Structural sheet metal interchangeability - Calling all experts

[bing98]

Hey all. Hoping someone can give me some direction. Doing rocker repair work on an 01 GP Coupe. Is there anyone on this board or anywhere else for that matter that really knows these cars with regards to the actual W-Body sub-structure? With all the WBodys sold I can't be the only one that's ever run into this quandary


I'm trying to repair my rockers using as many factory parts as possible, but many have been discontinued. I was able to obtain a right rocker reinforcement and that side is almost finished, but the left is no longer available.


I have done a ton of research and what I have found is that even though the GP was redesigned for 04 there are quite a few inner structural pieces that were carried over. I can't confirm because no part numbers are available but the floor pans seem identical. It's fairly common knowledge that the front seats from an 04-08 GP are a direct bolt in to a 97-03. Many of the rails and rear suspension mounts are the same parts. I have confirmed this.


I'm hung up on the inner rocker and the inner rocker reinforcement. The outer rocker on the 04-08 is most definitely different than the 97-03, but the inner 2 components look identical on any GM part site you visit. The problem is the part numbers are different and the compatibility chart for the 04-08 parts doesn't list my car. I have inspected a few last gen GPs and the parts I can see underneath look identical. The inner components are pretty complex pieces so replicating them wouldn't be possible. I also considered buying another right reinforcement and flipping it for use on the left, but that wouldn't be easy.


I also noticed that the Impala and Monte ran from 2000-05. Same WBody as my 01 GP, right? If I look up the 2 pieces on a GM part website I see that the inner rocker and reinforcement on the 2001 Impala is the same from 2000 all the way to 2013 as well as the 06-08 GP(not sure why the 04 & 05 GP isn't included). So if a 2001 Impala is the same WBody as a 2001 GP the parts should fit right?


Maybe someone can speak to the accuracy of the GM parts sites, but I'm sure they aren't 100% accurate. ANy GM parts guys out there?


Given all this I suspect the inner rocker and reinforcements from the later GP or the Impala will work. Even if they are a little different I can tweak them.

 

[bing98]

Hey all. Hoping someone can give me some direction. Doing rocker repair work on an 01 GP Coupe. Is there anyone on this board or anywhere else for that matter that really knows these cars with regards to the actual W-Body sub-structure? With all the WBodys sold I can't be the only one that's ever run into this quandary.


I'm trying to repair my rockers using as many factory parts as possible, but many have been discontinued. I was able to obtain a right rocker reinforcement and that side is almost finished, but the left is no longer available.


I have done a ton of research and what I have found is that even though the GP was redesigned for 04 there are quite a few inner structural pieces that were carried over. I can't confirm because no part numbers are available but the floor pans seem identical. It's fairly common knowledge that the front seats from an 04-08 GP are a direct bolt in to a 97-03. Many of the rails and rear suspension mounts are the same parts. I have confirmed this.


I'm hung up on the inner rocker and the inner rocker reinforcement. The outer rocker on the 04-08 is most definitely different than the 97-03, but the inner 2 components look identical on any GM part site you visit. The problem is the part numbers are different and the compatibility chart for the 04-08 parts doesn't list my car. I have inspected a few last gen GPs and the parts I can see underneath look identical. The inner components are pretty complex pieces so replicating them wouldn't be possible. I also considered buying another right reinforcement and flipping it for use on the left, but that wouldn't be easy.


I also noticed that the Impala and Monte ran from 2000-05. Same WBody as my 01 GP, right? If I look up the 2 pieces on a GM part website I see that the inner rocker and reinforcement on the 2001 Impala is the same from 2000 all the way to 2013 as well as the 06-08 GP(not sure why the 04 & 05 GP isn't included). So if a 2001 Impala is the same WBody as a 2001 GP the parts should fit right?


Maybe someone can speak to the accuracy of the GM parts sites, but I'm sure they aren't 100% accurate. ANy GM parts guys out there?


Given all this I suspect the inner rocker and reinforcements from the later GP or the Impala will work. Even if they are a little different I can tweak them.

 

[gtpvince]

Hi Bing98,
I am doing the exact same rocker repair/replacement work on my 2002 GTP 4-door, and was wondering what you ended up doing for your repair? Did you end up purchasing the 2004 inner rockers, and did they work on your 2001 GP Coupe?

