them so the bracket is only as wide and the leaf spring. Then the new U bolts just go over the axle tube, on both side of the leaf spring and just through the bottom plate.

Just look at the leaf spring rear suspension on any truck and you get the idea. that design uses over the axle u bolt and it secures through a bottom plate. the axle perch is also weld to the axle.

You are doing the same design only on a front axle.

Both axles I installed this way drove great and one now has about 12,000 miles with no issues.
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Old 12-08-2017, 12:47 PM
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Quote:
Originally Posted by BadWally View Post
I hope I have not confused this, I am old and do not know how to post photo's.

One thing that I did on both the speedway kits I installed, I took the perches(the saddle brackets where the axle will be welded) they are wide because the original design has those square U bolds going through them. I cut my brackets lengthwise and re-welded them so the bracket is only as wide and the leaf spring. Then the new U bolts just go over the axle tube, on both side of the leaf spring and just through the bottom plate.

Just look at the leaf spring rear suspension on any truck and you get the idea. that design uses over the axle u bolt and it secures through a bottom plate. the axle perch is also weld to the axle.

You are doing the same design only on a front axle.

Both axles I installed this way drove great and one now has about 12,000 miles with no issues.
I do appreciate your calrification, its clear to me now, I am able to do any job but I lack fabrication experience so the simplest of ideas escape me.

If you would watch this thread, Im gonna at this point get myself set-up with the parts, re-read the posts and then im sure Ill have more questions.

Thanks again
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Old 12-08-2017, 04:02 PM
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Quote:
Originally Posted by BadWally View Post
I hope I have not confused this, I am old and do not know how to post photo's.

One thing that I did on both the speedway kits I installed, I took the perches(the saddle brackets where the axle will be welded) they are wide because the original design has those square U bolds going through them. I cut my brackets lengthwise and re-welded them so the bracket is only as wide and the leaf spring. Then the new U bolts just go over the axle tube, on both side of the leaf spring and just through the bottom plate.

Just look at the leaf spring rear suspension on any truck and you get the idea. that design uses over the axle u bolt and it secures through a bottom plate. the axle perch is also weld to the axle.

You are doing the same design only on a front axle.

Both axles I installed this way drove great and one now has about 12,000 miles with no issues.
Curious to know which end you put your shackles on? I see some very good arguments both ways online.

If it were such a pain in the rear I would cut mine loose and put the shackle at the front ( cause I like the facts Ive read ) but at this point Im gonna leave them as is with shackle in the rear.

Also what cars did you say you had done and drive? Did you use existing frame rails or box something in? What sort of mods did you have to do to get everything to sit right?

Pictures would be nice if possible

Last edited by Oilyrascal; 12-08-2017 at 04:27 PM.
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Old 12-08-2017, 06:03 PM
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Straight axle

Greetings, the 4" drop axle was in a 1940 Dodge truck which I used the Speedway springs. It had a slight rake and I used a 10 degree caster angle with a cross steer set up. It drove really well. With the rake, when the vehicle was on the tires the caster angle came to 5 degrees.

The other straight axle was in the front of a 47 Willy's CJ2. I used new replacement stock jeep leaf springs. It had a narrowed ford Rear end with a 327 & turbo 350 drivetrain. It drives great and sits like a stock jeep. Most people never know it's only 2 wheel drive.

When I use the cross steer, especially with a short wheel base light vehicle, there is no need for power steering. A short wheel base vehicle and quick steering is a recipe for disaster, it makes the vehicle twitchy at highway speeds. I use early a Jeep CJ5 manual box. The Jeep manual box is much like a Saginaw 525, they may be the same. It is stout for a full size vehicle and has a low ratio. It allows for a very good steering feel and makes parking a one arm job with a 13 to 15 inch steering wheel.

Since you are building a gasser type chassis, your vehicle stance is elevated and a slow steering box will give you a good feel when cornering at highway
speed.

Just something to think about.

I also always put the shackle on the front of the spring. The reason for this is when braking the vehicle does not dive and maintains good steering control. . It allows the spring section from the axle centerline to the rear spring eye to act a solid arm, very important when braking in a corner/turn and maintaining control. Ford used a rear shackle design in straight axle 4x4 trucks for years, but it was in the 3/4 ton and one ton trucks which had very stout springs. It just makes sense to use the shackle in the front for good handling on a street car. .

