rearend out of square...need help!

Hey guys I ran into a little snag and need some professional advice.


I have a parallel 4 link setup on my truck and for some reason my rear end housing is 3/8 of an inch back on one side. When I adjusted the 4 link bars I built a jig to make sure all four bars were they same length. When I mounted them I just assumed everything was square, since my engine x-member is square and the rear 4 link x-member is square to the engine x-member and all four bars are equal in length?


I noticed the tweak when I was setting up my upper coilover mounts and had one side done and moved to the other side and realized the coilover is sitting 3/8 of an inch back? I started measuring and sure enough the pass. side of the rear end housing is 3/8 of an inch back from the center of the lower ball joint?? So apparently something is out of skew somewhere?


My questions are, can I run the truck with the rearend out of square by that much? I would assume not, but Ive never set up a complete frame so Im not entirely sure? Next question, if I adjust my bars to square up the housing, will this cause any trouble in geometry, having one side of the 4 link bars shorther than the other? To me this seems like the best route, but it seems like too easy of a fix. If anybody can lead me in the right direction Id really appreciate it and any help is greatly appreciated. Thanks guys!

 

3/16 in on one side and 3/16 out on the other would keep you close enough for just about anything.

There's a few threads here that discuss a stagared wheel base by design ( read on purpose)

 

You really need to get it square and equal distance when measuring the diagonal, and front to back. This might mean making your 4-bars different length, or cutting the frame apart and fixing it. Its hard to say without pictures. You also dont want to have your coilovers at different angles (front to back), or have them bind when in compression.
I work for exact tolerances when seting up frames, but 1/32" is acceptable in my eyes.

Rob

 

I assume everything is fully welded in?

If it were me, i would find out where I went wrong, and try to fix that area. You may just need to cut loose and re-weld one mount?

You probably could adjust it, and run it, but if you are anything like me this will bug you to no end if it is wrong...

 

If both x-members are square to the frame and the 4-bars are all the same length, then you need to look at the positions of the 4-bar front and rear mounting brackets and where
the mounting holes are on the brackets.

If you drive it out of square then you'll have a crab and premature tire wear.

 

You have no adjustment in your suspension links? I use heim joints when i build a 4 link to make my suspension adjustable.

Yes you can drive it it will go down the road like a happy dog. Sounds like you have either missed a measurement or your frame is out of square a bit, I would remeasure everything again and or get another set of eyes as you have been looking at it too long already and you may miss what you missed the first time again. Then I would adjust everything accordingly.

 

We used to run up to 1" in wheelbase length difference on a roundy round car..on purpose....but I would try to correct it or get it under 1/8"...Or as 31Vickey said 3/16"...I take it your bars are non-adjustable???...You may want to add some hiems for adjustment...Shawn

 

Check for the housing being warped, do you have access to a jig to see if it is square?
If the housing is warped, not only will the brackets be messed up but your wheel bearings might not last long.

 

This is my thought also,,,is there no thought to adjustment? HRP

 

Some of us learn about building it adjustable the hard way. This may be one of those learning experiences.

It is the same with welding, I knew a fella that welded everything solid as he went, it was a lot more work for him to back up and regroupe than if he had tacked everything then welded it up when he was sure it would all work.

 

My 4 link bars are adjustable with poly bushings. I adjusted them last night to correct to placement of the coilover, but I didnt like knowing that my 4 link bars were diferent lengths and wanted to make sure I could run it like that before I welded everything up. Thats why I wanted to check with some guys that actually know what theyre doing.

All my 4 link brackets are fully welded and all my x-members are too. My coilover and watts link mounts are just tacked in place until I can get this tweaked out.

I didnt even consider my housing being warped?? I have read about welding on a housing and it causing it to warped but it completely slipped my mind when considering whats out. Ill have to check that when i get home. If it is warped will a shop straighten it for you?

 

You can straighten it yourself with a torch. First determin which direction it is warped in then go to the opposite side and run puddles until it is pulled back to where you want it. it is actually pretty rare to warp one that much just welding brackets on it. If it is warped that much you will be trashing wheel bearing left and right.

 

Whats the best way to determine if it actually is out of square? I did the old eye ball trick looking down the tube and it looked good. I would think if it was warped 3/8" you would definitely notice.

 

Take the drums off and spin the axles by hand. If you feel abnormal bind or difference side to side you might have a problem.

 

You said you measured off a ball joint. Why do you assume they are perfect? There are shims involved there for front end alignment. Find a place on the frame to measure from first, then check the rear housing for straight. I welded on a rear housing, and warped the hell out of it. PM me for details on how I fixed it.

