This is my first 4 link install. and it looks like we may have problems. I have read everywhere and found nothing. so please give me some help here. I attached some photos to show part of what is going wrong. I bought the triangulated off ebay, 4 link differential bracket from fbimini, and a junk yard camaro rear end for my 51 pontiac. Everything is centered good. but for some reason when the airbags are aired down its perfect, then when aired up the bag misaligns. the bottom of the rearend seems to more forward and the top seems to move back. (picture looking from the driver side of the rearend and the hand on a clock. it seems to go from 12 to 1). you can see by the snapped tack welds how far it moves. The rear lays frame. The contitech airbags have alot of lift. it seems ok up to half way but when aired up they look tweaked. The only thing i can think of is where the front D tab mounts are welded. the top differential bracket to the bottom of the rearend measures say 12" and the front link bars top to bottom measure say 8-9". I have not measured yet cause i am still just thinking. but do they need to be the same distance at the rearend and where the D tabs are welded to the frame? I know that i dont have the correct 45 degree angle on the tops. its just how it fit. look at the pictures closely, these are old and were not taken for this post but i can take new ones if needed.
Looks like too much travel for those short links. maybe build a swivel on the saddle for the bags so they can pivot
no, i dont know ride height, here are 2 more pictures. today was the first time i ever drove the car. its been 4 years and it was completely undriveable and stripped when i got it. i dont know where the drive height is yet.also here is a link with more photos, you may see other angles. http://picasaweb.google.com/chopt51
swivel on the rearend? i thought about that. please explain more. the bars are 20 and 24 i think. 20 on top and 24 on the bottom. that is right? http://picasaweb.google.com/chopt51
You need to establish your ride height before you mount the bag brackets. When you know how high you want the car, then you put your brackets on so your bags are straight up and down when driving - i.e, with no kinks/bends etc
Did you set the car at ride height before you installed the 4 bar? When you install a 4link you are supposed to install everything at ride height. What that means is you set the car on stands and bring the rear wheel to ride height. Then you can weld in the axle to set it to ride height then install the 4 bar. From what I understand this is one way to do it. 1. Level car. 2, Install notch 3. Set rear axle to ride height. (need to be be held in place so you can install the 4bar) 4. Install 4 bar and tack in place. 5. free axle so you can check angles and also see your all good. 6. Final Welds on 4bar 7. shock/bag mounts etc Hope that helps explain about the term ride height.
so it has nothing to do with 4 link bars locations? cause i always thought the aired down location of the airbag was important. it should smash flat right? i thought a 4 link had perfect geometry up and down??? so it does not? i thought aired down it would be strait and aired up it would be strait.... if you got a 4 link triangulated tell me how the bags look up and down. thanks for ALL your guys help.
another post. the bottom brackets for the air bags are not welded yet. so if i jack the rear up to "ride" height and weld it there is that all it needs? its a taildragger. what are the pros and the cons of the bag flattening out crooked. http://picasaweb.google.com/chopt51
like others said, make sure you definately align the rear end at ride height (and weld it in to keep everything aligned along the install) and install the bars from there. At ride height also I believe you should: 1) set the pinion angle at ride height to match crank line. 2) if possible align straight bars flat or slightly (1-2 degree) downward. Overall though, I believe that parallel four links with a centering support (like a panhead) is a better solution through range of motion and to better prevent any binding issue. Disclaimer: i've never installed a four link myself, but used to work at a pro-stock drag racing team and listened to our suspension guy talk -scott noteboom
maybe the problem is that the rearend is so high and the frame is so low now. mounting the bars higher on the frame could help.
I was gonne mention that. The bars should be fairly level at your desired "Ride Height" and then go up when you air the car down, and remember it will swing in a slight ark, so when it is down all the way the lower perch will be slightly tipped forward, but you won't drive the car with is all the way down anyway so it's not a big deal. Also it is hard to tell from the pic, but does the upper bar intersect the lower bar where it attaches to the frame, this is important for basic opperation, otherwise it will be in a bind. It sure does look good on the ground, hope you get it all figured out,.
Pics might be deciving, but it looks like the top and bottom links are not parallel to each other. At your desired ride height while driving you should have all 4 links parallel to the ground and parallel to each other. When you air down te pinion should stay on the same plane. With such a wide range of motion you might be better off with a regular 4 link, and panhard bar.
Your need to relocate the bars on the diff. The lowers need a longer bracket, and the uppers are too high. The more they are angled, the faster the rate of change in fwd/back, and pinion angle. If that doesnt make sense, use a piece of string and look and the arc. Ride heighth is prob where the diff would bottom out on orig frame, from the point make bars parallel to ground (or at least close, with uppers maybe like 1 deg drop. That way, 3 in and your on the ground or 2 in up for bumps.
Ok looked again and your ride heighth looks good. The lower bar mounts should look more like your shock mount tabs, and I would move upper bar tabs to housing. You also need to ck your pinion angle...looks like its pointing down. If motor/trans are mounted normal, it should be angled up at least 3 degrees. Where you bags are inflated, ride highth would be super high, and you would NEVER cruise like that
any rotation in the rear, plus the overall swinging action of the rear will cause the bag to misalign. This is common and nothing to worry about. The bag does not need to be absoluetly perfect straight up and down when aired up. From the photo angles youve provided youll look damn near even at ride height. but, if you ride with it at the height youre showing us, you might want to buy a kidney belt. Be more worried about you 4 link angles and pinion angle than what your bags are doing. as long as they are not ripping at the seams and being stretched beyond reasonable, youll be fine
Think of a clock. When the pendulum moves to one side or the other, it also must go up or down. In the case of your rear suspension the rear end must go forward or back as it moves up and down. Set your ride height first. You can't really do anything else without it. The links should be level or a little up in the front at ride height. As far as the bags bottoming out unevenly, the suspension shouldn't rest on the bag when it's down. You need something else for the weight to rest on. I think the best way is with a preset rubber bumper of some kind. Alot of people just let the frame rest of the rear-end, I was always told this will will wind up causing problems but I've never seen any. As long as the weight of the vehicle isn't resting on the bags when it's down, being unevenly aligned won't hurt a thing. Just because I have to say it...MAKE SURE THE BAGS NEVER TOUCH ANYTHING AS THEY MOVE OR THEY WILL FAIL. I hope this is helpfull and I haven't ranted too long.
Do a search and find some pics of other 4 links, it will help alot L http://www.jalopyjournal.com/forum/search.php?searchid=1319281&pp=25
If I remember right, you need to set the upper bars parallel to the lower bars at stock ride height. Then you mount the bags so they follow the arc of the travel of the rear end. In other words, kick the top of the bags out about a 1/2 inch. I think the link bars will bind (or change the pinion angle too drastically) at the lower and higher part of the arc if not set this way. HOWEVER, DONT TAKE WHAT I SAY ON THIS, LOOK IT UP............I did a parallel 4-link on my 35, so Im no reliable source, but I did research both extensivily before putting mine in the 35. Look to mini truck web sites for a definitive answer.......... they have put a ton of research into getting this proper. Also, there will be more than a few here that can reliably answer. Listen to those with experience.
I have to ask, especially with a car as heavy as yours -- what rod ends came with that 4-link kit? They look really tiny and appear to be cast metal instead of machined. Do they have grease nipples (please say no)?
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