88IROConv

I bought this IROC convertible new and it's been kept in the midwest in a garage that's not temperature or humidity controlled. I decided to check out the undercarriage after 20 years and 18k miles. I drive it about 1k miles a year. I really have my doubts as to whether the rear end was painted at the factory. It just sticks out with that surface rust. Nearby metal that's painted black does have any surface rust on it. It's not as bad as I thought but I'd like to clean it up. I took a shop rag and rubbed on the rear axle and got down to metal. The surface rust just pretty much wipes off. I also noticed the plug on the rear end is leaking.

RITTER

iTrader: (5)

sharp car!!! looks real clean

Yeah I would paint anything that is bare metal with some type of protective paint, that would look good and keep the rust away

wildjeff

iTrader: (1)

These are exactly the photos I need, I’m in the process of removing the undercoating from my car and wanted to know what it supposed to look like.

The wheel wells look black, is that paint or some type of undercoating?

Camaro0605

iTrader: (3)

The floors are clean...

I would POR 15 it. Take a wire brush to the rust, follow their instructions and POR 15 the rusted stuff. The black would real nice under there. Heres POR15 on my rear w/ a $20 chrome cover.

Jproz1167

iTrader: (3)

You should add that picture to the best convertible thread in the "convertible section" I think that one is by far one of the best looking ones I've seen. Very nice car guy.

When my 84 trans am was brand new then at your current mileage yes it's rear axle as well as all parts that are rusty on yours were similiar. So no I don't think GM ever painted the stuff.

88IROConv

Right Front


Right Rear


Left Rear


Left Front


Gatorback Tires

wildjeff

iTrader: (1)

Is there anyway to preserve the natural finish yet prevent rust? Some sort of clear coat or something.

Mikz86TA

iTrader: (4)

Im in the underside re-freshening process. I had to straighten out a few areas of the pinch weld along the sides. The diff looked just like the 1st one on here. I cleaned it with a wirebrush, some purple power and a scraper. Then used some Rustoleum RustConverter black primer. After I get back aroud to it, I have the POR15 chassis paint (yellow can) for it, the k-member and a-arms. I just got finished sandng, self-etch and red perimering, and black SEM black painting the sway bars. The front is a 34mm and the rear is a 23mm. I also refinished the sway brackets entirely. I also had my older GWest brace start peeling the powdercote. So Im in the process of doing it as well. Im going with red on it for some color and to match the Spohn adjuster sleeves. I also pulled and scrubbed the plastic fender liners, scrubbed and refinished the rest of the front underfender wells, along with about 90% of the entire front area.

CDN_87IROC

I am also a fan of clean undercarriage and rear ends

scottmoyer

I know they painted the rear on at least 87s. Here's mine while in the process of removing the undercoating. Everything that's rusty on his car is painted black on mine.

TTA 1387

This what mine looked like after cleaning all the oil off from the rear main leak. Changing to a Walbro fuel pump and putting the HOT wire kit in.

85Iroc-Z

iTrader: (4)

Is there a way to tell if your car came from the factory with undercoating other than by looking at it? What places did the factory apply the undercoating to?

1991Formula350

How do you take off the under spray??? Where do I have to go to have mine cleaned off as I hate that ugly spray on carp the previous owner did to it before he stored it for many years. Andy

okfoz

When looking under one of our cars there are some things to consider.

I just got done redoing my 89 Convertible and here are some of my findings. SInce I did my 87 as well there are other things that I will share to help out any kind of speculation one way or another...

1) the Borg & Warner 9 Bolt rear axel was painted (at least my 87 and my 89 were) The Saginaw 10 Bolt axels were not painted to my knowledge, all of the ones I have ever seen had no paint on them one way or another.

2) Driveshafts were always unpainted, bare steel, or bare Aluminum (if you were fortunate)

3) The Brake calipers were unpainted, the 88+ 1LE & 89 disc brake rears were made from Aluminum... I took a wire wheel attached to a bench grinder and cleaned them up wonderfully. I will post some pix.

