Topic: Somethin's Outta Whack!

[bryancobb]

Synopsis: 
Replacing trunk floors (right and left) and SM1351 rear x-member cuz' PO ran with rotten exhaust which ate them up.
No evidence of prior collision repair, etc. in this area.
Method:
Remove & replace rear taillight panel with "FORD tooling" one at the same time.  (Done ONLY for best access to work area)
QUESTION:
How can "dim A" be varied so that the slotted holes in the bumper mount reinforcement brackets line up with the same sloted holes in the taillight panel?  This dimension needs to be increased 3/4" for the slots to line up. 
The frame rails are strong and in great shape and have very little vertical flex.  The rear is on jack stands, supported by the body just in front of the rear wheels.  The weight of the rear axle/springs is pulling downward on the frame rails.  When the old parts were removed nothing moved more than 1/16".
Dim B and SM1351 were perfect and the top of SM1351 is flush with the tops of the frame rails. 
The rear valence fits great left/right, but the top edge is 1/2" or so below Ref line 1.
If I force the frame rails downward (I can) so ref line 1 and the top edge of the valence are flush, the bumper bolt holes line up perfectly, BUT there is a big problem.  The two trunk floors are much too low at the joint where they spot weld to the wheelhouses.  Points B and C DO work out better though.
The bumper mount bracket slots, on the ones I removed were "hogged out" downward until there was no material left at all on the lower holes.  You could barely get a socket on the lower 2 bolts because they touched the trunk floors.
I'm a pretty good investigator (I used to be a GA State Trooper).  My Dad was the shop foreman in the Body Shop of the Lincoln/Merc dealer, (I grew up in the body shop and knew what to look for) I could not find anything that indicated the stuff I took off was done anywhere except on the assembly line.

[baflstangobx]

Try putting your jack stands under the rear end housing and let the vehicle weight sit like it is loaded.  I also like to raise the front end to make it sit correctly and set the front stands under the lower control arms.  You may be surprised hoe much twist is in a unitized body.

[bryancobb]

Thanks for your reply!

That's the opposite way from what I need.  If I set the entire body on stands and let the rear HANG, it helps a little.  If I put the stands on the rear axle housing, it pushes UP on things that need to be pushed down.

You are probably right though, I should not be nervous about forcing the frame rails downward to where they need to go.

[thefordshow]

You'll need to start with a datum line and take some measurements. [the info can be found in a shop manual] you'll need to find out if the rail is too high or your 1/4 is too low in relation to the datum line / base line. Not knowing just how much material you removed before replacing sheet metal, but some times it will move if not supported by other sheet metal. support rods/braces tack welded into place can help suspend something and give correct alignment as new panels get welded in. Working off a steel flat deck is the best way to go, but not always possible.

[bryancobb]

This car had NO rust anywhere except where the PO had ran with rotten tailpipes and it ate up the trunk floors and the rear crosspiece.  That's all I removed except for the rear taillight panel for access.

The frame rails were perfect and the galvanizing inside them almost looked new. 

I bought the car in 1978 from the original owner, sold it in 1980, and bought it back from the same guy last Sept.

He says the car was never wet in the 30 yrs he had it.

When I made the last air chisel cuts, freeing up the frame rail/rear crossbrace assembly (its' rear half only, the front half factory welds were not touched) it DID NOT MOVE left/right or up/down.

I just don't get it.  The new rear crossbrace fit in perfect and its' top surface HAS to be flush with the top surfaces of the frame rail flanges.  Everything was just too perfect!

Then when I trial fit the trunk floors in on top of the frame rails and attached the fuel tank as a jig, everything fit perfect,  EXCEPT...
 The dropoffs were 1/2 to 3/4" too short to reach to the bottom of the lower quarter flanges.  Then when I trial fit the rear panel, and the bumper brackets, and the lower valence, it was obvious the rails needed to go down.   This would fix the short dropoff issue and make the bottom edge of the rear crossbrace flush with bottom edge of the rear panel.

I just can't help but think it WAS outta whack before.  I KNOW it didn't move when I cut it apart.   If the car has EVER been wrecked in the rear, there is absolutely NO telltale signs.  I am ASME pressure vessel designer and grew up in my Dad's body shop.  I could spot repairs from a mile.

[thefordshow]

It can only come down to two things, Its moved or the replacment panels aren't correct. You can measure points on the tail light panel that you cut off to the new one. same with the trunk drop off area.

[bryancobb]

I think it has been wrecked.  The rear panel and rear crossbrace was probably replaced, but the trunk floor/dropoffs were not.  The frame rails could have been lifted by the accident and not detected by the body shop that fixed it.

I'm gonna force it down 1/2 with the porta-power, with the rear suspension's weight pulling down, and "button her up."

It has to be correct that way.