Does my car have two right-side lower control arms in the rear?

[BTF/PTM]

So I think I figured out why the car dog-tracks a bit. I got a good look at the suspension while the car was getting new tires put on today. Maybe this is the way it's supposed to be and I need to look elsewhere, but it definitely looks like someone at some point needed to replace the left rear LCA and ended up using an inverted right-side one instead. If those two arms have camber and toe designed into their angles, that would definitely explain why the left side is funky.

image one, the right side with control arm apparently right-side-up

http://s132.photobucket.com/albums/q27/AwwsChwA/z%20parts/?action=view&current=rightLCA.jpg

image two, the left side with what looks like a right-side LCA inverted

http://s132.photobucket.com/albums/q27/AwwsChwA/z%20parts/?action=view&current=leftLCA.jpg

image three, a poor attempt at a full underside view of the two control arms.

http://s132.photobucket.com/albums/q27/AwwsChwA/z%20parts/?action=view&current=bothLCAs.jpg

Am I correct, or is this actually the way the cars were built?

[WW2Winger]

Same part number. The factory used the same control arm for both sides. One is just upside down. You have another problem, not this one. Sorry

[BTF/PTM]

Well, I guess that's good news and bad news. I'll have more opportunities to dig through the suspension tomorrow when I bleed all four brakes.

[mlc240z]

Yup, it's weird but true.

At least you noticed it before disassembly.

Thought the same thing when I refurbed the rear suspension, reassembled driver's side in what looked like the correct position and then tried to reinstall.

Inner contact points way off and had me scratching my head for a while trying to figure out what I screwed up.

[Darrel]

How do you know it doesn't have 2 left side control arms?

[moritz55]

WW2Winger is correct... I observed the same when looking under mine prior to bushing, coils/shocks were being planned to be replaced....and since my steering wheel was always turned slightly to keep the car going straight down the road. I knew it was dog tracking slightly....

I've attached a photo from this website of a New Rebuilt stock 240z. It may help you better understand the suspension.

Here's my rear end rebuild and dog-tracking fix. Read post #77 and beyond as it's my experience on what I did to correct the dog-tracking. My rear end also is much more quite as I'm sure I was dragging the tires:

http://www.classiczcars.com/forums/showthread.php?t=33630&page=4

What I found was that my rear end was twisted such that the driver wheel (-0.01 degree, toe-out) was 3/8 inch further back than the passenger wheel (+0.46 toe-in). After all my work they are now square and my toe-in for both rear wheels is in spec and equal for each rear wheel.... around 0.21 degrees toe-in for each wheel if I recall.

Hope this helps....and good luck.

Edited April 4, 2010 by moritz55

[BTF/PTM]

Thanks, everyone, glad I'm not the only one to think it's weird. Rather than start a new thread, I'll ask here. I've got the car up on Jack stands now, sorta studying the suspension and the service manual. The PO installed a R200, so I'm reasonably certain things got tweeked during reassembly. Hopefully nothing is bent.

All that said, I know from reading the manual that a lot of the bolts need to be torqued under vehicle load and I lack equipment to do that. Is there anyone in southern California who might be willing to help me diagnose and fix the problem correctly? I don't just want to pay a shop to do it, I wanna help and learn from it as well.

My symptoms are similar to other posts, the left rear has a ton of toe in and negative camber and the right rear isn't so bad but it's also off a bit. Definitely gonna scuff away the new tires if I don't get it fixed, and the slight dog track is getting old. Thanks again, everyone.

[moritz55]

It sounds like your vertical braces (the 2 black plates in the photo in my prior post above) which come down from the body and attach to the cross member are bent. Your driver side may be bent forward and your passenger side is bent back causing the rear to be slightly rotated to the right.

Also for the R200 - the mustach bar is reversed such that the space between it and the black vertical braces I referenced is barely 1/4 inch .. maybe a little less. Check this to see how bent they may be.

If you are handy ... drop some plumb lines to your garage floor (plumb line I used was twine with weight on it like such as a fishing 2oz or 3oz sinker). I put tape down on the floor so I can mark the plumb points easily. If you also have a Carpenter Square or Tee Square it will help so you can get some right angles off your plumb marks on the floor from the car body/frame and compare it to your rear transverse link left and right bolt positions. Just be symetrical on where you make your plumb drops off the body - from the same position on right vs left side.

Two good body plumb reference points are the left and right mustach bar bolts since they attach to the body. If you drop them down to the floor... and connect the two points with a line.... Then .. drop two plumb points from the center of the rear bolts on transverse link that attaches to the two vertical braces... connect these two points with a line also ..

Now with these 2 lines... if your rear end was square they should be parallel (have equal distance between them)... if they are not - you can calculate the rotation angle and toe-in differences using the Carpenter Square and simple Trigonometry.

Here's some easy trigonometry info: http://wright.nasa.gov/airplane/trig.html

Here's a sine table: http://wright.nasa.gov/airplane/tablsin.html

Here's a tangent table: http://wright.nasa.gov/airplane/tabltan.html

Hope I didn't make it to complex... but you should be able to diagnose how much out of square your rear end is...

Good luck.....

Edited April 5, 2010 by moritz55

[BTF/PTM]

Thanks!! I'm a mechanical engineer by trade, so the math explanation makes good sense. I'll pick up a square, some chalk and some plumb bob stuff and give it a stab. Never done anything this in depth on a chassis before. I'll keep updates coming.