Unibody Frame Removal

Cutting Out The Old Subframe and Unbolting From Crossmember

Copyright 2008 by Morris Rosenthal All Rights Reserved

The Omni Project

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As soon as I started looking at the rusted out unibody, it was pretty obvious that the crossmember that supports the rack and ties the whole front end of the Dodge together would be a critical component. After cutting out the rusty flooring and and removing the through bolt that held the crossmember to the unibody (when the subframe was still in one piece), it became apparent that the crossmember was in excellent condition. It's formed from a much heavier gauge of steel than the subframe was, and probably a better grade as well. The picture to the right shows the driver side rear crossmember mounting hole, which I'll design the new subframe elements around. You can also see the two driver side brake lines and the emergency brake cable, which made random cutting a bad idea.
The picture to the left is the remnant of unibody subframe that the crossmember was originally mounted under. After 22 years, it was the crossmember that was holding up the subframe element, which was hanging onto the piece extending up to the shock tower by a thread. I saved it in the hopes it will help me a little with the layout of the new subframe, which I'll be constructing from 2" x 3" thin wall steel tubing. You can also see where it was bolted in the crossmember slot , pretty much all the way to the outside, which I'll try to duplicate in my own construction, though it's nice to have wiggle room.
Now I'm including a four video sequence, starting with hacksawing out the old unibody subframe from the floor just behind the driver's seat. I used a hacksaw in part for control, the brake lines run right alongside the subframe, and I knew that one slip with a grinder would have led to new brake lines. Working with rusty old sheet metal components, I find I don't have to saw all the way through if there's no angle bent in the remaining metal to give the joint strength. The vise grips are a handy tool for working the remaining bits of connecting metal to fatigue it so it breaks off cleanly.
The video to the left below shows the piece of subframe being twisted off the front stub frame, and it becomes clearer with every step that these elements were contributing nothing to the structural integrity of the car. The side frame rails are good, the roof posts are intact, so the whole forms a truss, which kept the front of the car from falling off. The final video shows the cross member in profile, so the hole you saw in the photo at the top left is in the surface that appears on edge. While there wasn't much left of the drivers side metal between the frame rail and the hump, or between the engine compartment the back seat, I think we're in decent shape for attachment points.

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