3 link rear suspension?

Boss Hugg · May 5, 2017

What are your thoughts on a 3 link rear suspension on a crawler?

We've been planning on a four link, but the price is out there. Over $800 piecing it together using rebuildable joints. I'm thinking three link can be done for $200-250.

We're using 2005+ d60 axles for a rear steer system and since those are set up for the same basic idea as an eb front end, I thought they'd work the same on both ends with one radius arm wristed, so to speak.

However, my partner in crime here, my dad, doesn't like the idea of three link in the rear for traction reasons. He says that with one side being the traction link, it'll upset the chassis under torque, since one side will flex and the other is mounted solid. Basically saying it will raise one side of the chassis and get all twisted up and out of shape. We all know that crawling in ugly stuff can require a smooth operation. I see his point, but I'm curious to what degree this might happen. We're not looking at building anything overly powerful for a power plant.

So what do you guys think? I've seen pics of a rig with front radius arm suspension in the rear... how well does it work if you wrist it on the rear.

Sent from my iPhone using Tapatalk

68ford · May 5, 2017

Giant motorsports offers a 3 link like you describe. They use a hyd bump stop on each side to control axle wrap. Hard to explain. The biggest issue is under acceleration you get a lot of torque rise(rear lift). Only thing you can do to help is make the radius arms as long as possibly so the axle has less torque input to the frame.

68ford · May 5, 2017

http://giantmotorsports.com/index.php/product/daily-driver-link-kit/
Hopefully that link is good.

68ford · May 5, 2017

http://giantmotorsports.com/index.php/product/daily-driver-link-kit/
Hopefully that link is good.

Yeller · May 5, 2017

Geometrically the torque loads will have very adverse effects on how it works. IF you can just Boulder crawl on flat ground it will work great but once you point it up hill or it spins (even slowly) the hop will make you wish for a set of leaf springs and parts destruction was impressive. I have built what your describing and it was a flop. Did it as an experiment and didn't take long and we abandoned it for a 4 link. I've built about every design that you've seen out there and I've abandoned all but three basic designs. The best is a triangulated 4 link (in the rear) second is a 3 link with a track bar and 3rd is a 3 link with a wish bone. All of those can be tuned to work exceptionally well. If you'd like to discuss shoot me a PM with your number and I'll be happy to discuss.

5001craig · May 5, 2017

Yeller--we are fortunate that you are here and willing to help us all. Including me. LS motor preference aside. Lol

garberz · May 5, 2017

Yeller said:
Geometrically the torque loads will have very adverse effects on how it works. IF you can just Boulder crawl on flat ground it will work great but once you point it up hill or it spins (even slowly) the hop will make you wish for a set of leaf springs and parts destruction was impressive. I have built what your describing and it was a flop. Did it as an experiment and didn't take long and we abandoned it for a 4 link. I've built about every design that you've seen out there and I've abandoned all but three basic designs. The best is a triangulated 4 link (in the rear) second is a 3 link with a track bar and 3rd is a 3 link with a wish bone. All of those can be tuned to work exceptionally well. If you'd like to discuss shoot me a PM with your number and I'll be happy to discuss.

Adam, You should take Steve up on his offer. He's a wealth of info on this subject.

Mark

pbwcr · May 6, 2017

Yeller said:
Geometrically the torque loads will have very adverse effects on how it works. IF you can just Boulder crawl on flat ground it will work great but once you point it up hill or it spins (even slowly) the hop will make you wish for a set of leaf springs and parts destruction was impressive. I have built what your describing and it was a flop. Did it as an experiment and didn't take long and we abandoned it for a 4 link. I've built about every design that you've seen out there and I've abandoned all but three basic designs. The best is a triangulated 4 link (in the rear) second is a 3 link with a track bar and 3rd is a 3 link with a wish bone. All of those can be tuned to work exceptionally well. If you'd like to discuss shoot me a PM with your number and I'll be happy to discuss.

====
Would you consider a triangulated 3 link to be equal to a triangulated 4 link?
My take is the 3 would be better, especially with the narrow EB frame. Agree anything with a track bar is a undesirable compromise.

Yeller · May 6, 2017

pbwcr said:
====
Would you consider a triangulated 3 link to be equal to a triangulated 4 link?
My take is the 3 would be better, especially with the narrow EB frame. Agree anything with a track bar is a undesirable compromise.

I do not feel it is equal to a 4 link. It doesn't have the stability characteristics that the 4 link has, it wants to pivot around the center point. IMO track bars have their place, especially on more street oriented set ups. Off road they can be tuned to give very desirable effects but suffer at speed off road and that tuning is difficult to impossible in a full bodied truck, to get it right it winds up inside the floor of the bed.

bronconut73 · May 6, 2017

I always heard the triangulated 4 link was best but made running the exhaust a night mare.

