Front Suspension Wizard Input Needed

[AZJeff]

I have been chasing a "sproinging" sound in my front suspension for a while, and did a whole bunch of upgrades/repairs trying to eliminate it.   These included:

 

1.  new control arm bushings (and they bolts are torqued to spec., and maybe then some)

2.  new spring isolators

3.  new bump stops (jounce bumpers)

4.  new track bar ball joint end

5.  new shocks

 

All of this has been to no avail, (not that those parts didn't probably need to be made better anyhow.)

 

But my issue remains.  When I go over a curb (or other similar road bump), I get a "sproing" type of sound from the left front wheel area.   I did some searching around under the front end, and I noticed two odd things:

 

1.  the front springs are curved/arched slightly forward when the vehicle is at normal ride height.   (These are "Rusty's" brand springs with a nominal 4 inch lift, but I cut about 3/4 of a coil off to achieve a slightly "nose down" attitude on the truck when unloaded.)

2.  the clearance between the coils and the OEM style track bar bracket is really pretty small, at about 1/4 inch.   I attached a picture that shows the clearance.  I repainted the two parts, and took it for a test drive over some curbs in the neighborhood, and when I got back, I could see there is some paint rubbed off both the spring and the bracket.

 

This is not my first rodeo with the XJ/MJ, so I checked by control arm lengths.   The lift was on the Jeep when I got it, so I wasn't sure what to expect.  I found the UCA has a length of 15.8 inches, and the LCA's are 16.2 inches.   From what I know about recommended lengths for a 3.5-4 inch lift, this makes the UCA's too long by about 0.8 inches.

 

I know that changing to a shorter UCA could cause the lower spring seat to rotate rearwards, and that would decrease the forward arch of the spring.  But would it remove the close fit between the spring and the track bar bracket?

 

Input from knowledgable XJ/MJ suspension wizards is appreciated here.   If I am going to buy new parts, I want them to fix the issue once and for all.

 

 

Clearance.pdf

[Eagle]

Didn't Hornbrod have some photos and details of a modified track bar mount to alleviate this problem?

[JustEmptyEveryPocket]

Eagle, I thought Hornbrod did the different sway bar mounts. Like THESE HERE.

[Eagle]

1 hour ago, JustEmptyEveryPocket said:

Eagle, I thought Hornbrod did the different sway bar mounts. Like THESE HERE.

 

You are absolutely correct. I was reading and writing "track bar," but thinking "sway bar."

 

It happens -- you'll find out when you reach my age.

[gogmorgo]

I've had a couple "sproing" sounds from front axles. It was mostly things coming into contact with the coils I would say. One time the sway bar got bent in a way the end link was getting shoved into it Another time again it was the end link hitting it, but in this case because the bottom coil had broken off and the spring had found a new home up against the C of the axle.

As to whether or not you have the same thing going on, I can't say. But it's something to look at I guess. 

[AZJeff]

32 minutes ago, gogmorgo said:

I've had a couple "sproing" sounds from front axles. It was mostly things coming into contact with the coils I would say. One time the sway bar got bent in a way the end link was getting shoved into it Another time again it was the end link hitting it, but in this case because the bottom coil had broken off and the spring had found a new home up against the C of the axle.

As to whether or not you have the same thing going on, I can't say. But it's something to look at I guess. 

I already took out the springs, and inspected them when I replaced the coil isolators where the top of the spring seats on the chassis, so I know the springs are fine.   (Other than the fact that they are bowed slightly forward when installed, resulting in the close proximity to the track bar bracket.)

 

I am positive that the XJ/MJ, as designed, had more than 1/4 inch of the clearance between the outside diameter of the coil and the track bar bracket, and that the bowing of the springs is not normal.   

 

I am leaning towards one of two explanations for why the coil spring is bowed/arced forward:

1.  crappy Rusty's springs that are not straight.

2.  forward can't to the lower spring seat, causing the spring to be tilted forward on it's bottom end.  (The upper and lower seats are, in essence, not parallel at normal ride height.)

 

Since the spring is NOT bowed when I remove it from the vehicle (it rolls on the concrete floor quite nicely), I am discounting explanation #1 above, and am tending to think #2 is my issue.  

 

I am thinking the canted spring seat is being caused by the axle being tilted forward beyond the recommended/designed angle.   Since my UCA's are longer than recommended for a 4 inch lift (but my LCA's are at the recommended length), the longer UCA's are pushing the top of the axle forward and causing the axle tilt.

 

I am inclined to buy new UCA's, but want to make sure that investing in some good aftermarket ones will actually fix the issue, so I am seeking experienced inputs here.

