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Duff's monster 4-link install *PROBLEM*

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
I have been working on installing a Duff's monster 4-link over the past few weeks and have run into an issue that we (me or Duff's) can't solve so hopefully you classic gurus can help.

We installed the 5.5" Duff's front and then started on the 4-link rear (Ford 9").

Our ride height goal is to have the rear approximately 1/2" higher than the front to account for spring settling.

With Bronco weight on the springs, the rear is currently sitting about 2" higher than in the front. It was originally 3.75" high but I think the springs have settled over the past 2 weeks. The problem with this is we can only raise the rear coil towers another 3/4".

We we have verified the following:

Front coil towers are in the correct position
Front coils are correct height (compressed and uncompressed)
Front resting at correct height (top of axle to bottom of frame 11-3/4")
Rear coil towers are in the correct ballpark position
Rear coils are correct height (compressed and uncompressed)
Rear resting high measured from top of axle to bottom of frame.
Front bumper and winch removed to verify additional weight was not an issue.

A new set of rear coils are on the way to eliminate them as a factor in case they are not compressing correctly but other than that we are at a complete loss.

My complete build thread is located here. Page 5, post 41 is where the ride height issue starts.
I plan to post it to classic in the next few days.

Can anyone offer suggestions? ;)
 

Jsp

Jr. Member
Joined
Feb 21, 2010
Messages
106
Loc.
San Jose, CA
I wish I could help but I'm sure you guys are covering everything since duff has installed these before. But if was trying to figure it out I would be leaning towards front spring overcompressing or wrong ones or maybe both rears are 7.5 springs which I doubt.
 

blazinchuck

Bronco Guru
Joined
Jul 14, 2005
Messages
3,319
I wish I could help but I'm sure you guys are covering everything since duff has installed these before. But if was trying to figure it out I would be leaning towards front spring overcompressing or wrong ones or maybe both rears are 7.5 springs which I doubt.

yeah, we've checked/double checked the front as being the right ones and the rears being what they should be.i think they are sending us another set for the rear(should be here today). we also removed the front bumper to see how much higher the front would come up(only about 1/2-3/4") not really enough to account for the difference between the front and rear. its also my understanding that the 4-link(as of now) was and is really designed as a 5.5" lift, with the use of 2" body lift(recommended). and when i compaired my cage 3.5 " fronts to his duff 5 or 5.5" lift...they are atleast 2.5" taller than mine installed, so they do seem right
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
Thought front was 7" axle to frame (stock)if thats correct 7+5.5=12.5 fronts 3/4 inch low.

really yall way over my head but.....

Lower the rear raise front you in there
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
If I lower the rear and raise the front I still end up with a lift greater than 5.5"

I wanted a 3.5" suspension lift in the first pace but the "bolt on" 4-link did not offer that option.

We are just going shave as much meat off the top of the rear coil towers as practical and the raise the up on the frame flush with the bottom of the floor and see what happens.

We are 2" high now and figure we can get about 1" with the shaving and raising. We will have to hope the rear springs settle the advertised 1/2" and I will live with the rear being 1/2" high.

This is all hypothetical and we will just have to see how it all settles in the end. Either way, I am ready for this project to move forward.
to raise t
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
I wanted a 3.5" suspension lift in the first pace but the "bolt on" 4-link did not offer that option.


I missed this as your desired lift hieght!
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
A full tank of as weighs in at 150 Lbs. I run no top and no rear seat My floors are pretty thick at about 3/16" so that should make up for the extra weight.

The rear of my rig should not shoot for the stars with an empty tank. That is slightly extreme in my opinion.

I actually used bags of blasting media and loaded them on the tailgate and it took about 300 Lbs of it to get the rear to level with the front.
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
Good question. I think that would be great, but the front and rear coils are not interchangeable so obtaining a 4.5" rear coil is not an option.
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
why are the coils not interchangeable? i have the duff upper coil brackets for the 4 link i'm building and a standard bronco coil spring fits in them perfectly.
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
it looks like their lower coil buckets sit a few inches off the top of the axle tube. you should be able to lower those
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
i talked with the duffs about their 4 link before and they told me that the 5.5" advertised lift for their 4 link was 5.5" over stock but used 3.5" springs (iirc). if you want to drop the back end you should be able to get a set of 2.5" springs for the rear.

sorry to keep posting if this information isn't helpful at all. just trying to help out.
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
Good point. I guess I just meant the springs were not the same in terms of height between the front and rear. You know, I have talked quite a bit with Duffs and am not sure why the thought of not using a 2.5" version has not come to the table. I will be sure to mention that on Monday; it's a good idea. I really appreciate the input.
 

ken75ranger

Bronco Guru
Joined
Jan 27, 2002
Messages
5,069
Loc.
Troy, NY
Good point. I guess I just meant the springs were not the same in terms of height between the front and rear. You know, I have talked quite a bit with Duffs and am not sure why the thought of not using a 2.5" version has not come to the table. I will be sure to mention that on Monday; it's a good idea. I really appreciate the input.
Before you have them send the shorter springs you might want to cycle the suspension with what you have. Ideally I'd do it with no springs and the rear of your body on stands at ride height.
It looks like the upper link mount on the axle is getting very close to the floor of the bed. A shorter spring might be too short.
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
Oh ya. I almost forgot that the coils act as the bump stops and that the truss is pretty high on the axle. I bet it would go through the floor if I went with a shorter coil. Definitely something to look at. Good catch.
 

ken75ranger

Bronco Guru
Joined
Jan 27, 2002
Messages
5,069
Loc.
Troy, NY
Oh ya. I almost forgot that the coils act as the bump stops and that the truss is pretty high on the axle. I bet it would go through the floor if I went with a shorter coil. Definitely something to look at. Good catch.
No bumpstop really isn't a good idea. You don't want to put normal coils into a bind for long term use. I'll take another look at your pics and see if I can figure an easy bumpstop solution.
 
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chuzie

chuzie

Bronco Guru
Joined
Jul 21, 2006
Messages
2,697
THanks Ken. I do have a set of the Duff's bump stops but was considering them for installation in the front but i can always get another set from the yard too if I need them.

P1020109.jpg
 

mavereq

Bronco Guru
Joined
Feb 19, 2009
Messages
2,092
now that i see this i'm glad i didn't go with this system. nothing against duff products at all. it looks like your upper links are mounted that high so that you can still get good vertical separation from your lower links, which are mounted above the axles. i'll play around with the link calculator, but it looks like they might be doing that to lower the oversteer. the oversteer is probably caused by the lack of triangulation. it looks like you have about 10 degrees max on your uppers and lowers and it should have more if you aren't running a panhard.

this is all speculation on my part. i'm setting mine up with about 15 degrees on my uppers and 25 degrees on my lowers. it's hard to triangulate the uppers because the frame is so narrow so i'm making up for it with more on the lowers.

does anyone have any experience wth this system? i'm sure it's been tested or duff wouldn't be selling it. there are a thousand ways to skin a cat.

it's definitely not ideal if you're wanting to lower it. can you post up some pics of the frame link mounts? how much vertical separation do you have at the frame? how much longer are your lower links?
 
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