Setting drive line angles properly for 4link

I kind of disagree with you guys a bit on this. If the 4 link is set up right, you can build it when its laid out and have no problems with the pinion angle or anything else. You want the distance between the upper and lower bars to be closer on the frame than it is on the axle. You want to make it so the point where the upper and lower bars intersect(called the instant center) around the front bumper. Download this program, you can put in all the measurements of your suspension and it will tell you how your 4 link will work. Also if you havent already, I would suggest getting a copy of Chassis Engineering by Herb Adams. Lots of good info about this subject in there.

When we set up rear link systems it is always layed out. We never set them up at ride height. I have one question and that is are you doing a straight four link w/ a panhard bar or a triangulated link system? I would think that you are doing a triangulated link system.

Bag on bar lift with triangulated upper bars

Thanks for all the input guys i am looking forwarding to getting this setup this weekend

The airridetalk links someone posted above are about as good as it gets explaining u-joints and pinion angles. Read that over... twice.

Another good read for this kind of stuff is Chassis Engineering by Herb Adams (It's under $20 at chapters. Get it. It's awesome.). It will explain all your instant center, what changes will affect things elsewhere in your suspension/steering, etc.

As I said you said earlier you will want to set up your links with the truck laid out for a few reasons (1) if you set the bags/links up at ride height your bags might lay crooked when fully layed out (2) set your pinion angle approx. 5 degrees above zero because with triangulated or three links your rear end will track downward to a point and by correcting for this when layed out your ride height pinion angle will be zero not creating any vibration or kinks (3) and the only links that do not change pinion will be your parallel link bars that run a panhard bars. I hope this helps with pros and cons of setting up your system when layed out.

Setting it up layed out is making much more sense especially when it would come to setting up the bags/bars. I have learned alot from the past few posts and its starting to make more sense to me. As useful as it may seams I do not think i will be able to understand how to use that program properly.

I used that program, and once you figure it out, it makes setting up the link waaaay easier.... even though you already have specific bar lengths it will deff hep you with the correct placement of them. id give it a shot and try to understand it....if you have any questions you can ask me... ive played with the program for a while now and understand it pretty well

Yeah its really not as complicated as it looks. I can try and help you out too if you want.

today i tried to get the chassis engineering book but had to order it so it will be about 2 weeks.


In order to get the suspension setup when layed out i will have to burn the notch in before hand.

are these correct? if not what should they be?

Wheelbase 104.0 in
Tire Diameter 36.00 in
Tire Rolling Radius 17.00 in
Vehicle CG Height 25.94 in
Vehicle Mass 5,000 lb
Front Unsprung Mass 800 lb
Rear Unsprung Mass 700 lb

i dont understand any of this either

Upper Links x y z
Frame End 30.00 20.00 25.00 in
Axle End 0.00 10.00 30.00 in
Lower Links x y z
Frame End 50.00 5.00 15.00 in
Axle End 3.00 20.00 15.00 in

My lift links are 26" and my triangulated links are 28.5" when adjusted to shortest length. Honestly there is no way i am going to be able to use this program by filling it out myself. If you guys could give me a hand with this it would be apreciated.

How can i ensure the truck will lay out evenly with both tires tucking the same amount? lay the front out and then block the rear of the frame under the cab the same height as the frame under the front of the cab? so the frame is level? How would you suggest to ensure the tires tuck/the truck lays out evenly? These may sounds like stupid questions but i want to do this right the first time. Please keep in mind i have NEVER done this before.

hey man im not home right now where i have the program but when i do ill do my best to get you the nmbers you need