Last edited by BadWally; 12-08-2017 at 06:15 PM.
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Old 12-09-2017, 03:52 AM
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Quote:
Originally Posted by BadWally View Post
Greetings, the 4" drop axle was in a 1940 Dodge truck which I used the Speedway springs. It had a slight rake and I used a 10 degree caster angle with a cross steer set up. It drove really well. With the rake, when the vehicle was on the tires the caster angle came to 5 degrees.

The other straight axle was in the front of a 47 Willy's CJ2. I used new replacement stock jeep leaf springs. It had a narrowed ford Rear end with a 327 & turbo 350 drivetrain. It drives great and sits like a stock jeep. Most people never know it's only 2 wheel drive.

When I use the cross steer, especially with a short wheel base light vehicle, there is no need for power steering. A short wheel base vehicle and quick steering is a recipe for disaster, it makes the vehicle twitchy at highway speeds. I use early a Jeep CJ5 manual box. The Jeep manual box is much like a Saginaw 525, they may be the same. It is stout for a full size vehicle and has a low ratio. It allows for a very good steering feel and makes parking a one arm job with a 13 to 15 inch steering wheel.

Since you are building a gasser type chassis, your vehicle stance is elevated and a slow steering box will give you a good feel when cornering at highway
speed.

Just something to think about.

I also always put the shackle on the front of the spring. The reason for this is when braking the vehicle does not dive and maintains good steering control. . It allows the spring section from the axle centerline to the rear spring eye to act a solid arm, very important when braking in a corner/turn and maintaining control. Ford used a rear shackle design in straight axle 4x4 trucks for years, but it was in the 3/4 ton and one ton trucks which had very stout springs. It just makes sense to use the shackle in the front for good handling on a street car. .
Understood Im using for now the stock manual steering box that is mounted on the drivers rail just outside the firewall, ( no different than a Mustang ) I think there are a few options for steering, I need and will read up on some of them.

Do you know what my options are? Ive heard of the crossover steering. Not perfectly clear of what that is but I think that is what I may need to use with this axle that I have?

I havent got that far with this yet to see how all this is gonna work.

Evidently I may need to come up with a dropped pitman arm as well? I dont know how much of a drop yet and what my options are gonna be when I do get there.

Anything you can say that might enlighten me on some of this stuff would be appreciated.
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Old 12-09-2017, 09:33 AM
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straight axle

Greetings, Cross steering is very simple, it actually reduces "Bump Steer" and is very positive type steering linkage with little play. One issue is if there is limited oil pan clearance and engine location. Speedway has actual diagrams on their website that shows drag link and cross steering designs.

As to the steering box issue, when I use the Jeep CJ5 manual boxes, you have to remember that a jeep box on the jeep frame is mounted in front of the axle and the steering arm goes to the rear. What is nice about the jeep box is that when using it on a hotrod for cross steer, it is now mounted behind the axle, now the steering box arm has to be removed and turn 180 degrees to face forward. The jeep box has 180 degree locator splines that allows for re-clocking of the steering arm on the box to allow the arm to be placed in the correct position. Some other type boxes have a locator spline arrangement that does not allow this.

I do not know which type steering box you have, the manual box for cross steer usually needs to be moved forward of the firewall location inches or farther depanding on the frame and engine location. This requires double "D" steering joints and shaft. . Lots of hotrods use a aftermarket Vega box design, they are OK on a very light vehicle, are small and easily mounted for tight engine compartments, Like a Model A, B(32 Ford) or t bucket open wheel car. I prefer the larger 525 type box when it is out of sight on a fender car. A little overkill and slightly more cost but many miles from now you would be glad you took the time. Safety first.

So, if any of this seems confusing, I suggest you go to some hotrod shows and take pictures and talk to owners about their cross steer design.

It's good that you are educating yourself on suspension and steering, I am confident yours will turn out good and drive nice.

Good luck on your project.

Last edited by BadWally; 12-09-2017 at 09:46 AM.
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