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You are here: Home Tech Articles & Tutorials Steering / Suspension / Brakes '65-'79 Truck Suspension Lowering Basics
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'65-'79 Truck Suspension Lowering Basics

How can I lower my '67-'72 pickup?

   For the back end, there are several options.

  • You can have the rear springs professional de-arched (NEVER heat the springs!), but this will probably require relocating the shackles and spring hangers.

  • You can flip the rearend over which will place the spring pads on the bottom of the rearend housing, lowering the truck about 5 inches. However, it will probably be necessary to add a C-notch in the frame to prevent the rearend housing from hitting the frame under extreme suspension travel.

  • Another way of gaining 1/2" to 1" drop is by removing the helper spring, the thickest spring at the bottom of the spring pack. Keep in mind you will lose payload capacity.

  • You can also cut the factory rivets from the front bracket on the rear spring, flip it over, and bolt it back down (requires drilling some new holes) which will lower it 4-5 inches. When done, there is no change in ride quality, though the axle bumpstops are getting close to hitting the frame during suspension travel. The only other thing you might have to watch for is altering the pinion angle, but this will also change by doing an axle over. You might be OK, you might not. You will need to check your pinion angle after you flip the hanger, and if the pinion angle has been altered too much, it can be easily corrected by using angled shims between the leaf spring and the perches on the rearend housing. These can be obtained from an aftermarket source such as Jegs or Summit Racing.

     Depending on the amount of drop in the back end, be sure to watch the bed lip up inside the wheelwell for tire rubbing. If lowered too far, it can cut into the tire's tread.

     For the front, you can cut the front springs a bit, but don't get carried away, as this will the affect the camber, which can only be adjusted by a specialty shop by actually bending the I-beam. Cut 1/2 a coil per side at a minimum to a maximum of 2 coils. Why? Well, the design of the Ford I-beam suspension system means the I-beam rotates around the beam's pivot point. As the beam travels up and down, the camber changes dramatically. Cutting the spring will cause the tops of the front tires to lean inwards, affecting steering control. Moderation is the key here.
     Another option is to use lowering springs...either standard or progressive-rate. I've been told that the standard lowering springs tend to have a harsher ride than the progressive-rate springs.
     The PROPER way to lower a front end is by using aftermarket drop beams. AIM and DJM both make drop beams to replace the standard Ford I-beams and both also sell the necessary parts to lower the rear end. If you want wider wheels and disc brakes, go with the DJM beams, as these are 1-1/2" shorter in length. AIM has beams for the F100 and the F250/F350 trucks.

  A steering dampener is recommended to reduce the bump-steer effect.

     If money is no object and this is strictly a cruiser, another option is to install the Mustang II IFS. You can buy this in kit form from several vendors and have an almost limitless set of options as to drop amounts, spring rates, bolt patterns, etc.

Flip kits - Flip kits are a popular way to lower the rear of your truck. These kits come complete with hardware and all of the necessary components to do it yourself. Changing the position of the leaf springs under the rear axle allows for a lower ride height. AIM axle relocators come with longer U-bolts, spring pads and spacer blocks.
(Photo courtesy of AIM Industries Inc.)

C-sections and frame notches - Dropping your truck more than 4-inches in the rear will require a C-section. Drop it to the rocker panels and you will need an entire frame section that will protrude through your truck's bed. Installation of a frame section needs to be welded in and done as straight as possible. A C-section can be bolted, but it's preferred to weld them in for extra security. Depending on how low you want to go, AIM manufactures a variety of C-sections and frame notches to add clearance for your truck's rear axle.
(Photo courtesy of
AIM Industries Inc.)

Drop Beams - AIM's I-beams for Fords are strong and lower the vehicle 3-inches. DJM's Dream Beams for '65-'79 pickups are pictured here as well.
(Top Photo courtesy of AIM Industries Inc.)
(Lower Photo courtesy of DJM Suspension)

Prices: $450-$600

Drop Leaf Springs - The easiest way to drop your truck's rear is with a set of these springs and perhaps a set of lowering blocks. These springs are new steel leaves that lower your ride 2-3 inches. When used with the AIM flip kit, the combination can lower your vehicle down to 5-6 inches.
(Photo courtesy of AIM Industries Inc.)

Ford I-beam tie rod relocater - Relocates tie rods to allow use of lowered I-beams
NOTE: It's recommended you use the AIM tie rod relocater over the DJM version. The AIM is fastened at 2 points and the DJM is basically just a shim -and looks prone to flex and wobble.
(Photo courtesy of AIM Industries Inc.)
Leaf Spring Hangers - Hangers install on front of leaf spring
(Photo courtesy of AIM Industries Inc.)
Lowering Spring Shackles - These AIM shackles lower 2" & install at the rear of the leaf spring. DJM also makes the rear shackle and spring relocaters and they have more options.
(Photo courtesy of
AIM Industries Inc.
 
Aligning the Twin I-beam suspension

One thing to always check on Ford Twin I-Beam suspensions is ride height. If the front tires show camber wear and the ride height is below specs, you can bet the springs are sagging. And since the springs play a critical role in determining ride height (which affects camber), it doesn’t make much sense to make a camber correction until the underlying problem has been fixed. The trick here is to replace or shim the sagging springs. If that fails to bring camber back within specs, you’ll have to do the following:

If the Twin I-Beam axles are the forged variety, which were used from 1965 through 1981, camber can be corrected by bending the axle with a hydraulic ram. To make a make a positive camber correction, a rigid work beam is slung under the axle from a pair of clevis blocks. A hydraulic ram is then placed under the middle of the axle. When pressure is applied, the ram bends the axle upward and tilts the knuckle down to increase camber. A slight amount of overbending is usually needed to compensate for spring-back in the axle. A negative camber correction is made by removing the outboard clevis block and inserting a spacer between the work beam and axle. The hydraulic ram is then repositioned directly under the inner axle bushing. When pressure is applied, the work beam bends the outer end of the axle up which tilts the knuckle and decreases camber.

Another thing to watch out for on Ford F150 2WD pickups with the Twin I-Beam front suspension is rear ride height. Ford says any deviation in rear ride height with respect to stock ride height should be taken into account prior to aligning the front wheels. If the bed of the pickup sits higher or lower than stock because of helper or overload springs, or because of modifications that have been made to the vehicle (a wrecker, dumpster, towing a fifth wheel trailer, etc.), then the change in ride height and frame angle need to be computed to compensate for its affect on front caster and camber. Refer to a Ford manual for the ride height and frame angle caster/camber correction chart.

Information for this page was possible with contributions from the following:
Classic Truck World
Trevor the CACWBY
AIM Industries Inc.
DJM Suspension
 

 
You are here: Home Tech Articles & Tutorials Steering / Suspension / Brakes '65-'79 Truck Suspension Lowering Basics


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