After doing a lot of research, I came to the exact same conclusion as you that the 2004 Grand Prix GM parts, although the part numbers are different, that they look exactly the same on all the GM parts websites when looking at the diagrams. I am thinking about just purchasing the 2004 inner rockers, and the left outer rocker, and seeing if they will work. For the left outer rocker, I am also in the same situation, being that only the right outer rocker is still available.

Any helpful hints would be greatly appreciated! Thanks!

 

[bing98]

Sorry I haven't responded sooner. Been busy. I will add some more later, but suffice it to say that I'm confident that the 2004 inner panels will work. I ended up taking a chance on an 06-07 Monte Carlo Left inner rocker reinforcement. Like the 04 GP the part numbers are different, but they are almost identical. I compared the 06-07 Monte Left reinforcement to the 97-03 Grand Prix right reinforcement that I already had and the two are identical with the exception of some additional inner reinforcement on the Monte panel. This additional reinforcement adds some weight but will not impact the fit.

I tried uploading some pictures, but I don't have permission to do so. It said I have a 57kb quota on pics which is nothing. I have a lot of additional info that might be helpful that I hope to post this evening when I have more time. In the meantime does anyone know how I can increase my pic quota?

 

[bing98]

I think I figured out, although after re-sizing the pictures I can only load one picture.

On the left is the 06-07 Monte Carlo Left Inner Rocker Reinforcement. GM part# 12458992
On the right is the 97-03 Grand Prix Right Inner Rocker Reinforcement. GM part# 19120465

This is a picture of the inside that faces the inner rocker panel. This panel is sandwiched between the inner and outer rocker panels. If you look closely there is an additional reinforcement welded to the inside of the panel. It runs almost the entire length of the Monte Carlo part. On the Grand Prix part the additional reinforcement is only about a foot long. Because this reinforcement is "inside" the panel it does not interfere in any way with the panel mating to the inner rocker panel. It just adds some weight and of course strength.

 

[gtpvince]

Hi Bing98,
Wow! Thanks so much for the quick reply! It looks like you really did a lot of nice restoration work!
Your information and the pic is so helpful. Very impressive! Any additional information you might have would be great!
I am in the process of ordering the 04 GP inner rockers now, but have not received them yet.
My body shop that is doing the work will be very thankful too, and it will help out greatly.

Thanks again! ~ gtpvince

 

[bing98]

Vince,

Sorry it has taking me so long to get you an update I have been wanting to post this for some time to help others that want to restore these cars. I'm hoping you can post some pics of the panels you bought for comparison.

You said you are ordering inner rockers. The above panel. is the Inner Rocker reinforcement seen here



Here are a couple of different angles of the new ones I showed you earlier.





This is the Inner Rocker panel.....

Before

Almost complete. After fabricating come of the pieces. Just have to weld in and epoxy prime....

So, most likely you are going to need the inner rocker, the inner rocker reinforcement and of course the outer rocker panel. The outer rocker panel was originally part of the Uniside which is basically the whole side of the car. That's how the car was originally assembled. The only way to buy just the Rocker Panel itself is from the aftermarket. Here are some part numbers from different aftermarket suppliers that I found for my 2dr.

Rocker Panel Repair

• Rocker Panel(Aftermarket) - 2 Door
  • Sherman
    • Left - 844-03L
    • Right - 844-03R
  • RayBuck
    • Left - 0830-101
    • Right - 0830-102
  • Mill Supply, Inc.
    • Left - 665-97-40-LH
    • Right - 665-97-40-RH
      
      
      

 

[gtpvince]

Hi Bing98, Thanks so much for taking the time to post these additional pics, and the info on the outer rockers, as they provide a great amount of detail of the parts and the repair work! Wow, that's a great job that you did! Currently I am still waiting on my parts to arrive, and am having them delivered directly to the body shop that's doing my work. When my work begins, I will see if I can provide some pics and info of my repair on my 40th Anniv. 2002 Pont GTP 4-door. Thanks again ~ gtpvince.

