Ride Tech 4-link install on 69 FIrebird?

[jlwdvm]

I'm in the process of installing my Ride Tech 4-link with coil-overs and Strange 9"in my 69 Firebird project. I have the lower bars mounted. It took a little tugging to the passenger side to get that bar mounted. I am using my jig that I set to 9 1/4" to get the upper bar tabs mounted. I have a plumb line taped to the side of the quarter and hanging through the center of the axle line to get my side-to-side measurements. It is showing that the rear is biased 1/2" to the drivers side at the moment. I can get the rear to move to the passenger side, but it wants to return to the drivers side when I let go. Just wondering if this is normal until the upper bars and shocks are installed? Will this cause the rear suspension to bind? As it sits at the moment, the rear is 8.5" below the frame per the instructions. Any thoughts?

[jlwdvm]

Anyone from Ride Tech listening?

[Classic Nova & Performance]

Joe,

Just give them a call and ask for Bret M. I'm sure he will be able to answer any of your questions.

[marolf101x]

I was following your post on the same subject on Lat-G:
http://www.lateral-g.net/forums/showthread.php4?t=46222

You found the issue. . .aftermarket quarter panels. Even the OE quarters are not on there perfectly square.
So it's difficult to make sure the rear end is in the car square when you are measuring off a known un-square part.

Though offsetting the rear to one side will make the wheels look correct to the quarter panels the rear may not be squared to the rest of the car, which could keep the suspension from working at its optimum.
However, you are only talking 0.25" shift to one side, so the suspension will likely be fine if you weld in the upper tabs then use the upper bars to center the rear (this is pretty common on 1st gen F-Bodies).
If it were off more, and your upper bar lengths were dramatically different once the rear was "pulled" to one side, then I would re-consider just slapping it in there.

To do it correctly you need to locate the center of the vehicle, measure the wheel mount surfaces from that centerline ensuring they are the same, thereby centering the rear to the centerline of the vehicle. Make sure the front wheels are also centered on this line. Then make sure the rear is in there perpendicular to the centerline, thereby ensuring your thrust angle is zero and the car will track straight and true (must measure from a known good frame structure. If you try the front wheels it won't work as they can move around.)

[jlwdvm]

I was thinking of using the locator holes located at various spots on the rear frame and/or body tub to help locate the rear so it will be square to the body-frame...and then get the front subframe located square to the rear using front-to-back wheel base measurements as well as side-to-side measurements. Probably over-thinking things for 1/4", but when I installed the lower bars, the passenger slid right in and I had to pull the drivers side outboard to get it bolted to the rear. Thanks for the info!

[jlwdvm]

Over the weekend I was able to get the front subframe lined up as close as I could to square with the rear frame (less than 1/16" out of square). I measured diagonally from the gage hole in the front sub and the hole in the rear frame rail and also front to back (on the same side) using the same holes. I then ran a plumb line down from the center hole in the front sub engine cradle and also a line down on each side of the rear frame rail to find the center of the rear frame. Then I ran a line down from the center of the yoke on the rear end to see how far off center the rear was....and it was dead on! However, there is 3/4" of difference in the distance from the wheel mounting surface to a line ran down from the quarter panel when comparing the 2 sides (the drivers side tire will be 3/4" closer to the wheel lip than the passenger side). I guess the big thing is that I think I have the front and rear aligned to each other as close as I can get them. Now I have to weld in the upper bar mounts. Any other thoughts?

[jlwdvm]

I measured...and measured again. I have a line on the floor that is 1/2 way between the rear frame rails and a spot marked from the center hole in the front sub. If I run a line from these 2 points, the plumb line from the center of the rear is with in 1/32" of the center line, and the trans output shaft center is within 1/16". Close enough I hope...even though the rear axle yoke is centered in the tunnel and everything else in the drive line is very close, the rear axle still isn't centered in relation to the wheel tubs.

[jlwdvm]

I am in the process of getting the upper arm tabs fitted to the axle tubes by adding metal and grinding to fit. I have the passenger side done and moved to the drivers side last night and found that it was different from the passenger side. I measured the axle tubes and found that the drivers side is 1" shorter than the passenger. When fitting the upper tabs on the driver's side the inner tab is on top of the end of the 3rd member case. Wondering if this is normal....taking into consideration that the 3rd member yoke is centered in the body-trans tunnel for the drive line.

[marolf101x]

Upper Arm Tabs:
So long as you have the front and rear suspension square with each other, and as square as you can get it to the car, the upper bar mounts will fall wherever they fall.
It all depends on what rear end you have. It all looks good from the pics.


Measuring:
What you have determined is exactly what everyone else who ever worked on a 60's vehicle has figured out. . .they were built with HUGE tolerances from the factory.
It is very common for a bone stock F-Body to have different measurements at the quarter panels. They simply didn't care when they only had 7" bias plys to fit under there. Now, have someone cut the quarters off and put on new ones and you never really know where they are going to end up.

Without cutting the quarters off and placing them exactly where you want them in the car, the only thing you can do is get it as close as possible.
If the rear is 0.75" off from WMS to plumb line from quarter, then you can "cheat" it over 0.375" so it's even.

I applaud your efforts to make sure it's all in there as square as can be. However, let's look at this from a real world perspective. . .Say it's my car, and I've measured and done everything you have done. I'm not going to "re-center" the body panels, so I'd put the rear in there and cheat it to one side, keeping it as close to "theoretical" center as I can while still providing ample room for the wheels/tires.

[jlwdvm]

Thanks for the input Britt! I guess I am more concerned with how the car is going to handle at the track than I am of someone noticing that there is a little more room at the fender lip on the passenger side than drivers! As it sits now, the 3rd member yoke is lined up with the center of the rear frame (as measured from the inside of the frame rails) and lined up with the center of the front subframe and trans output shaft...all within 1/16". I have enough room for my 315 tires on the driver's side, it just isn't as much as the passenger side.

[marolf101x]

Well, you are assuming the frame rails are in there perfect. . .which I doubt they are given the "tolerances" back when they were built.
Most importantly is that the front and rear are in there "together". Wherever the body falls is where it's gonna be.

Now, with that said, will you see much performance difference if you move the rear end over a little to help it fit the body? Not likely.
The rear was "slapped" into the 48 Hour car and it seems to do pretty darn well! (I drive that car a lot and do well with it so I have to talk it up when I can!)