My Buddy put a triangulated 4 link with really long arms in a Jeep. The ride was impressive and his axle hop was gone too. But the exhaust had to dump right out in front of the rear tires and even with that compromise the exhaust was still a bitch....but it rode really nice and took abuse well...

Boss Hugg · May 6, 2017

So... how about kill the track bar and use a Watts link.

http://www.partsgeek.com/dd7l4j2-me...Geek+Nextag&fp=pp&utm_term=Mercury+Watts+Link

The center hole mounts on the housing and keeps the axle centered at all times. How bow dah

5001craig · May 6, 2017

bronconut73 said:
I always heard the triangulated 4 link was best but made running the exhaust a night mare.

My Buddy put a triangulated 4 link with really long arms in a Jeep. The ride was impressive and his axle hop was gone too. But the exhaust had to dump right out in front of the rear tires and even with that compromise the exhaust was still a bitch....but it rode really nice and took abuse well...

Fenderwell headers take care of the problems but you have to ditch the front tank if you have one and getting them to dump after the tire is much more difficult than in front.

ahuggins6 said:
So... how about kill the track bar and use a Watts link.

http://www.partsgeek.com/dd7l4j2-me...Geek+Nextag&fp=pp&utm_term=Mercury+Watts+Link

The center hole mounts on the housing and keeps the axle centered at all times. How bow dah

No pun intended but your link didn't work for me.

Yeller · May 6, 2017

Watts links work but are a bandaid and for off road use the cross bar and links needs to be long enough to support the wheel travel, it does feel better at speed (why they put them on mustangs) but does nothing to help stability. And it adds more complex moving parts = more chance for something to fail.

As for exhaust you just have to have the right exhaust guy. I usually hand build them with mandrel bends and tube, saying it can't be done is just not being creative and patient enough. I personally have never not been able to get a full exhaust on everything I've built, some not ideal but we're complete. I've gone so far as to put 15 bends in 3' of 3" tube and it had to be installed in the correct sequence with everything else (including transmission and tcase) for everything to fit but saying it can't be done is not challenging your self.

NGABronco · May 6, 2017

Yeller said:
but saying it can't be done is not challenging your self.

And Yeller has challenged himself....a lot more that once!!!;D;D;D

Yeller · May 6, 2017

Thanks for the pic NGA! I didn't have that one

Digger556 · May 6, 2017

ahuggins6 said:
What are your thoughts on a 3 link rear suspension on a crawler? I'm thinking three link can be done for $200-250.

We're using 2005+ d60 axles for a rear steer system and since those are set up for the same basic idea as an eb front end, I thought they'd work the same on both ends with one radius arm wristed, so to speak.

However, my partner in crime here, my dad, doesn't like the idea of three link in the rear for traction reasons. He says that with one side being the traction link, it'll upset the chassis under torque, since one side will flex and the other is mounted solid. Basically saying it will raise one side of the chassis and get all twisted up and out of shape.

I would avoid what you're proposing. Your dad is right. My buddy ran a wristed arm and forgot to pin it for the street. Almost wrecked the truck when he had to stab the brakes and the truck body-rolled violently to one side, combined with poor steering geometry almost threw the truck into a ditch. You would have similar issues with a wristed rear link. Definitely avoid.

You can do a 3-link/torque arm arrangement, but cost would be the same. (still 4 links total) I've been running this setup on mine for a while now. Driving characteristics are good. Anti-squat was dropped by a factor of 2 vs. leaf springs. I think people get to hung up on A.S., but in this case it was bad with leaf springs and big tires.

I'll agree with Yeller that a track-bar is not ideal for high speed, BUT taking a 92" Bronco to the speeds that require a 4-link is inherently risky. From my perspective, people have bad experience with track-bars, because 1) they are not mounted close enough to horizontal and 2) they mount them too low causing excessive body roll.

Exhaust routing will be harder with any linked suspension, but not impossible. Just don't take it to an exhaust shop. They do not understand how to tuck it properly for a crawler, nor would it be profitable for them due to the time involved. Just by a mandrel bent builder kit and do it yourself. The results will be much better.

Boss Hugg · May 7, 2017

Digger556 said:
I would avoid what you're proposing. Your dad is right. My buddy ran a wristed arm and forgot to pin it for the street. Almost wrecked the truck when he had to stab the brakes and the truck body-rolled violently to one side, combined with poor steering geometry almost threw the truck into a ditch. You would have similar issues with a wristed rear link.

This crawler will most likely end up with a full time gear reduction box, locked front and rear. Definitely not for use on the road.

Sent from my iPhone using Tapatalk

Digger556 · May 7, 2017

ahuggins6 said:
This crawler will most likely end up with a full time gear reduction box, locked front and rear. Definitely not for use on the road.

Torque roll will still be an issue no matter how the vehicle is used.

Yeller · May 7, 2017

Digger556 said:
Torque roll will still be an issue no matter how the vehicle is used.

Yes to a point of makin easy stuff scary

3 link rear suspension?

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