 

[bing98]

My pleasure Vince. I have wanted to post everything I have learned from this project for a long time now and just haven't found the time. Thanks for the motivation. A long time ago I was lucky enough to find a thread username Lysander put together over at ClubGP. It helped me immensely. I have never done a project like this before so his pics and details were very useful. He did an amazing job on his. I tried finding his old thread, but ClubGp is no more. As luck would have it I stumble upon this thread he put together over at Autobody101.com. Anyone tackling this project should check it out....

1997 Pontiac Grand Prix rocker panel fix - Update, painted! • How to Paint Your Own Car, Auto Body Discussion Forum & Videos • AutoBody101.com

The next thing I should mention about my project has to do with the lower section of the door hinge pillar that intersects with the rocker. I didn't get a good pic of mine before I disassembled it but this pic from Lysnader's post shows what this section should look like before the outer rocker panel is installed.



Here's a pic of my rotted hinge pillar mocked up with my new rocker reinforcement. This should give you a sense of what I'm referring to.





The hinge pillar is 14 gauge steel and quite a complex piece. I tried forming a new one from some 14 gauge sheet and it was impossible with my limited tools. I could have made it in sections and welded them, but it would have take me quite a bit of time. Then I discovered I could purchase the entire hinge pillar for just $120. My time is worth that so I bought the part. It's the whole hinge pillar and the windshield post, but I only need the lower section.



Here's my rotted piece over the new part.

 

[bing98]

Rear Suspension Trailing Arm mount rust issues

The other area of my Grand Prix the has rot issues are the mount points for the rear trailing arms. Here's a decent looking one.....





Here's mine....



In the GM parts guide this part is referred to as the Rear Rail Lower Reinforced....



It's not exactly obvious where this part goes until you start removing parts. It's welded to the rear rail and floor. It covers and reinforces the trailing arm bracket mounting point. This is what it looks like in place. Without the trailing arm mount obviously......





This is what I found underneath mine when I removed it....



The piece with the 3 threaded holes next to the rail is referred to as the Rear Rail Upper Reinforced It is covered by the Rear Rail Lower Reinforced mentioned above. It also includes the thread hole that the rear outer seat belt bolts to. It looks like this....



After some sand blasting, repair work and epoxy primer.....







When I did this repair I didn't realize what the Rear Rail Upper Reinforced was. So I went ahead and blasted the outer and cleaned up the inside as best I could and then primed it. In the GM parts guide pictures it's a pretty small part. I was unsure if it was the part I was looking for. Because the parts counter people aren't always familiar with these intricate parts that probably rarely get replaced they couldn't tell for sure if that's what I needed. The reality was they are really inexpensive so I took a shot and purchased it. Luckily it was the right part. So I'm going to remove mine and replace it with a brand new one. I'm already in there and there's probably only 10-12 spot welds I need to drill out. I would hate to go to all this trouble and just leave that part buried underneath every thing.

The Rear Rail Upper and Lower Reinforced are readily available as they were used on the Chevy Impalas all the way until 2016. Best of all they are super inexpensive. Here are the part numbers...

• Rear Rail Upper Reinforced(Inner trailing arm mount. Thread holes mount bolts to)
  • Left - 20962316 - $22
  • Right - 20962315 - $22
• Rear Rail Lower Reinforced(welded to rail and floor pan. Goes over Rear Rail Upper Reinforced)
  • Left - 20962273 - $39
  • Right - 10406995 - $39

Of course the trailing arms and trailing arm mounts are also very inexpensive and readily available from RockAuto.

If you are going to all the trouble and expense like I am I would highly recommend considering having these parts replaced as well. With the inner rockers removed these parts are very exposed and easy to access.

 

[Supercharged99]

Re: Rear Suspension Trailing Arm mount rust issues

The other area of my Grand Prix the has rot issues are the mount points for the rear trailing arms. Here's a decent looking one.....





Here's mine....



In the GM parts guide this part is referred to as the Rear Rail Lower Reinforced....



It's not exactly obvious where this part goes until you start removing parts. It's welded to the rear rail and floor. It covers and reinforces the trailing arm bracket mounting point. This is what it looks like in place. Without the trailing arm mount obviously......





This is what I found underneath mine when I removed it....



The piece with the 3 threaded holes next to the rail is referred to as the Rear Rail Upper Reinforced It is covered by the Rear Rail Lower Reinforced mentioned above. It also includes the thread hole that the rear outer seat belt bolts to. It looks like this....



After some sand blasting, repair work and epoxy primer.....