[Gat'79]

I already took out the springs, and inspected them when I replaced the coil isolators where the top of the spring seats on the chassis, so I know the springs are fine.   (Other than the fact that they are bowed slightly forward when installed, resulting in the close proximity to the track bar bracket.)
 
I am positive that the XJ/MJ, as designed, had more than 1/4 inch of the clearance between the outside diameter of the coil and the track bar bracket, and that the bowing of the springs is not normal.   
 
I am leaning towards one of two explanations for why the coil spring is bowed/arced forward:
1.  crappy Rusty's springs that are not straight.
2.  forward can't to the lower spring seat, causing the spring to be tilted forward on it's bottom end.  (The upper and lower seats are, in essence, not parallel at normal ride height.)
 
Since the spring is NOT bowed when I remove it from the vehicle (it rolls on the concrete floor quite nicely), I am discounting explanation #1 above, and am tending to think #2 is my issue.  
 
I am thinking the canted spring seat is being caused by the axle being tilted forward beyond the recommended/designed angle.   Since my UCA's are longer than recommended for a 4 inch lift (but my LCA's are at the recommended length), the longer UCA's are pushing the top of the axle forward and causing the axle tilt.
 
I am inclined to buy new UCA's, but want to make sure that investing in some good aftermarket ones will actually fix the issue, so I am seeking experienced inputs here.

I have this spring problem also. Looks bowed, but when taken out they are straight. The sway bar bar attached to the links touch the spring.

I thought it was that I have a lift and just needed longer links.

Sent from my LYA-L29 using Tapatalk

[AZJeff]

2 hours ago, Gat'79 said:

I have this spring problem also. Looks bowed, but when taken out they are straight. The sway bar bar attached to the links touch the spring.

I thought it was that I have a lift and just needed longer links.

Sent from my LYA-L29 using Tapatalk
 

Your problem is an easy one to fix.   The link mentioned above (and reposted below) will do the trick, but you might need to fab your own relocating brackets.  I have already done this on my MJ:

 

 

 

[JustEmptyEveryPocket]

If it was my money, I would buy adjustable arms. Like THESE. Then I could dial everything in myself. Personally, I set my caster to about 10 degrees. I know that ~7* is stock, but I like the road feel of a little more angle. This is only possible because I have adjustable uppers and lowers. Not everyone's cup of tea though.

[AZJeff]

14 hours ago, JustEmptyEveryPocket said:

If it was my money, I would buy adjustable arms. Like THESE. Then I could dial everything in myself. Personally, I set my caster to about 10 degrees. I know that ~7* is stock, but I like the road feel of a little more angle. This is only possible because I have adjustable uppers and lowers. Not everyone's cup of tea though.

Yeah, I think I am going to go that route.

 

It will get me the correct lengths, and a bit more caster, which, as  you say, is a good thing in my book as well.   Thanks.

[Eagle]

21 hours ago, AZJeff said:

I am leaning towards one of two explanations for why the coil spring is bowed/arced forward:

1.  crappy Rusty's springs that are not straight.

2.  forward can't to the lower spring seat, causing the spring to be tilted forward on it's bottom end.  (The upper and lower seats are, in essence, not parallel at normal ride height.)

 

 

Number 2 for the win. Bowed springs after a lift is very common. Think about the geometry involved. The spring seats were designed so the springs would be straight with the vehicle at stock height and the axle at the specified caster angle. Now you throw in a lift, so the springs are longer and the spring seats are farther apart, you change the control arms to shove the axle forward by who knows how much, and the caster angle is reduced.

 

Getting the caster angle somewhere close to spec should help. If that doesn't help enough, then you need to shorten both the upper and lower control arms.

[Gat'79]

Your problem is an easy one to fix.   The link mentioned above (and reposted below) will do the trick, but you might need to fab your own relocating brackets.  I have already done this on my MJ:
 
 
 

I will definitely be doing this when I get back.

Does someone have the link for the rear sway bar installation?

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[dasbulliwagen]

I agree with adjustable uppers and lowers, as well as sway bar drop brackets which I got from Rubicon Express on Amazon. I bought Core 4x4 control arms. Theyve been really good so far and can be had in multiple colors.

 

[AZJeff]

Heads up to those who offered suggestions:  I put some adjustable arms on my MJ, and set the length and caster to match the recommendations for a 3.5-4" lift.  My spring interference issue is gone, and the truck rides quietly.  (Or at least as quietly as an MJ can ride.)

 

Thanks to all who commented.

[Pete M]

those lengths are the starting point.  an alignment might get it even closer to ideal