Sub frame alignment?

[jlwdvm]

Any good tricks out there to get the front sub on a 1st gen f-body squared up with the rear, setting wheel base, etc?

[paulk68]

this guy makes it look pretty easy


https://www.youtube.com/watch?v=bmrrNXEbPKg

[Spiffav8]

Originally Posted by paulk68

this guy makes it look pretty easy


https://www.youtube.com/watch?v=bmrrNXEbPKg

So easy your WIFE can do it! Yeah....that isn't happening. lol

[Sieg]

Good system........as long as the rear differential is square in the car.

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line.

[jlwdvm]

I took about a week of measuring and tweeking the sub and rear end placement before I welded on my rear end tabs for my Ride Tech 4-link...everything was perfect. Then I decided to drop the front sub to pull the motor to install a Improved Racing oil pan baffle insert, and a few other things that were easier with the sub out. Everything is back together now and it is time to start tweeking again!

[paulk68]

Originally Posted by jlwdvm

I took about a week of measuring and tweeking the sub and rear end placement before I welded on my rear end tabs for my Ride Tech 4-link...everything was perfect. Then I decided to drop the front sub to pull the motor to install a Improved Racing oil pan baffle insert, and a few other things that were easier with the sub out. Everything is back together now and it is time to start tweeking again!

So I am in the same boat. I have the front sub out of the car to paint and install the ridetech suspension and I have not even touched the rear ridetech bolt in 4 link heck i dont even have my rear end yet to weld the bracket too. Wich one should I put in first the rear or get the front as close as i can then do the rear?

[Ron in SoCal]

Originally Posted by Sieg

Good system........as long as the rear differential is square in the car.

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line.

Not sure I'd trust the pinch weld Sieg, but your first point is key as a place to start. Measure the car twelve ways from Sunday and get that rear end centered as perfectly as possible. Then when placing the subframe underneath you get a reference point for a good X dimension from the front lower ball joints to a common reference point in the rear. If using rear shock mounts - or any other location on both sides such as axle tube ends - make sure they're square / centered as well!

The downside to this method is the the car may not be square to begin with, but it should track straight even if the body is a little off kilter.

There's more, but that's a good start.

EDIT: even after all that, I think mine was off by 3/16". Not sure if it was due to the subframe not being square (?), but that was as close as it would get.

[GregWeld]

Originally Posted by Sieg

Good system........as long as the rear differential is square in the car.

The pinch weld is the most accurate reference on these cars and it's not exactly a fine line.

I would agree with this point -- but most of these pinch welds have suffered some serious abuse over the years -- so it's not always a reliable point of reference. I'm seen some pretty jacked up pinch welds (literally!)

[jlwdvm]

If your wheel base is the same on each side, wouldn't the rear end have to be square with the front subframe (since the wheels are attached to it)? The 4 corners made up of the tire patches would be square...right? I have the sub centered side-to-side according the the pinch welds. Currently I have the wheel base within an 1/8" when comparing drivers side to passenger. I am using wheel studs on the rear with the car at ride height and a level placed on 2 studs and then measuring to a stud on the front rotor after doing the same and also making sure the rotor is the same distance from the frame so toe isn't a factor.