4) If you look at the 88 convertible, you will notice some marking paints. Although I am not 100% certain, I will asertain that the reason for the markings were made during the assembly process. When they made the cars one person would put the bolts in and tighten them, I would assume another person would torque them to spec and mark them as being torqued. If you notice they are in the critical areas, the pan hard bar, the Driveshaft attachment points.
The pan hard bar had BLUE paint on the ends (see first pic and my pix)
The Torque arm that goes to the trans mount had a GREEN paint spot
The driveshaft had a GREEN stripe in the center ( it may have been from the torque arm marking)
The axel housing has YELLOW marks at the driveshaft
If you remove your wheels, you should find that one axel shaft is marked with RED the other is marked with GOLD or YELLOW paint.
ON THE B&W axel there is a decal on the rear cover, this indicates the RPO code. There was a small decal as well which resembled a price tag but I am not sure what was on it.
The SPRINGS should each have a decal, in some cases 2 decals. the decals have the RPO and the part number of the spring...
The U bolts that hold the Sway bar appeard not to be painted on my 89, nor did the Sway bar. This was unusual as I thought that my 87 was painted. I did not find a decal on my sway bar BUT I belive it should have had one, I could be wrong.
The backing plates for the brakes were Gold Cadmium plated (they appear goldish with hints of Green & red)
The Emergency brake retainers appeared to be Zinc plated or aluminized, silver colored at any rate
The Brake lines were silver
The spring in the Emergency brake retainers n the calipers appeared to have also been zinc plated OR they were bare metal.
One anomoly I found was that the rear brake slider on my car appeared to have been only cast Iron, some of the reproduction and the replacement parts have been Golden Cadmium plated... I pained mine black.
The BOLTS in about all of the suspension pieces were painted Black OR they were plain steel, the NUTS had a zinc or Aluminum coating. THis included the Pan hard bar bolts & nuts, and the control arm bolts and nuts and the Torque arm bolts & nuts. I believe they were unpainted with plated nuts.
THe front suspension is a hit or miss, I have seen black painted suspension pieces and I have seen bare metal, the Engine cradle has never been painted in my findings. The front sway bar has a decal with the Part number and RPO wraped around it, and both the springs also have a decal with the RPO and part number.

okfoz

Hear are some Before & after pix:

The calipers: I did one at a time so I would remember how they went back together:

The Springs were originally powder coated, I repowder coated them. I made the decals using a Polyester weather resistand tecal with my laser printer. I measured the original decal, measured the fonts, found the correct fonts etc.

The Torque arm originally was powder coated, I also powder coate it as well. To make the mark I took a piece of Foam and a Green Paint marker, I coated the foam until it would apply correctly to some test pieces and then I did it to the arm... The lighting is different so it appears to be brighter than it really is.

okfoz

Some more before & after pix.

The Axel was originally painted black, so I disassembled most of it and then used POR, I wanted to Powdercoat it but it was not practical because of the oils, seals etc. I used POR, primed and then used Chasis black to get the correct sheen of the paint. I wish I would not have primed it after using POR... too late now. I reused the original brake hoses since they were all dated 1989 and appeared to be in really good condition...

The Pan hard bar you can see that originally it had some blue marking paint. Although it looks white ( again due to the flash on the camera) it is also blue on the reconditioned one.

okfoz

There are a few things that will remove underbody spray.

The stuff is more like tar than anything, some of the Orange cleaners will soak into it and then you can brush it off also laquer thinner usually will remove it. I have found that nothing takes it off without some sort of elbow grease and a brush..

JOhn

88IROConv

This would explain what I'm seeing. There's just no way that rear end was painted.

okfoz

I suspect they put a thin layer of paint on the B&W axel because they were being shipped from Australia... Considering they were on a Boat over salt water for 2 weeks I cannot think that it would have been a good idea not to paint them.

John

Jproz1167

iTrader: (3)

I am just curious as to why your undercarriages are not body color? my 82 is black underneath and my dearly departed 84 was red underneath. Maybe this was a norwood/van nuys difference possibly. Or perhaps something they did in the early years.

wildjeff

iTrader: (1)

To remove my undercoating I used a torch to heat it up then scrap it off. There is still a thin film. My next step will be to use a sandblaster. Then repaint. elbow grease is right, its a PITA. I haven’t had much luck with chemicals

My car is an 83 Norwood built firebird. It’s not body color. The space above the gas tank is still the original cream color so luckily I have something to match.

