Hello all,

Please let me know if this is in the wrong section as it is my first post here on the forum.

After rebuilding my Fiero and driving it for almost 2 years i have decided to take it off the road to give it the proper attention that it needs. upon inspection and removal of the upper rear clip i have found that the passenger side rear upper frame rail has rotted away. i have removed the rail for closer examination and was happy to find that the rot is isolated to only the frame rail, not anything else in the vicinity. i have read up on a few forum posts on guides on making frame rails but want to know if anyone makes these frame rails as of October 2025? i would rather have someone who has experience making them build it and buying it from them before i go trying to making one. this rail is the only rust on the car besides the battery tray and i want to get this fixed before i go forward with my swap.

Any names or leads on anyone who may have info on these frame rails would be appreciated.

Thanks

Rusted upper frame rails are a common issue with Fieros. They can be repaired with some 1 x 3 square steel stock. a bit of cutting , fitting and some basic welding. A while back a member here posted exact measurements and plans on how to build and replace those rails. That build thread is somewhere in the archives and I'll try to find it. If they are not rusted entirely away you may be able to use some steel patches. If this is the only thing wrong with your Fiero it will pay to rebuild.replace those rails.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

there are lots of parts cars in the south with perfect frame rails.if you are a good welder.

quote Originally posted by richard in nc: there are lots of parts cars in the south with perfect frame rails.if you are a good welder.

This is what I would suggest, and recommend highly.
Drill out the spot welds on the rusty frame rails on your car and the donor car .
Weld the good frame rails on your car using the spot welds holes on the donor rails.

Pontiac designed the rear of the car to crush during an accident, and the metal gage, spot weld locations and dimples in the metal rails are all part of the design.

Replacing the frame rails with square tubing does not duplicate the crush engineered design, and in the event of the car being rear-ended, could turn the square tubing into deadly spears going through the passenger compartment rear panel.

I have repaired a few Fieros in the manner I described above. It's a lot of work, but it is a safely engineered repair that duplicates the original design perfectly and is safe.

quote Originally posted by olejoedad: This is what I would suggest, and recommend highly. Drill out the spot welds on the rusty frame rails on your car and the donor car . Weld the good frame rails on your car using the spot welds holes on the donor rails. Pontiac designed the rear of the car to crush during an accident, and the metal gage, spot weld locations and dimples in the metal rails are all part of the design. Replacing the frame rails with square tubing does not duplicate the crush engineered design, and in the event of the car being rear-ended, could turn the square tubing into deadly spears going through the passenger compartment rear panel. I have repaired a few Fieros in the manner I described above. It's a lot of work, but it is a safely engineered repair that duplicates the original design perfectly and is safe.

I hadn't considered that... that's a really good point (about where the spot-welds are, etc.).

There is a diagram in this post that shows the dimensions and angles of the frame rails. More work but precise.
Fiero Frame Rail Diagram

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "