Overcoming the Shortcomings of the Stock
Suspension and Frame

The suspension on old trucks gets a lot of attention. To be specific, modifications to the suspension get a lot of attention in enthusiast magazines and websites. Independent Front Suspension has been popular on old trucks for many years because of the smooth ride it affords. On the other hand, many people do not mind the rougher ride of a straight axle. Some folks even consider it charming.

Whether you modify your suspension radically, such as with IFS, or slightly alter the stock suspension with power steering or disk brakes you should know how your changes will affect the frame. The reason for that is because the changes that affect the frame will affect the way the truck rides and handles. In all the articles I've read on suspension upgrades I don't think I've ever read one that mentioned the frame as part of the suspension.

The suspension consists of a few basic parts:

1.) The tires. Not everybody thinks of the tires as part of the suspension but the entire truck rests on them. Hard tires will feel different as you drive than softer tires. Radial tires will feel different from bias ply.

2.)The axle. The wheel has to attach to the frame somehow. Early trucks had a straight I beam axle in front.

3.) The springs. Old trucks have leaf springs front and rear.

4.) The shock absorbers

5.)The frame. Yes, the frame is part of the suspension. If you have IFS then the frame's role is that of a platform for the rest of the suspension. If you have an original suspension the frame is an active and vital part of the suspension. It twists as you drive over bumps, believe it or not.

6.)The steering should be mentioned here as well. It doesn't technically have anything to do with suspending the truck, but it works in tandem with the suspension in controlling the truck.

Here are some common issues concerning the frame and suspension. Information here is based on personal experience, experience of "old farts" I know, and experience of readers of this website. Much of the information is debatable but it's always good to be able to gather as much information as you can about a subject before you make a decision.

To box or not to box: Is stronger always better?

Myth: Boxing reinforces the frame, which is always a good thing. Better safe than sorry.

Fact: True, boxing reinforces the frame. That's not always what you want though. In fact sometimes it will do more harm than good.

Explanation: Old truck frames are made of C channel. Boxing them reinforces the metal and makes the frame stronger where the reinforcement is. Since stronger is better, we should all box our frames, right? Probably not: If your truck is stock you should leave the frame alone. The frame flexes and twists down the middle, which sounds scary to some people but it's designed to do it. And it does it a lot! If you lay a frame flat on the ground and pick up 1 corner, the other side won't lift until the side you're lifting is well in the air. Still think there's something wrong? Look at all the joints in the frame: Do you see any welds? No. All the crossmembers are riveted in place. If they were welded they wouldn't allow the frame to twist. Also, do you see an X member? No, that also wouldn't allow the frame to twist. If you keep the frame from twisting, your ride will be much worse on a stock suspension. If you don’t see why that would be a problem, try to imagine driving a brick. What if you carried a heavy load in your truck with a frame that wouldn't twist and do its job? The stiff suspension and weight from the load would crack the frame in very short order.

There are times, though, when boxing would be a good thing. Hopefully it's obvious that boxing is absolutely necessary if you have IFS. An IF needs a rigid platform to attach to so it can do all the work. IFS on a flexing frame will work against itself and will eventually crack the frame (not to mention that you won't get the smooth ride you're after). If you are planning IFS then you're probably asking yourself exactly what modifications to the frame need to be made. Here's what the old farts tell me: Use a fully welded frame and box it from the front to rear suspension. Add an IFS crossmember (obviously) and an X member (from about the firewall to the center crossmember). Overkill? Who knows, but this frame will twist very little and it duplicates the setup found in most hotrods and passenger cars. The old farts say that if you modify the frame in this way the truck will handle like a modern F150.

As stated earlier, the steering cannot be ignored when discussing the suspension as they act in unison to control the vehicle. If you have IFS and have installed it correctly you will probably have few problems with steering. If you have an original front suspension you may have some issues to deal with. Stock trucks are notoriously bad handlers, which is why there are so many IFS conversions (well, that and the enthusiast magazines promote IFS swaps ad nauseum but that's a different topic).

Steering is where the flexing frame can bite you on the butt. When you turn the steering wheel you are transmitting force through the gearbox, steering arm, drag link, axle, tie rod, and springs to the frame (which flexes in response). Somewhere in that chain of events the desired response happens and the wheels turn. When you straighten out the steering wheel after your turn, the force stops and anything that flexed returns to it's previous orientation. This can make for quite a shaky ride. Some parts contribute to this more than others. One very thorough front end man was reported to make the following modifications to minimize handling problems due to flexing. I've never seen them used so I can't attest to their effectiveness. Think it through, understand the consequences, and talk to experts before doing this on your own truck.

1.) Reinforce around the steering box to stop the frame from flexing in and out.

2.) Arc weld a 3/8 rod on the drag link side of the steering arm. The steering arm flexes a lot. Make it wider in the direction of the flex and contour it. Weld it full length. You are basically making a new steering arm.

3.) Make sure there is zero backlash everywhere. Rebuild the steering box if necessary (and it usually is).

4.) Selecting the right shock absorbers will have a positive effect on handling. Shock absorbers designed for IFS may physically fit your truck, but a solid axle moves differently than IFS and requires a different shock absorber for optimal results. Finding the "right" shocks could be a challenge. If one were inclined to experiment to find the right setting, adjustable tubulars could be great.

5.) Tire choice and wheel alignment can make a difference. Many people claim that radial tires are softer and give a better ride than bias ply. Radials may be able to be adjusted with more toe in if the steering feels loose, though not all radials will tolerate the increased toe in. Bias ply tires may need more toe in and caster than the manual says. How much more is up for debate. More caster will make the truck harder to steer, which brings us to the next section--power steering.

Elsewhere on this website is a detailed explanation of 3 popular power steering adaptations for stock suspension: Toyota 4x4, Ram Assist, and GM style.

1.) The most popular seems to be the Toyota 4x4 swap, which is also available in non-power form. Since the Toyota box works in the same way as the stock box, it retains any weakness that the stock setup had.

2.) Another popular power steering setup is the ram assist type. It utilizes the stock steering box and bolts to the axle and tie rod. This also keeps all the inherent problems in the stock setup and it also can magnify their effects, particularly a sloppy gear box (especially in conjunction with the stock 18" steering wheel). Handling above 55 mph can be very temperamental. There are unsubstantiated rumors that the ram assist will act as a hydraulic press and damage the frame, but the reports may be exaggerated. The weak point in the system is probably the tie rods so if anything would be damaged it would be them. They should at least fail first and give a warning.

3.) The GM power steering eliminates the stock box and drag link. It uses a cross steer setup which adds a second tie rod from the steering arm to the passenger side front wheel. Think about that. This is a case where you are likely turning the steering box into a hydraulic press, and it's pressing against your frame! Bob's F100's claims that this will tear the frame, especially if there is repeated oversteering.

Remember that much of what has been stated here is theoretical. There may be valid arguments against any of this information. If you have one I'd love to hear it. Most important of all, don't go and modify your truck based solely on anything you read on this, or any other, website. This page is merely intended to spark an idea. It's not a how-to! You should thoroughly investigate and plan any modification to the suspension of your truck.

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Copyright 1996-2004 Dan Wentz