Topic: Trunk pan cracked? Advice required.

[mac1971]

The body on my 429 convert is in very good shape for the age. However, the one weak area is in the trunk beside each wheel well area where the pan has cracked on each side of the car. Looking at it underneath does not show any damage that may have caused the cracks, I am thinking this is strictly age , wear and tear and the fact that it is a convertible with a factory 429 installed? Also, the car has been on air shocks for many years based on my observations and I know this I hard on the rear suspension.

The car will be undergoing a rotisserie restoration, I am thinking the pan should be changed outright? However, the rest of the pan is in good shape. Can this damage be repaired or is this a case of a full pan replacement?

Thoughts? Thanks

[GT500KR]

I have seen a lot of wrecked and rusted mustangs, and I have never seen any damage similar to that in your photos. Without seeing the underside it's hard to tell. My first impression is it's a result of a previous repair attempt of some kind. Possibly replaced the trunk floor inboard of the frame rails.

[GT500KR]

Puzzling.
 Will be interesting to see what you find after media blasting. You might find that they sectioned that RS quarter with a used one complete with the wheelhouse and frame rail. Iv'e seen it before. Keep us posted!

[WT8095]

The cracks appear to be a combination of fatigue & tensile failure. Fatigue would be repeated flexing, and tensile is stretching. Air shocks shift weight from the frame rails to these panels, putting them in tension beyond what they were designed to carry (normal shock loads). Be sure to check the floor in front of the axle, too.

[Smokey 15]

 Depending on the outcome of media blasting, I would look at the option of welding it. A skilled welder/metal finisher can make the repair invisible.

[67gtasanjose]

Depending on the outcome of media blasting, I would look at the option of welding it. A skilled welder/metal finisher can make the repair invisible.

+1

Agreed that duplicating factory spot welds is basically impossible yet duplicating the structural integrity and concealing THAT repair work is more often easier to end up with positive results. I'm sure the shop would get paid more by replacing the floor pan, that could be why they might be considering that route. You seriously need a qualified WELDER and METAL WORKER not just an auto body collision repair guy. Make sure you have the "right guy" for the job.

Choose your options carefully. You'll pay hell fixing a botched job if somebody F%*@'s it all up.

[J_Speegle]

If that is the results of torque - never seen this happen before - I would be VERY concerned about the frame rail and issues there.

If that is the only issue  buy a replacement panel and just section in that area rather than replacing the whole pan, messing with all the factory welds and date code.

Lucky that there is at least a replacement panel available. They didn't make ones for the Cougar when I did my CJ

[midlife]

+1

Agreed that duplicating factory spot welds is basically impossible yet duplicating the structural integrity and concealing THAT repair work is more often easier to end up with positive results. I'm sure the shop would get paid more by replacing the floor pan, that could be why they might be considering that route. You seriously need a qualified WELDER and METAL WORKER not just an auto body collision repair guy. Make sure you have the "right guy" for the job.

Choose your options carefully. You'll pay hell fixing a botched job if somebody F%*@'s it all up.

+2.  My concern about repairing what is there has to do with metal fatigue: something you can't always see but the metal will fail in the future no matter how you repair it.  Once the metal fatigues, it no longer has the structural integrity as intended.

[drummingrocks]

Let us know what you ultimately decide to do.

[67gtasanjose]

If it were me, I would be getting this car on the rotisserie you mentioned (stripped down of course) and media blast the area, paying close attention to fatigue cracks throughout the area in question. I've seen many more fatigue cracks on convertibles (like more than+20!) that cannot be seen at all before a full strip down and media blasting...and this on a car showing NO STRESS CRACKS PRIOR TO BLASTING!

IMHO, This should give your worker a better idea WHAT ALL NEEDS DONE before any final decision is made. Like Jeff, I strongly advocate the partial panel repairs if at all possible or practical. I've seen too many full-panel jobs on the show field that just look horrible, with "no easy way to get it right now".  It isn't too hard to get a car to look really nice as a whole from say 20 feet, but not as easy to get them right when looked at up close and personal. Working with others who have already traveled the road before is a terrific start. I hope you get a good job out of this one.

[Smokey 15]

If it were me, I would be getting this car on the rotisserie you mentioned (stripped down of course) and media blast the area, paying close attention to fatigue cracks throughout the area in question. I've seen many more fatigue cracks on convertibles (like more than+20!) that cannot be seen at all before a full strip down and media blasting...and this on a car showing NO STRESS CRACKS PRIOR TO BLASTING!

IMHO, This should give your worker a better idea WHAT ALL NEEDS DONE before any final decision is made. Like Jeff, I strongly advocate the partial panel repairs if at all possible or practical. I've seen too many full-panel jobs on the show field that just look horrible, with "no easy way to get it right now".  It isn't too hard to get a car to look really nice as a whole from say 20 feet, but not as easy to get them right when looked at up close and personal. Working with others who have already traveled the road before is a terrific start. I hope you get a good job out of this one.

Exactly. No decision should be made until after you see just what you are working/dealing with. Time for a blast!

[Smokey 15]

 I've seen that kind of damage from air shocks before. Back in the day, my cousin bought a "Mod Maverick", a dealer (Jack Keller in Grand Rapids, MI) package that you could add to any V8 Maverick. You had many options, but the all came with a wheel/tire package and air shocks to ensure the rear tires didn't rub the fenders. He was on the highway and hit a little "whooptee". Air shocks went right through the trunk floor!