Unlike the rear axle, a front axle differential is offset to one side to match up with the front t-case output. When building a three-link with a panhard bar, the location of the steering box will determine how the panhard mounts. For the common driver side steering box (without double crossover steering), the draglink and panhard will run [parallel] from the frame rail on the driver side to a point on the axle on the passenger side.
When building a linked suspension on a factory frame using a body, you often have the option of adjusting where the front axle will end up and can work on gaining tire clearance at the fenders or firewall. On a leaf spring suspension with rear shackles, the axle and tires move backwards as the suspension compresses and often sends large tires rubbing on the rear fender portion or firewall. On a front linked suspension, this will not be the case. As the suspension compresses, the axle will now move forward and the tires may end up rubbing the front portions of the fenders. How much the axle moves fore/aft will depend on the link angles, lengths, and mounting locations of the links.
Anti-Dive
Last month we discussed anti-squat in relation to the rear suspension. Up front, we have concern for a similar characteristic called anti-dive as the weight of the vehicle transfers towards the front during braking. One hundred percent means the vehicle will not dive on level terrain. You'll see from the calculator that the upper link geometry largely determines how your vehicle reacts to the forces of acceleration and braking. The geometry can cause the front end to rise or drop under acceleration. The greater the anti-dive, the less front end dive you'll experience during braking. This characteristic can also affect the manner in which the vehicle climbs hills as weight is unloaded from front to rear. With too much anti-dive, the axle may want to droop out, rather than allowing the tires to climb an obstacle. Common design targets seem to often be in the 50- to 100-percent range.
Instant Center
If you draw a line through the upper and lower links (viewed from the side) and extended them rearward, the point at which they would intersect in space is the instant center. This is the point about which the suspension linkage will act. Imagine you draw a line from the front tire contact patch to a point where the height of the COG and the rear axle centerline meet. If the instant center lies below this drawn line, you have less than 100-percent anti-dive. If it lies above the line, you have greater than 100-percent anti-dive.
Roll Center
Last month we talked about roll center height being the height at which the body/chassis "pivots" with respect to the axle and how it helps determine the amount of body lean you experience. In the case of a three-link setup, the roll center height is the height of the center point of the panhard bar. Again, if this point is fairly low, then you will get increased body roll, or lean. If this point is higher, then body roll will be less.
Suspension Droop
One thing to watch for with a linked system is the need to limit droop. Allowing the coilovers or shocks to stop the downward travel can cause them to become damaged. Use of limiting straps at the axle ends is often a good idea for vehicles that often see conditions (jumping) where the front axle drops all the way out. For those concerned more with articulation and less about full droop travel, a center mounted limit strap may suffice. In either case, the limit of your driveshaft angular travel should be checked against how far the axle is allowed to fall.
Some good points to remember when setting up a front 3-link are:
(1) Make the front links as reasonably long as you can (frame constraints and ground clearance will dictate here)
(2) Try to keep the top link near parallel to the ground
(3) Try to maximize vertical link separation at the front axle (within reason; 8 to 12 inches is a good target)
 This front suspension has...  This front suspension has large vertical separation between the upper and lower links. The greater separation helps counter the forces tending to rotate the axle housing under acceleration and braking. Note also that the upper link mount on the axle is offset to the driver side and the frame end of the link is over near the frame rail to allow the link to clear the oil pan as the axle travels upward. |  In general, steep link angles...  In general, steep link angles should be avoided when possible. Steep links can make the front of the vehicle want to expand the front suspension under braking which can result in strange road handling. |  You'll get the best axle control...  You'll get the best axle control by spreading your axle link mount points as wide as possible. However, be mindful to check the clearance between your tires and links at full steering lock. Consider your wheel offset and largest tire you intend to use, as well as the steering limits of the axle you're using. |
 Here is a typical three-link...  Here is a typical three-link where the upper link is mounted above the differential. Location where this link will fit may depend on the oil pan shape and/or the location of exhaust pipes that run between the engine and framerails. It's good for lateral location of the axle to have the lower link horizontal separation a bit wider at the axle than at the frame, but the frame separation may be limited by a tire rubbing at full steering lock. |  This example of a three-link...  This example of a three-link setup may be fine for street use but could be improved upon for off-road use. The lower link mounts at the axle hang very low and the long link lengths may be subject to bending and dragging on drop-offs. Use heavy (>0.25-inch wall) DOM tubing for lower links that may come in contact with rocks. |  One struggle with designing...  One struggle with designing a front solid axle suspension is that of getting the differential and oil pan to clear when the suspension is fully bottomed. While it looks like the two are close in this photo, the axle really lies a good ways in front of the oil pan. On a custom built vehicle you have more latitude to move components, but with a bodied vehicle, the fenderwells or other parts may prevent you from pushing the axle so far forward. |
 Here you can see the two links...  Here you can see the two links on the passenger side of this buggy. The vertical separation at the axle end controls axle roll and the angle between them (as viewd from above) provides some lateral positioning. The panhard bar in the foreground is the primary means of positioning the axle from side-to-side. |  Here's a front side view of...  Here's a front side view of a triangulated 4-link front suspension. One upper link is mounted above the differential and the other is mounted to a tower on the axle tube. One consideration when mounting to the axle tube is the possibility of the leverage applied by the upper link causing the tube to spin in the differential housing or in an extreme case having the axle tube fracture. Adding a bridge truss across the top of the axle can help spread the loading from the link force. |  With all the parts tack-welded...  With all the parts tack-welded in place, it's a good idea to cycle the suspension to fully compressed and also fully articulated from side to side. Tire and linkage clearance should also be checked with the steering fully turned in both directions. There's a lot of moving pieces to watch for and it's best to find any problems now than later when making changes to the suspension is more difficult. You'll also want to check that you get full lock steering under all conditions because as the axle falls away from the steering box, the draglink angle may prevent full steering under extreme droop or articulation. |
 Note that the draglink and...  Note that the draglink and panhard bar are perfectly parallel on this truck. This will help to reduce bumpsteer as the axle should resist forcing the tires to turn as the suspension moves up and down. However, the steep linkage angle will still cause the axle to push sideways with respect to the chassis as the suspension moves. |  This beefy panhard bar sits...  This beefy panhard bar sits very near level with the suspension at ride height. This helps keep bumpsteer to a minimum. However, note that leverage forces are high where the extended panhard brackets meet at the axle and frame, so reinforcement here is prudent. |  It's a good idea to be mindful...  It's a good idea to be mindful of link bracket locations with respect to clearance and to the forces that will be placed on them. The spreadsheet can help with calculating the expected load forces. Sometimes links can be bent for clearance but should be upgraded in strength to compensate for the bend weakness. Also, a bent link will still retain the same geometry behavior, good or bad, as that of a straight link. It's the angle and distance between the two end points that matter, not the shape of the rod connecting them. |
 Early Ford Broncos use a coil...  Early Ford Broncos use a coil spring front suspension with two large radius arms. The arms are held fast to the axle housing with bushings to keep the housing from rotating. This, combined with a panhard, completes the suspension. These setups offer decent but not great articulation due to the arms binding when twisted too much. Installing longer arms, such as shown here, helps increase the flexibility of the suspension but still won't quite offer the range of movement of a fully linked setup. |  For serious rock crawlers...  For serious rock crawlers running linked front suspensions, it's not uncommon to see their winch rope clipped onto the front axle. This allows the ability to tighten down the front suspension and constrict axle droop in situations such as on steep climbs, where the suspension may want to unload too much. | |