When I did this repair I didn't realize what the Rear Rail Upper Reinforced was. So I went ahead and blasted the outer and cleaned up the inside as best I could and then primed it. In the GM parts guide pictures it's a pretty small part. I was unsure if it was the part I was looking for. Because the parts counter people aren't always familiar with these intricate parts that probably rarely get replaced they couldn't tell for sure if that's what I needed. The reality was they are really inexpensive so I took a shot and purchased it. Luckily it was the right part. So I'm going to remove mine and replace it with a brand new one. I'm already in there and there's probably only 10-12 spot welds I need to drill out. I would hate to go to all this trouble and just leave that part buried underneath every thing.

The Rear Rail Upper and Lower Reinforced are readily available as they were used on the Chevy Impalas all the way until 2016. Best of all they are super inexpensive. Here are the part numbers...

• Rear Rail Upper Reinforced(Inner trailing arm mount. Thread holes mount bolts to)
  • Left - 20962316 - $22
  • Right - 20962315 - $22
• Rear Rail Lower Reinforced(welded to rail and floor pan. Goes over Rear Rail Upper Reinforced)
  • Left - 20962273 - $39
  • Right - 10406995 - $39

Of course the trailing arms and trailing arm mounts are also very inexpensive and readily available from RockAuto.

If you are going to all the trouble and expense like I am I would highly recommend considering having these parts replaced as well. With the inner rockers removed these parts are very exposed and easy to access.

Wow!! Awesome post and awesome information. Thank you so much for sharing this information.

 

[bandook]

Dang it, nice work! I'm taking notes. Think this year I'm gonna start tackling the rust. My rockers are shot. But luckily frame rails and strut mounting points are all good. My rear bumper support also looks like Swiss cheese, but I think that's a bolt on part?

 

[GTP Mark]

Dang it, nice work! I'm taking notes. Think this year I'm gonna start tackling the rust. My rockers are shot. But luckily frame rails and strut mounting points are all good. My rear bumper support also looks like Swiss cheese, but I think that's a bolt on part?

It is a bolt on part. Easy to swap.

 

[wowitsfast]

Unless like in my case, a few bolts snapping off due to rot. Super fun

Sent from my SM-N920V using Tapatalk

 

[bing98]

Thanks fellas. I really appreciate the kudos. First time doing this kind of work so i'm taking my time. I'm hoping to do more once the weather warms up here in New England.

I have wanted to post this info for a long time. Aside from Lysander's awesome thread on Autobody101.com that I mentioned earlier I have found nothing helpful so I wanted to try to change that. I'm hoping to post this info over at the WBody forum as well as this applies to all WBody's. It's nice to know there are others out there like myself that like these cars and want to keep'em rolling.

Wowitsfast, I read your build thread. Nice car and nice work. I particularly liked the quarter panel repair. Well done. :th_thumbsup-wink: I have an gray 04 interior as well just awaiting the rocker repairs. I have a turbo from Grand National for it as well. I plan on painting the whole car as well. Probably a slate blue like below with carbon fiber accents....



or



or maybe



Here it is now....



I'm really hoping GTPVince can get us some pics of the GM panels he bought for his project to confirm they are compatible. The rocker reinforcement I bought was from the 06-07 Monte. I suspect the inner rocker and the reinforcements from the Impala all the way to 2016 will work straight up or with minimal mods.

One thing I don't know how I'm going to replace is the rocker panel ground effects mounting brackets.

The panel is symmetrical so I could easily cut and weld a number of partially mangled ones to make one good one. the problem with is that the salvage yards pick the cars up with fork lifts which tends to crush these brackets. Any suggestions?

 

[Daily Driver]

Hi Guys,

I've been around for a while as "burbman" but had to start a new user name because the site wouldn't let me back in. I had a 2002 GTP coupe and now have the same car again but 40th anniversary. I am getting ready to undertake rocker replacement, and I was able to get a set of rockers from Raybuck, but they look like they only go under the door....I have holes just ahead of the rear wheels, what parts are those? Will try to post some pics of what I'm starting with rust wise.

 

[Daily Driver]

I'm hoping I got to this early...this is the driver side rear, the rocker is gone but the inner is still coated and the trailing arm attaching point looks OK.

Passenger side:

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