 

I have fisxtures here for shortening and strightening. But the axle spin trick that was mentioned will ball park you. If you warped it 3/8" you will know right off when trying to turn it by hand. You can also check by pulling and axle and then sliding it back in, if it is warped a ton it is going to be a bitch to go in either direction.

 

My lower control arms arent shimmed, they are bolted straight to the cross member. I measured it off the fronts lower coil over mount also and it read the same distance out

 

Just adjust each side 3/16" and it will be fine assuming the rear end housing is not warped. Not sure what the type of frame it is but I doubt their are too many old frames that were dead-on square from the factory much less after 50 years of service.

 

^ ^ ^ Yeah, what he said!

 

Unless you're running your truck in a Formula 1 race, dial it in so it's square and don't worry about unequal length links.

 

I agree with the 3/16" guys,.... I never have found a perfectly square frame. Most are really close, to be sure. My own thinking is that 3/8" out of square would do some tire wear, , along with a slight "off tracking".

Happy Roddin' 4TTRUK

 

I had a friend that delivered new cars from the plant to showrooms back in late '40's and early '50's. He told me once that in order to get the loaded car-hauler under some of the over-passes in those days that he would let the air out of all 4 tires and ratchet the piss out of the tie-downs. He felt that all the '50-'51 Fords that he delivered had bent or distorted frames because of it.

 

First check your housing. Even if it's straight, work off of your axle centerline. First, install lower 4 link bars and diagonal link or wishbone and adjust as necessary to get your axle centerline perpendicular to you chassis and the housing centered under the car. Then install upper bars, the drivers side (left) first and set your pinion angle. Last, install right (passenger side) upper bar. This bar should be installed initially with no tension (bolts slide in freely, adjust preload as necessary after weighing or test launching). After all this is done hang shocks and adjust ride height. All this is assuming you already know approx. where you want your instant center. Simple.... (grins) good luck and happy motoring!

 

Exactly what I was thinking. Thought that was one of the main advantages of a four link, flexibility...

 

Can I ask what type of chassis ? And set up for what?

As far as I can see or read the OP has plenty of adjustment.

He's concerned about having one side longer than the other.
I don't think that will cause any major issues unless there will be extreme articulation.

Take just about any OEM vehicle and start measuring stuff and you will be surprised at how far out they really are.

 

Me three.

 

I tend to get a little Anal about square and right on when doing chassis building. I would not let 3/8" just slide by. First off I never take diagonal or front to back measurements off any bolt on parts. Several years ago I had this issue show up also. I found it in the rear axle weld on brackets. The 2 brackets were folded differently even though they came as a pair. this made one longer from housing center line to 4 bar mount holes. It also threw off the coil mount holes. Mine was only a 1/4" off. Fortunately I found this problem while in the frame jig and was able to weld up one set of holes and re drill them. Added a spacer for the coil mount and I moved on.
The Wizzard

 

I think we all need to slow down and take a breath here...

BEFORE you re-adjust anything:
1) Measure desired wheelbase back from lower ball joint grease zerks (or kingpins) and mark both sides on the floor. Tape a line across the marks. This should be your rear axle centerline.
2) Plumb bob the lower 4 link frame mount holes to the floor and measure back to the rear axle C/L. Are they the same distance ahead on each side? If YES, THEN check diagonal measurements from the front zerks to the rear axle flanges. To do this, I hang a plumb bob off the back of the drum register right against the axle flange. You don't care what the number is, just that it's the same both ways... Adjust the axle side to side until it Xs out square.
3) If the 4 link brackets are not the same distance from the rear axle C/L, you have to figure out if the problem is at the rear or the front. Remember, we started with the lower front ball joints or kingpins as a reference. The whole idea is to get the car to drive straight...

I'm a little concerned (don't be offended, I don't know you) about how you said one thing was squared to another-to another-to another. Doing it that way can get you into trouble.

(the front suspension MUST be at ride height when doing these measurements. The rear doesn't matter, but the frame should be fairly level.)

 

The front suspension must be in alignment if you are measuring off ball joints. Its better to measure from a frame point to frame point if there is any question about the ball joint placement. King pins should be square to the frame if installed right so measure off them. Be sure to measure diagonal as well as front to back for a true measure of the frame.

joe

 

There is no alignment adjustment on lower ball joints. Using them as a reference means the car will track straight no matter what the body and frame positions.

Sure, starting from the frame centerline is better, but he's already got everything on and welded...