[31fordcoupe]

Hey guys,

I am trying to convert my 31 Ford to a leaf spring set up on the rear. The pictures that I have attached are what I am starting with (and no, I did not fabricate this mess). I have never done this before and have some questions:

1. How many leaf springs should I have? 2? 3? 5? I would like about the same ride height that it is at now.

2. Is it critical where I mount them on the rear part of the frame? I was thinking at the very rear of the frame and going forward to the level part of the frame on each side.

3. Would it be better / easier to go to a coil over set up like that which is pictured on this t-bucket (with the chrome rear end) in conjuction with a set of radius rods?

I will be removing the arms that are currently under this rear end as well as the coil springs obviously.

Any and all suggestions are welcomed. I am going to need a lot of help on this one. If anyone has some diagrams or pictures of what would work on this I would be forever in your debt.

The pictures are at this link. http://www.hotrodders.com/gallery/sh...0&ppuser=73238

They were to large to post on this page.

Thanks again.

Brent

[Frisco]

Here are the pictures for all to see in this thread.

Originally Posted by 31fordcoupe

1. How many leaf springs should I have? 2? 3? 5? I would like about the same ride height that it is at now.

The number of leaves will determine the harshness of the ride as well as the travel up and down. The ride height will be determined by both the number of leaves, the arch of the springs, as well as the actual mounting points.

Originally Posted by 31fordcoupe

2. Is it critical where I mount them on the rear part of the frame? I was thinking at the very rear of the frame and going forward to the level part of the frame on each side.

Looking at the frame, the rear of the frame may need to be extended to have the rear attachment point a greater distance from the centerline of the rear axle. At the present the rear portion of the spring would end up being much shorter than the front portion of the spring if the front was attached to the level part of the frame.

Originally Posted by 31fordcoupe

3. Would it be better / easier to go to a coil over set up like that which is pictured on this t-bucket (with the chrome rear end) in conjuction with a set of radius rods?

Better? That would be more of a personal choice decision. The coil overs will look cleaner but will ride somewhat harsher due to the light weight of the vehicle.

Easier? Depends on your fabricating skill level. Keep in mind that with the coil overs you will need a panhard bar or watts linkage to keep the rear axle located if you use parallel four bar radius rods. If you go with a triangulated four bar setup you will not need the panhard bar. With parallel leaf springs you should consider addding traction bars to reduce spring wrap up on hard acceleration.

COMMENT:

I'd suggest you consider using the existing coil spring set up. Remove the existing trailing arms and fab up some better looking rear radius arms. You will also need to add a panhard bar with the coil spring rear. The ride will be much better than the options you have asked about.

Look at the pictures below. This is a coil spring set up I did back in the '60's for a 'T' roadster pickup.

[31fordcoupe]

Frisco,

Thanks alot for the suggestions and help.

Can I use radius rods and coil over springs like I have pictured in my old T-bucket picture? I think it looks better and will be more at my skill level of installation.

Also, is the panhard bar that you are referring to that bar that parallels the axle in your last picture (runs above the pumpkin)? I believe that just goes across and attaches to the frame correct?

Finally, if I go with a coil over set up with the radius rods, how critical is the angle of the coil over shocks? Is it best that they are perpendicular to the axle? Or can they have a slight angle like is pictured in my T-bucket photo?

And just out of curiousity, what held your springs in place other than the weight of the vehicle on that T roadster pickup? My neighbor and I (both somewhat novices to this) were concerned that if you hit a big enough bump the springs could go flying if they left their perch. I know we are idiots about this but trying to get it right the first time.

Thanks again. You have been a big help already.

Brent

[powerrodsmike]

If I were you, I would follow Frisco's suggestions. you'll have a car that rides fine with minimal modifications to what you have there. Just make sure the frame is sound, check the welds and wall thickness on all of that arrangement.

If it was my car, I'd use a set of four bars, it looks like you could install a set of the ready made ones from one of the places like Speedway motors. Yes the panhard bar is to keep the rear end from moving side to side, and is necessary in most of the options being discussed, a leaf spring setup does not need a panhard bar.

With 4 bars, you could run the coils springs you currently have, or put a crossmember and go to a coilover setup. (I would add a crossmember to connect the 2 ends of your current frame anyway)

The shock absorber is supposed to limit the amount of upward travel you have, and keep the spring under compression so it doesn't fly out when you catch some air going over bumps.

Later, mikey

[31fordcoupe]

Thanks for your input Mikey.

I have one final series of questions (and they're newb questions).

