How well-designed is the Duff 4 link?

[68rustbucket]

The rear crossmember will need to be cut and moved. It isn't an issue for me about fuel tank interference, I'm running propane tanks in the bed. I'm not familiar on how to do 4 link calculator, but just wondering if links would need to be lengthened.

 

[Monster Mike]

The rear crossmember will need to be cut and moved. It isn't an issue for me about fuel tank interference, I'm running propane tanks in the bed. I'm not familiar on how to do 4 link calculator, but just wondering if links would need to be lengthened.

I wouldn't recommend lengthening the links. Let's see how far back the frame mounts can be slid back before we completely change the geometry.

I'll check it out when I get back to the shop and let you know.

 

[5001craig]

I don't know anything about suspension geometry. So I started looking at the calculators online and got even more confused. So I put this same question to guys that are very knowledgeable on this topic and got positive thoughts. I know a guy that put a Duff 5.5" 4 link on his EB with no body lift. It was much more complicated but he likes it.

I wanted to 4 link my EB for excellent axle locating as well as maintaining (and improving) articulation. This thing works well and is extremely beefy. I do not like the body roll of another custom designed triangulated 4 link I rode in so I went with an antirock swaybar that I modified to go around the upper shock mount.

I also went with the adjustable coil buckets pretty much just because I already had them. It was one of my better ideas as I did the kit with the body off the frame and when we put the body on I dropped the bucket on hole or 1" to raise the rear slightly (it was squatting just a tad). I measured a gazillion times but didn't put the buckets in the exact spot they should have been. Having the ability to adjust was perfect.

I had to limit the travel with straps but it goes way down without them. I actually went conservative on the straps but it works great.

Putting the axle in exactly the correct spot was the hardest part for me. I was happy when I was at this point (pic was before I modified the coil bucket):

And just one more before I cut off the arms on the coil buckets.

 

[68rustbucket]

I wouldn't recommend lengthening the links. Let's see how far back the frame mounts can be slid back before we completely change the geometry.

I'll check it out when I get back to the shop and let you know.

Thanks Mike!

 

[68rustbucket]

I don't know anything about suspension geometry. So I started looking at the calculators online and got even more confused. So I put this same question to guys that are very knowledgeable on this topic and got positive thoughts. I know a guy that put a Duff 5.5" 4 link on his EB with no body lift. It was much more complicated but he likes it.

I wanted to 4 link my EB for excellent axle locating as well as maintaining (and improving) articulation. This thing works well and is extremely beefy. I do not like the body roll of another custom designed triangulated 4 link I rode in so I went with an antirock swaybar that I modified to go around the upper shock mount.

I also went with the adjustable coil buckets pretty much just because I already had them. It was one of my better ideas as I did the kit with the body off the frame and when we put the body on I dropped the bucket on hole or 1" to raise the rear slightly (it was squatting just a tad). I measured a gazillion times but didn't put the buckets in the exact spot they should have been. Having the ability to adjust was perfect.

I had to limit the travel with straps but it goes way down without them. I actually went conservative on the straps but it works great.

Putting the axle in exactly the correct spot was the hardest part for me. I was happy when I was at this point (pic was before I modified the coil bucket):

And just one more before I cut off the arms on the coil buckets.

Thanks for the info! Looks good. Where did you get the adjustable coil buckets?

 

[5001craig]

Thanks for the info! Looks good. Where did you get the adjustable coil buckets?

I saw them for sale used here on the forum in the classifieds. Thought it was a cool idea and bought them. The sat for a year or so until I remembered I had them. Lol

Ballistic Fabrication sells them. Mine were made for a Heep but they may make them for an EB now.

 

[68rustbucket]

5001,
are you running full width or stock EB rear axle?

 

[chuzie]

M95 skyjacker shocks took care of my sway issues. Much better on road and I was able to scrap my plans for a sway bar.

 

[5001craig]

5001,
are you running full width or stock EB rear axle?

Stock width axles. I would seriously think about full width for a lot of reasons. though.

I want to be clear that I am not one of the Wise Ones here on CB. I just read a lot and learn from what others have done. Everything has been done before--it just takes searching for it. The only thing unique about my swaybar is that the other one I saw on Colorado Broncos didn't have to sneak around the upper shock mount I wanted to use (and came with the Duff 4 link kit).

 

[5001craig]

M95 skyjacker shocks took care of my sway issues. Much better on road and I was able to scrap my plans for a sway bar.

I really want to upgrade my shocks. I don't like the way my bumpstops hit when I use them. I had my front tires about 3' off the ground in July at SLSD. The wind peaked the dunes a ton and it was a fine line between too much speed and not enough. So I started looking at good bumpstops (even started a thread here) and pretty much came to the conclusion that I need bypass shocks for what I'm wanting to do. Looking at some King's like their three tube bypass shocks (PR3014-BP3H).

I got everything pretty close on my build as I'm using all but about .25" of the shocks uptravel based on my scientific zip ties both front and rear. I also have Duff's long arms up front. I really like how beefy my front and rear suspension kit is and that's what this thread is about. I do not mean to distract from this thread--the quality of the kit and how beefy it is is amazing. How well designed it is? Others would know better than me but I like mine and I have not even put a line to the wheels. It's been a busy summer.

