Track Bar Relocation


Back to Grand Tech
North American Grand Cherokee Association
Your one stop source for Jeep Grand Cherokee Information

Track Bar Relocation

By Alan Ratcliffe

There are many ways to do this, but ...

... I wanted to make sure any potential drawbacks were thoroughly resolved. After doing the Front>Rear spring swap I was still concerned with the rear trackbar. The axle had a significant shift to the passenger side of the ZJ, and the whole setup seemed to be binding before full droop was reached. So I put the ZJ back up on stands, removed the rear springs, laid out a number of baselines and then began the process of making key measurements throughout the full suspension travel from full compression to full extension. From there, I then laid out these same points full-scale on the drawing board and plotted relative movement and the effect of making given changes to the geometry. After exploring various alternatives, I settled on some radical surgery as the optimum means to properly correct the suspension geometry.

Key Discoveries

Some of the critical areas which determines how the rear track bar moves, and what could and should be done to correct the geometry for 3" or higher lifts.

the OE trackbar is 30.75" long measured center to center.

At full compression (against the stops) the track bar is essentially horizontal. In other words, the height above ground to the center of the axle and frame mounts is the same. At any amount of downward travel, the axle end mount follows an downward arc with a radius of 30.75". As the axle moves down, it must also move towards the passenger side of the vehicle.

At reasonable track bar angles, with respect to the horizontal (i.e. stock) the amount of sideways movement is relatively small. This shift does begin to grow substantially as the angle grows. This chart will illustrate the impact with the OE track bar and anchor points.

Relative Position	Downwards Travel from the stop	Angle from Horizontal	Sideways shift to passenger side
Against the stops	0	0.0	0
OE ride height	3.125	-5.8	0.2
3" lift height	6.125	-11.5	0.6
Full droop with OE track bar	9.50	-18.0	1.5
Full droop with track bar disco'd	10.75	-19.5	1.8

The control arms obviously have a limit in the amount of sideways deflection they will permit without binding, that limit being empirically determined to be 1.5".

At full compression, the axle end track bar bracket comes up beside the frame with about 5/8" of clearance. To avoid any chance of hitting, this limits the adjustment available with an aftermarket track bar. Assuming you want to maintain 1/8" of clearance between major components that move with respect to one another, we can calculate the same table above for a adjustable bar with a length of 31.25" and OE anchor points..

Relative Position	Downwards Travel from the stop	Angle from Horizontal	Sideways shift to passenger side
Against the stops	0	0.0	-0.5
OE ride height	3.125	-5.7	-0.3
3" lift height	6.125	-11.3	0.1
Full droop with track bar	10.75	-19.1	1.2

The other alternative is a bolt-on bracket which relocates the axle end anchor point higher to reduce the angle of the track bar at full extension. Based on my measurements, for a bolt-on bracket to work, the relocation would have to be at least 2.5" upwards to be fully clear of the existing bracket. Consideration then must be given to clearance to the floor pan at full compression, and possible interference with the exhaust system. Assuming it could be accomplished, we can again calculate the table for a bolt-on axle end 2.5" relocation bracket with the OE track bar.

Relative Position	Downwards Travel from the stop	Angle from Horizontal	Sideways shift to passenger side
Against the stops	0	+4.6	-0.1
OE ride height	3.125	-1.2	0.0
3" lift height	6.125	-6.8	0.2
Full droop with track bar	10.75	-14.6	1.0

I then looked at relocating the frame end anchor point due to concerns over interference, particularly with the axle-end relocation bracket. I wanted to eliminate binding potential as much as possible, clear all the other chassis components and retain the OE track bar for ease of service and ride quality. The key was to have the smallest relocation possible that would provide acceptable performance while minimizing the possibility of interference. Based on layouts, I determined that I would locate the frame end anchor 1" lower and 0.5" inboard of the OE location. This appeared to meet the required goals. Calculating a new table, the results for this relocation with the OE track bar are:

Relative Position	Downwards Travel from the stop	Angle from Horizontal	Sideways shift to passenger side
Against the stops	0	+1.9	-0.5
OE ride height	3.125	-4.0	-0.4
3" lift height	6.125	-9.6	-0.1
Full droop with track bar	10.75	-17.5	0.9

How it was accomplished

Fabricate a new bracket addition from a piece of 1/8"x3" mild steel. The inside width of the C-form should be 1.625" to match the track bar end. Additionally, two straps were cut from 1/8"x1" mild steel to serve as reinforcement plates and allow either the OE or the revised location to be used. The sketch below generally shows how the finished part is supposed to assemble. It becomes clear from the sketch the reason why this is an involved modification to make, if you are to achieve the greatest benefit with the smallest dimensional change.

After unbolting the track bar, you have to take a torch to the OE bracket, making a horizontal cut completely around the bracket even with the centerline of the OE anchor bolt hole. Then position the new bracket, and secure in place using the anchor bolt to clamp the new bracket to the old bracket. Then MIG weld all around, using the heavy lines on the sketch as a guide.

Areas of Interference

The only problem I encountered following the installation was contact between the track bar and the 3" Mopar Performance Cat-Back exhaust pipe. There is a clamped joint right alongside where the track bar passes. After assessing the tightness of the joint, I decided to remove the clamp and secure the pipe connection with a 3/16" Pop-Rivet to prevent movement. Then I made some modifications to the rear exhaust hanger to hang the pipe about 1/2" closer inboard than the stock location. The combined effect of these two additional modifications eliminated interference under all conditions. I suspect, but cannot confirm, that the smaller OE exhaust would not have the same problem.

Conclusions

Given the above results, you can see how the geometry is better balanced by moving the frame end anchor both downwards and inwards. Total lateral movement is less than the result of a longer trackbar, but greater than an axle end relocation bracket. However the combined impact of the relocation is to keep the range of displacement centered more closely around the natural center of the vehicle. This becomes important when considering wider tires, and interference in the fender wells becomes of greater concern.

This is not a modification that should be considered unless you either have, or have access to, the necessary skills and equipment. The track bar transfers significant lateral loads to the frame when cornering. The welding must be on a high order in terms of quality, both visual and structural.

Send comments to grandtech@nagca.com

North American Grand Cherokee Association

www.nagca.com