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Old 12-03-2017, 11:40 PM   #1
stick70
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Default Rear End Alignment with 4 Link Install

Looking for some advice from someone who has done this before hopefully. I've got all my bars lined up and everything square. The rear end is centered front to back in the wheel opening and side to side with the frame rails. However...with the wheels installed the drivers side wheel sticks is a good 1/2" closer to the fender well than the passengers. I'll say again, it's dead nuts on measuring from the frame rails. I'm measuring from the wheel mounting surface of the axle to the outside of the frame rail.

So what's best? My gut tells me that I should get it straight off of the frame rails and just flare the driver's arch to match the passengers, but is a 1/4" shift off center really going to jack up the tracking of the car? That's all it needs to be centered in the arches. I'm not going to be running a panhard rod, so I need to get it right now.

Background: 1966 220, P1800 rear, triangulated 4-link install.

Thanks.
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Old 12-04-2017, 11:40 AM   #2
Wagonoff240
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I’m no expert, but wouldn’t it make sense to measure alignment off of the centerline of the car and not the frame rails? I’m doing a build on my 77 280z and have to use the FSM’s geometry to assure my suspension mounts are back where they should be...
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Old 12-04-2017, 12:18 PM   #3
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That's what I'm unsure of. Everything I'm reading says go off the frame, which I did. But I'm pretty sure everything I'm reading is for body on chassis cars, and this is a unibody. Not sure if that changes anything apart from giving me no room for body adjustment. As far as suspension mountings are concerned I'm not using much of the factory stuff so I can put it where I want really. I just want to make sure the car tracks straight.
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Old 12-04-2017, 12:34 PM   #4
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I would draw a line between the center of the front control arm pivots and the center of the rear trailing arm pivots and have the centerline of the axle intersect with that.
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Old 12-04-2017, 01:07 PM   #5
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That makes sense. I'll draw it up tonight and see where it ends up. I haven't cut the factory trailing arm mounts off yet so I'll go off of them.
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Old 12-04-2017, 01:26 PM   #6
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That makes sense. I'll draw it up tonight and see where it ends up. I haven't cut the factory trailing arm mounts off yet so I'll go off of them.
for the rear axle i would measure hub to hub and take the center. Plumb bob everything.
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Old 12-04-2017, 01:36 PM   #7
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Thanks yeah that was my plan. The chassis is set on jack stands level so it's not going anywhere. The hubs are true from the machining after redrill so they're clean to measure from.
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Old 12-04-2017, 02:04 PM   #8
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[QUOTE=stick70;5714932]That's what I'm unsure of. Everything I'm reading says go off the frame, which I did. But I'm pretty sure everything I'm reading is for body on chassis cars, and this is a unibody.

Measure from centerline, the unibody should have a technical dimensions chart in the FSM (factory service manual) that is used to check alignment after wrecks. I am speaking only from my current experience with my other project. Idk if anybody on here has a FSM for your chassis but that’s where I would start. It would have all the proper measuring points and show you how to check for square on each part of the car.
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Old 12-04-2017, 02:33 PM   #9
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Thanks I'll look into that as well. I have a green book here, it has centerfolds in the back with all of the frame dimensions. I imagine normally it would just be aligned in the wheel arches with the panhard rod, but since I'm installing a totally new system I'm trying to make sure it's in there as good as I can get it.
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Old 12-04-2017, 03:57 PM   #10
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Thanks I'll look into that as well. I have a green book here, it has centerfolds in the back with all of the frame dimensions. I imagine normally it would just be aligned in the wheel arches with the panhard rod, but since I'm installing a totally new system I'm trying to make sure it's in there as good as I can get it.
Using the body floor control drawing from the service manual was going to be my suggestion. If, according to the drawing the original suspension attachment points are centered and the frame rails are centered then centering the rear axle with respect to the frame rails would seem appropriate. Having nice clean undented frame rails will facilitate the measurement.

I have a 140, not a 220 so my experience may not apply. Out of curiosity I was able to find the front pivot points for the trailing arms easily on the vertical profile of the control drawing. Finding the pivot points in the horizontal plan, not so easy. I think I found the flanges for the pivot point which suggests that they are centered; but, they are not so obvious because they appear to line up with floor pan extrusions so I would have to do a visual check to confirm.

After putting in shorter springs I had to adjust my panhard rod to re center the back axle. I initially tried measuring from the disc face to the inside lip of the wheel arches. I found a lot of variability in the wheel arches in my car so settled on adjusting the pan hard rod to give equal distance from both disc faces to the inside of the accompanying rail / body extrusion that arches over the back axle.
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Old 12-04-2017, 04:15 PM   #11
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Find the center of the front crossmember and pull a string back down the center to get the side to side right.

You might also measure diagonally from that front point to a point on the rear axle housing out at the bearing to make sure it is square.
Body's are notoriously different side to side I would not trust a wheel opening for anything more than keeping the water thrown up by the tires under the car.
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Old 12-05-2017, 12:51 AM   #12
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Spent a fair amount of time mapping it out on the floor tonight. The chassis is square from the trailing arm mounts from the front of the car and the back. That's good news because I know it's been hit in the rear, I'm just now finishing up the quarter panels from that. One funny thing is that while the diagonal measurements all match the book, the frame rail spacing is an inch too wide in front and back based on what the book says. It's the same everywhere so I'm going to say it was made that way.

I found chassis centerline as was suggested above and found that the axle could stand to go 3/16" to the passenger side to line up on center. The center of the axle was found off of the hubs. That will help the situation, but it's still looking like I'll have to do a little bit of fender flaring on the driver's to make it all even. I'm not super surprised that the wheel wells are uneven a little side to side really as Rick said.

Anyways thanks for the advice guys, I'll try and get it in final position tomorrow so I can weld it up.
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