On the radius rods or the panhard bar, what is the best way to attach the chromemoly rod ends to the frame? The clevis ends are pretty straight forward but do you just run a bolt through the chromemoly rod end and attach it to a welded bracket on the frame or what?

Also, I noticed on Frisco's build up, the radius rods were at a relatively extreme angle compared to what I have seen before. Does it matter if the radius rods are on the inside or outside of the frame and is the angle of the radius between the axle and the frame very critical?

Thanks.

Brent

[powerrodsmike]

You can bore a 1 1/8" hole through the frame, then weld a through tube with about a 1 1/8" OD and 5/8 ID so that it penetrates the frame and can be welded from the inside and outside, leave enough sticking out so that the radius rod will clear the frame. (that way your spacer is built in), Then bolt the radius rod up using washers on each side of the rod end that are large enough to cover up the urethane bushing.

I've not seen anyone run radius rods on the inside of the frame, but I suppose you could. I'd be concerned that they'd not be strong enough without the full width installed on the axle...especially with those wide tires you have in the pic...Ladderbars yes, radius rods, hmmm. I see 4 bars on mounted on the inside.

You can buy angled rod ends to get the bolt going straight through the frame. Or put the through tube on an angle to match your rod end..The more severe the angle, the more bushing wear you'll get. I try to keep the angle below 5* if I could.

You can also buy or build build a drop down bracket, to get the mount under the frame, but I don't think you'll need it for what you are doing.

Panhard rod you might need to build a drop down bracket out of rectangular tubing, hang it down from the frame and attach the rod end either by cutting a opening in the side of the tubing so it makes a channel for the rod end and then bolting it through, or do a shorter version of the through tube as described above. Some guys make the frame bracket out of plate, with just a hole for the rod end bolt., the ideal panhard mounting bracket is centered on the axle tube, as far out as you can get it, the bar as long as you can stand it and is level at ride height. The ones that mount on the pinion are ok, but the axle moves a little more laterally as the suspension moves up and down, than the long bar.


You can also just put a tab on the frame, and build a bracket on the axle so the panhard bar sits above the axle, just watch out for things hitting when the suspension moves.

[31fordcoupe]

You rock Mikey. That helped a bunch. I think instead of drilling through the frame I will just use the drop down brackets like you were talking about for both the panhard bar and the radius rods. And just so I am clear, it is better that the panhard bar traverse along the axle as far as it can from one side to the other side (between attaching it to the axel and the frame) correct? An that that it should remain parallel to the ground at ride height?

Also, when I go to mount the coil over shocks, I can fabricate perches like you described for the radius rod ends to attach to the axle and the frame crossmember correct?

Finally, what is the best way to make sure that your rear end (axle) is correctly positioned in relation to your tranny and drive shaft when this is all done? What measurements are the most critical?

Thanks again for your time.

Brent

[powerrodsmike]

All of what you say is correct, you want to set your frame up at ride height to see where the best place for your radius rods to mount will be.

you want to do a search here for "pinion angle" and you will find a bunch of threads about setting the rear end up so the pinion angle is correctly aligned with the trans.

Later, mikey

[Frisco]

Originally Posted by 31fordcoupe

Frisco,

Thanks alot for the suggestions and help.

Can I use radius rods and coil over springs like I have pictured in my old T-bucket picture? I think it looks better and will be more at my skill level of installation.

Yes, but parallel four bars would yield a better functioning suspension when using coil overs.

Originally Posted by 31fordcoupe

Also, is the panhard bar that you are referring to that bar that parallels the axle in your last picture (runs above the pumpkin)? I believe that just goes across and attaches to the frame correct?

Yes and yes.

Originally Posted by 31fordcoupe

Finally, if I go with a coil over set up with the radius rods, how critical is the angle of the coil over shocks? Is it best that they are perpendicular to the axle? Or can they have a slight angle like is pictured in my T-bucket photo?

The angle is critical in the sense of how the coil overs function. See the scan from a Speedway catalog below. Left click on it for a larger view. For the street, I prefer them to be at about 15 degrees in at the upper end to control the side to side sway somewhat. Most all out drag cars will mount them straight up.

Originally Posted by 31fordcoupe

And just out of curiousity, what held your springs in place other than the weight of the vehicle on that T roadster pickup?

I found a set of shocks that when fully extended were slightly shorter than the Corvair front coil springs fully extended (no load on them) that I used. This is what held everything together. With the full body weight on the rear the shocks had about 60 percent of the downward travel left. This worked very well for that vehicle and rode excellent.

powerrodsmike actually covered most of the questions already. He is a full time builder and from what I have seen from photos of his work that he posted, absolutely will give you excellent advise.

