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Coil spring front suspension for my 79 GMC

New Crossmember

I dont trust the stock crossmember for supporting the trans transfer case and the lower link mount. I havent observed any weirdness so far but I dont trust it for the long haul.
I took some measurements and came up with this custom crossmember and used 3x3 .25 angle and 2x3 .25 wall rect tubing.

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Suggestions for the transfer case mount???

I plan to build another crossmember similar to this one. Mount it 10-12 inches further back on the frame and tie the two together. This should be a **** ton stronger than the one stock crossmember.

The only thing I havent figured out yet is the transfer case mount.
I can modify it to fit the tubing. Is it worth the trouble? Should I use a different mount? Someone has to have done this before.

Any suggestions??

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All three of the front links tie to the cross member I built. It is much 3"x6" boxed cromolly tied to the frame with a 12" long plate, frame high and wrapped under the frame. Looks like something off of a tractor. Used a new stock tranny mount. No I do not have pictures.
 
Read through the whole thread and just wanted to subscribe...

BTW on a side note, what welder and saw are you using?
 
x member

I added some more reinforcements to my custom crossmember. Plated the butt welded joints and made outriggers to stiifen up the frame mount portion. Plus I added these cool gussets from Ballistic.

Avery. Im using a Snap On muscle mig 250 and a 14 inch Dewalt chop saw.
Other than that just basic hand and air tools.

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Second X member

Here are some finished pics.
I added another X member about 12 in behind the trans/transfer case crossmember.
The lower link mount is tied to this X member with 1.5 x 1.5 tubing.

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This should add some needed strength to the lower link mount by spreading the load.
The X member mounts to the bottom and sides of the frame with 8 bolts.
It doubles as a skid plate for the 205.

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Odin side view Xmember 618.JPG

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ktmoutfront said:
Not totally. I will try to find the info for setting it up. The lower the link, the higher the roll center. A number of factors need to be looked at. I went from radius arms to a bottom 3 link. It changed a lot. Works great in the dirt. Sucks on the street.
Click to expand...

The roll center on this type of suspension is driven by trackbar location. It can be estimated as being @ the midpoint of the trackbar.

The higher the roll center, the more stable it will feel on sidehills / off camber. A vehicle w/ Cg and roll center at same height will side hill great, but not give much warning before it flops - when it finally does.

I posted here because I have experience w/ this setup. The rear of my Marvzda is just like this front 3 link. Differences are that my track bar (roll center) is intentionally high, and the setup is on the rear not the front. Also, my 1/4 elip springs double as upper link mounts as they are hard (rubber bushing) mounted to the axle.
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Here's a good view of my "single" lower link:
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BTW, good move on reinforcement for the lower link! And the trackbar will put more force on it's brackets than you think it can..!

Marv
 
Thats a great shot of your single lower link!
Dont count on me for a similar pic of my rig....hopefully:doah:

How does this type of suspension act in the rear?
What are the pros and cons?
 
odin said:
How does this type of suspension act in the rear?
What are the pros and cons?
Click to expand...
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This buggy handles great! Although it is not powerful, when you get it moving fast on dirt roads it works fantastic. Probably the biggest advantage is that with the "center" mounted lower link, you never drag outter "lower links" over the rocks compared to a conventional 4 link. Additionally, the lower link protects the driveshaft (d-shaft is above the lower link) and typically gets scraped up first.

Carry a spare lower link at all times. Do frequent inspections on the mounting brackets/joints and maintenance/change out as necessary. With all the force going thru 1 lower link, you can't afford to have it fail.

As a side note, this buggy has been flopped/rolled prolly a dozen times thru 3 seasons of wheelin'. I've had 1 lower link bolt break (5/8" dia) and changed joints (Daystar flex joints) in the lower link twice.

Marv
 
Last edited:
Hey odin,

I just saw your post over on PBB. Wow..! :eek1:

2 things I'd like to add:

- adding "crazy overkill" reinforcement to the single lower link is not a bad idea. Again as I mentioned before, make 2 and carry a spare. For comparison - my Lower link is 2" x .250 wall [ ] tube sleeved by 2.5" x .250 wall [ ] receiver tube. My rig is much lighter than yours.:wink1: You will not fail a "single lower" in pure buckling. The danger is that you bend it by belly-ing the truck down on something and subsequently buckle it next time you stand on the brakes. So you need to make it stout enuf so it don't bend! And if you see a little bend in it - replace it immediately!

- Many people scoff at the "2 uppers/1 lower" design and will never embrace it. Don't try to win anyobody over. I still have people look at my rig and say it won't work. I have even had a few laugh at it. (honest)
The point is that even though this design is not completely optimum as far as strength goes, it can be built and maintained to the point that it can work. And therefore yields some other advantages that I've already mentioned.

Later. You're prolly tired of hearing advice by now... :D

Marv
 
Thats good advice.

Im very happy with this setup.
Its awesome on and offroad.

Ive added alot of reinforcement to the original design...the lower link is now mounted to two crossmembers and is gussetted front and rear.
I inspect it often and it hasnt contacted anything! The paint isnt even scratched off.
My single lower isnt any closer to the ground than the two lowers of a conventional 3 link would have been. I didnt run a conventional 3 link because there is simply no room to put a single upper anywhere near the center of the truck. Oil pan, headers, trans etc are all in the way. Running the link off to the side IMO is not wise ( torque jacking brake dive etc) so I ran it on the bottom.

On a side note there are a few guys on Pirate that are just jerkoffs and ****em if they hate the inverted three link...as you and I know its works and works well.
 
Defiantly an inexperienced question but, I'm considering doing something very similar to my K10, and am curious if theres any reason to not use a solid chunk of rod as the lower link seeing as it will be taking large amounts of force?
 
Magnum97 said:
Defiantly an inexperienced question but, I'm considering doing something very similar to my K10, and am curious if theres any reason to not use a solid chunk of rod as the lower link seeing as it will be taking large amounts of force?
Click to expand...


A solid bar would weigh a ton and probably not be very much stronger than .25 wall 2.0 o.d. DOM tubing that Im using.

From calculations Ive seen it would take 67000 lbs of force to buckle the DOM tubing Im running. With that kind of force Id die in the wreck too.:eek1:
 
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