Best 4 bar rear susp conversion for 03 DRW? - Dodge Cummins Diesel Forum
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post #1 of 4 (permalink) Old 10-30-2015, 09:49 PM Thread Starter
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Best 4 bar rear susp conversion for 03 DRW?

I love my 03 2wd dually but I hate the ride.
If you have ever rode in the back seat at highway speeds, you will know that it is almost untolerabel.
My fix so far is the addition of airbags and removal of helper springs, leaf spring spacers, and a leaf of the bottom of the main leaf stack. My intentions were to give the truck a lower stance and softer ride when not towing then air up the bags when towing. This idea was only moderately sucessful. The problem is that there is not a big enough cavity for the airbag to sit between the frame rail and axle. The airbag is also the bump stop now so if ride height is set too low, bottoming occurs and ride is much, much worse. When air pressure is just right for the load , it is not too bad but the truck still has too much rake which take even more weight off rear wheels and make ride quality worse. I understand that the Sprung to unsprung weight ratio is really bad with steel wheels and a very heavy rear axle which ultimately limits how good the potential ride quality can be but I feel i must try to do something. Any ideas? Ride Tech makes a universal kit witch means it fits nothing. I am capable of designing and fabbing almost anything but I'd rather not reinvent the wheel if this problem has already been solved.

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post #2 of 4 (permalink) Old 11-01-2015, 05:59 PM
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You can also check out the Kelderman air ride system with full 4 link. Several people who tow/haul heavy have installed this and found that it gave what they wanted.

Having said that a true 4 link can really help but can also be a real PIA if not built or adjusted properly. If not properly adjusted they can be miserable to drive. 4 lonks can bind easily. Adjusted properly traction can be awesome Or lost.

There are some things to consider, will it be a triangulated or parallel system? Will you run a panhard bar or Watts link? Desired ride height? Single or dual coil over? Progressive coils? Air suspension? Anti-dive? Anti-squat? Roll center? Instant center? Pinion angel? Heims, bushings or mix? Poly or solid bushing?

How much weight will you haul/tow? Driving style will have a huge influence on the adjustments and design.

I don't think you will be able to buy a complete turn-key system that requires no adjustment or setup. Just not the nature of a 4 link. If it doesn't weld in I wouldn't run it. If it can't be adjusted it will always be a comprimise. You may well need to ajust for empty vs loaded conditions.

I have no idea what your abilties are but there are many things to consider if you fab your own. Some use DOM I prefer 4130 seamless tube. I avoid Heims and like a mix of poly/rubber/solid bushings. I use adjustable ends on at least the upper bars. Prefer Watts link over panhard bar. I GTAW everything unless it is it just a bracket I might GMAW. Never SMAW.

Try some of the off road forums. Those guys have done amazing things.

2006 3500 QC Laramie, 4WD, DWR, LWB, G56, American Force 19.5's w/ XDS2 drives and XZE steers, Flowmaster cat back, Pacbrake, ARB compressor, custom fuel filter setup, Superhitch Magnum 30k.
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post #3 of 4 (permalink) Old 11-02-2015, 12:08 AM Thread Starter
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Originally Posted by Mopar. View Post
You can also check out the Kelderman air ride system with full 4 link. Several people who tow/haul heavy have installed this and found that it gave what they wanted.

Having said that a true 4 link can really help but can also be a real PIA if not built or adjusted properly. If not properly adjusted they can be miserable to drive. 4 lonks can bind easily. Adjusted properly traction can be awesome Or lost.

There are some things to consider, will it be a triangulated or parallel system? Will you run a panhard bar or Watts link? Desired ride height? Single or dual coil over? Progressive coils? Air suspension? Anti-dive? Anti-squat? Roll center? Instant center? Pinion angel? Heims, bushings or mix? Poly or solid bushing?

How much weight will you haul/tow? Driving style will have a huge influence on the adjustments and design. /

I don't think you will be able to buy a complete turn-key system that requires no adjustment or setup. Just not the nature of a 4 link. If it doesn't weld in I wouldn't run it. If it can't be adjusted it will always be a comprimise. You may well need to ajust for empty vs loaded conditions.

I have no idea what your abilties are but there are many things to consider if you fab your own. Some use DOM I prefer 4130 seamless tube. I avoid Heims and like a mix of poly/rubber/solid bushings. I use adjustable ends on at least the upper bars. Prefer Watts link over panhard bar. I GTAW everything unless it is it just a bracket I might GMAW. Never SMAW.

Try some of the off road forums. Those guys have done amazing things.
I haul about 8500 lbs when we go racing. Car and trailer weigh about 7000 plus some stuff in the bed. I would prefer parallel four link with a watts link and air bag spring. i would like to truck to sit level which means rear needs to be lower. Obviously Dodge engineering set the rear high so when there is a lot of weight in the truck is level. With the loading that I described with the factory leaf springs, the helper stack would be about a 1/4" from touching and you would really feel it when they would engage. Basically it was an awkward size load for the factory set-up. Another 1500lbs might of made all the difference in the world. I agree with everything that you say about best construction techniques. I was thinking poly bushings and 4130 tubing GTAW welded for minimal noise and maintenance.
We built a streamliner from scratch (carbinitelsr.com) so I'm pretty sure we can handle building a workable four bar set-up but like I said, trying not to reinvent the wheel. Ultimately, it would be good to have both height adjustment (easily accomplished using air bags) but also spring rate adjustment (not so easy with air bags).
Kellerman system seem ok but a bit expensive as there is a lot parts I would not use if i was welding most of it in. Maybe Ride Techs universal kit since I'm welding it in anyways. It has a few issues as the brackets for the reared are only 180 degree engagement around the axle tube leading to warping the axle housing when welding the bracket to axle but I have ideas overcome these issues.
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post #4 of 4 (permalink) Old 11-02-2015, 11:06 AM
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I know exactly what you are saying about 7000 pound trailer and little or nothing in the bed. Rough at best. Make the trailer 10k and put 3 or 4k in the truck it is sweet. Truck camper runs around 5k so it clearly gets all the springs working and is actually a decent ride.

Though I've never used them a lot of people with campers or 5th wheels swear by Stableloads. Helps engage the spring. Many people fab their own. Easy to do. Just lower the bumper with some box tube. Cheap easy try. No harm or foul if it doesn't suit you. It will still be harsh when unloaded.

What are you running for shocks? I know many from the camper forums have found that good or custom shocks can really help in all conditions. Call Don Thuren and ask about a set of custon King shocks. I've not done them yet but it is in the plan when the $ is there.

It sounds like you have a handle on proper fabrication and material. Perhaps a generic kit with a little custom work can fit the bill. I agree that a parallel 4 bar with Watts is the best way to go. At least it gives the best chance for great results and offer good adjustment if (when) needed.

If you go with an air bag system look at putting surge tanks on each bag. It can really help with the ride as it gives a lot more reservoir. Of course the bags should be seperate and not plumbed together. Many people T them togther and wonder why the don't work well.

I'm no expert on this stuff but out of necessity and a poor result from a suspension I had built on a pro-touring car had to learn a lot about suspension geometry. Should have done it ourself in the first place but it all seemed so complex. Now, not so much.

2006 3500 QC Laramie, 4WD, DWR, LWB, G56, American Force 19.5's w/ XDS2 drives and XZE steers, Flowmaster cat back, Pacbrake, ARB compressor, custom fuel filter setup, Superhitch Magnum 30k.
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