Originally Posted by 31fordcoupe

Finally, what is the best way to make sure that your rear end (axle) is correctly positioned in relation to your tranny and drive shaft when this is all done? What measurements are the most critical?

Measure from the center of the rear axle to the center of the front spindles on both sides. Adjust so that they at the same length. This will get the front and rear axles parallel to each other.

Measure from a point on one side of the rear axle on the bearing flange diagonally to the center of the front kingpin on the opposite side. Do this measurement from both sides of the rear axle. Adjust so that these dimensions are the same as each other. This will get the rear axle square and centered in the frame.

With the frame at ride height on level ground and the engine leveled front to rear and side to side (place a level on the top of the intake manifold on the carb mounting surface to do this), check the angle of the crank/transmission. It will usually be in the 3-4 degree range down (direction) as this is what is built in by the manufacturers.

You can now set the pinion angle to whatever you just measured, except you will set it up (direction) the same number of degrees. i.e. engine down 3 degrees at rear / pinion up 3 degrees at front.

The offset that will often be found in the rear pinion shaft will not usually be of much concern except when a very short driveshaft is required. If a very short driveshaft is required, then the rear housing should be shortened on one side so that the pinion shaft is more centered when the rear housing is installed.

What you are attempting to yield is that the centerline of the crank/trans mainshaft is parallel to the centerline of the pinion shaft when looking from the side and/or the top.

[31fordcoupe]

Thanks again Frisco. I think I've got it all now. However, I need to get my motor an tranny bolted in place first. We just pulled out the 302 Ford that was in it with an AOD. Putting in a 454 with a Turbo 400 and I still have to cut out the old crossmembers and put in new crossmembers. So it looks like I got a little bit ahead of myself on the rear end seeing as I have to get the angle an alignment of all that correct. I should be there quick enough though and your help and Mikey's help has been immeasureable.

Do you know the best way to modify a driveshaft so I can hook it up to the tail end of a T400 and a 9 inch?

Thanks to both of you.

Brent

[powerrodsmike]

Originally Posted by 31fordcoupe

Do you know the best way to modify a driveshaft so I can hook it up to the tail end of a T400 and a 9 inch?

Thanks to both of you.

Brent

I'd find a junkyard driveshaft that fits the t400, have your local driveshaft shop it cut down to the right length then use a conversion U joint to hook it up to your rear end..

You can have one made up with all new parts as well, IIRC jegs and summit and speedway motors have some selection of new driveshafts.
There are other online places that sell those.
Later, mikey

[31fordcoupe]

Ok. Thanks Mikey.

And the questions keep on coming. LOL

I was looking over the rear part of the frame and it is obvious to me that when looking down both lines of the frame to the rear, that the drivers side frame in the very rear (the C shape that goes over the axle) is angled in towards the centerline of the frame a couple of more degrees than the passenger side is. I have placed photos in my photo area for you guys to look at. I am PRAYING that you guys tell me that it is not super critical as I DO NOT want to start tearing this frame a part unless there is no way this will work.

http://www.hotrodders.com/gallery/bu...ss=10&dthumbs=

I will let you guys look at the photos and tell me what you think. I'm praying you tell me it will be ok.

[powerrodsmike]

Nothing is ever perfectly straight. The frame can be crooked like that as long as the shock mounts are centered over the rear end and the spring installed height is close enough to have the car sit level.

Every time someone starts measuring things and trying to get them perfect, they spend a ton of time and wind up with nothing other than the personal satisfaction of knowing they made it perfect. (and if you spend any time at all around a model A, you will always find stuff that is out).

Unless it is visibly out of whack, and will be seen and noticed, I just make sure all of the attachment points are square to the axles, radius rod landing points, etc.

To give you a point of reference, an everyday alignment shop will do a 4 wheel alignment on most every DD, and as long as the wheelbase is within 1/2" from side to side and the axle offset is within 1/2" they will align the thing so it goes straight down the road, and you would never know.

We're not talking about F1 stuff here. I've never seen a frame that was perfect, even the new repro stuff is off by an 1/8 or 3/16".

Later, mikey

[powerrodsmike]

PS- your picture does not show up.

If you are concerned, you can always warm up the frame with a rosebud some and push it back straight.

Later, mikey

[31fordcoupe]

Mikey,

I shrunk the pictures down. Here they are.

Brent