And Monster Mike was great about answering my stupid questions like how do you put the axle exactly where you want it... It was very cool meeting him, Suzy and Mr. Duff at SLSD at the Bronco Takeover last month.

 

[Monster Mike]

M95 skyjacker shocks took care of my sway issues. Much better on road and I was able to scrap my plans for a sway bar.

That's good info, I'll grab a set and try them on the Bronco we have at the shop. Thanks!

Awesome Info Craig, thanks for chiming in. It was a great time at SLSD. We plan on building a sway bar similar to Craig's design and testing it on all versions of our 4 link.

 

[TruFordBlu]

I didn't want to start a new thread as I found this one that relates to information I'm looking for. I have a question for the guys already running the Duff 3.5 or 5.5 long travel 4 link kit. When completed, was is the distance from the top of the axle tube to the bottom of the frame both front and rear? I'm just working out the math for lift in the suspension alone. My kit is already installed (great stuff by the way), I just want to know if I'm in the same ball park as others. Thanks, David

 

[nvrstuk]

If Steve thinks the Duff 4 link is a good cross between on/off highway then go for it rather than building your own... a lot of time and effort designing (with the advice of others here for technical tips and pro's & con's for all the variables). I know Mike has put a lot of time into designing it!!

I gave up running leaf spring setups with a very durable/dependable anti-wrap bar (3 separate attachment points on the rear housing) that did not limit articulation at all...but I ate leaf springs every few years...ate leaf spring hangers every few years... got old, real old. A well designed 4 link has some advantages for off road but they are EXCELLENT at keeping your pinion pointing where you want it AND zero, I mean zero "wrap" so that is no longer an issue. I tend to have more HP than many and tend to use it often and with 40"s that's a lot of torque applied to the ground...4 links handle it well.

Hope this helps.

 

[bamabaja]

Hey TruFordBlu, just got my 3.5” Duff stuff mounted. If still need info send me PM of exactly where want measurements and I will go to shop. Good luck !

 

[5001craig]

If Steve thinks the Duff 4 link is a good cross between on/off highway then go for it rather than building your own... a lot of time and effort designing (with the advice of others here for technical tips and pro's & con's for all the variables). I know Mike has put a lot of time into designing it!!

I gave up running leaf spring setups with a very durable/dependable anti-wrap bar (3 separate attachment points on the rear housing) that did not limit articulation at all...but I ate leaf springs every few years...ate leaf spring hangers every few years... got old, real old. A well designed 4 link has some advantages for off road but they are EXCELLENT at keeping your pinion pointing where you want it AND zero, I mean zero "wrap" so that is no longer an issue. I tend to have more HP than many and tend to use it often and with 40"s that's a lot of torque applied to the ground...4 links handle it well.

Hope this helps.

EXACTLY why I went with a four link. I didn't know enough to be able to design one that works properly which is why I went with Duff's kit.

I will say that at SC in '18 I packed a guy and his son in the back seat to Bush's Beans. Around an hour drive with switchbacks along the way. I was NOT comfortable on the drive there as the truck was a hand-full. This was strange and I didn't completely know if it was totally the truck or the truck plus the fact that I had a total stranger and his son in the back seat. Plus the fact that I took most every part apart and put it back together by myself. On the way back he and his son rode with his wife in her car and the truck drove like normal. I've packed people that were lighter a few miles to the dunes and then on the dunes and never felt anything like that.

I guess my point is that if you install a four-like that works well with two people in it be a bit cautious when doubling the weight on a drive. Especially in switch-backs like they have in TN.

 

[Yeller]

And for what it’s worth I got to run the numbers on Duff’s kit as it comes out of the box, it’s right on target for what I consider to be a great functioning system, and it FITS within the constraints of the bronco chassis. I’d like to see some better shock geometry but again it fits and functions well. Shock geometry and or tuning would cure most drivability complaints, but for something that more or less bolts on it’s great and will put perform many of the other kits for that other well supported popular belly button thing with a removable top.

 

[bamabaja]

Hey TruFordBlu, let me know if not what u need.

 

[TruFordBlu]

Thanks bamabaja. Perfect, just what I was looking for. I'm at 12.25"front and 10.5" rear with the power train(351w,4R70W,Dana20) in place and the body on, soft top only no hard top. Plus 35" spare on the rear bumper(all Duff bumpers, tube type)So I think I'm in range to what they were shooting for at Duff. Had it on the highway for the first time since install. The ride is great. Much better than the 70's era lift that was on it. Sometimes it feels like it is steering from the rear. Most noted during cornering while accelerating.(45-70 mph) Could this be a characteristic of the Detroit locker? My next task is a full four wheel alignment to make sure I've got everything pointed the right direction and centered correctly. Good luck on your build. I'm interested on what you think when its done.

 

[bamabaja]

Glad to help. I’ll let u know if I ever get done !

 

[chuzie]

Something that would have been helpful when I purchased my kit was information regarding lubrication of the heims. They squeak a lot when contaminated with dust. Don't use any spray type lubes as they will destroy the liner. The mfgr of the heims recommends using motor oil.

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