Jproz1167

iTrader: (3)

Mine were both van nuys cars the 82 seems to be black everywhere underneath of it.

Guest

I'll have to look at the two I have now, but I dont remember any of mine being painted and at least 2 of those were Van Nuys cars.

hwcoll95

iTrader: (6)

WOW so that's what they look like,don't think i seen any as clean

Jproz1167

iTrader: (3)

I was just under my black 82 a short while ago and bottom of my radiator support, floor pans .... everything is black and I highly doubt people that owned it before me would have had it done, Only places I see that it's not black is where the paint has peeled off. even where my transmission mount is the frame rails are black.

Camaro0605

iTrader: (3)

Aircraft stripper takes the undercoating off real well. I slopped a good amount on and let it sat, and it just pealed right off. However its gonna most likely take the paint off too.

You can pick it up at autozone.

2tonedmaro89

o wow very nice lookin 'vert

brp88gta

okfoz, how did you reproduce those stickers for the rear end and the springs? my plan for the winter is to detail the undercarrage and i would like to be albe to put those stickers back on.
thanks,
Brian

Guest

Well my 89 is most definitely not painted anything other than the gray primer. I noticed some overspray here and there, but thats about it.

Iroctopless

That's how mine looks too, and it's still factory fresh and clean.

klause83z28

I too am rather curious about this also. I have an early van nuys car and my undercarriage is red (under the grime and road deposits) My axle is also non-painted, which supports the 10 bolt's being non painted and the BW 9 bolts getting light paint.

Mikz86TA

iTrader: (4)

Mine was a VanNuys built car. Its Bright Red. The underside was undercoated and I assume it was factory. But under the floor pans it had started to wear off. Under that is the geayish primer sealer thats applied B4 painting. Like a few pictured on here. There is hints of the original Bright Red paint oversparayed underheath too. Mostly on the outter edges. I recently started to refurbish the under side. Ive started at the wheel wells/liners and the under radiator areas. Im working my way to the rear. But awhile back I had to replace the pinion seal. While doing that I decided to clean the rear axle and re-spray it. 10-bolt. I was using PurplePower to do this. I noticed that the pinion had slung gear oil in the rear portion of the tunnel. This caused the undercoating to start to remove itself. I sprayed the PPower up there too and it started to thin out and remove the undercoating as well. I didnt finish it but it seems to work at getting it off. It seems to soften it up. Its black tarish and messy. But looks so much better IMO without it

Jproz1167

iTrader: (3)

When I did all the 1990 parts conversion on my black 82 T/A ... Anyway I replaced the fuel tank which was the original 82 tank and my cars floor pan was even black up under there so this isn't mearly over spray under my car.
The black tar coating (undercoating) appears in my wheel wells and that appears to be original however that is the only place the car has it. My red 84 which was purchased new by me was a van nuys car which I purchased in Minnesota and it's wheel wells and undercarriage were very simiarly done to my 82's which was originally sold at a pontiac dealership in Ontario California.

I am working on detailing my 82 and will thoroughly clean its wheel wells to show you.

Red92Bird

my 92 bird was bought new by my mom, and looking underneath its primer gray with body coler overspray in places, and has a thin coat of undercoating in each wheel well.. also has the rusty (unpainted) ten bolt and drive shaft.

Mikz86TA

iTrader: (4)

I think the wheelwell undercoating was standard for 2 reasons. 1. it covered the seams and seam-sealer good 2. it made it black and less obtrusive than if it were body color. Can you imagine a JamacaYellow Formula with yellow under the wheelwells.

Jproz1167

iTrader: (3)

I think the wheel well coating is more for noise then anything else.

Guest

To prevent the wheel wells from rusting out, there's a lot of water being thrown around in that area of the car.

I actually brought my other car here to work today. I'll have to take a peek underneath it and see if its painted, I think its not. I wish I could remember if my 84 was painted or not, I dont remember it being painted but its been a while. It may have been more year related than plant related, cost cutting/painting process move at some point in time.

86 Van Nuys car, not painted just primer and overspray.

wicked-irocz

My car is an 89 with 33000 miles

The rear, front suspension/driveline looked just like the vert posted. I cant see them having any paint really from the factory on the rear/a-arms/driveshift. I have the bw rear. The panhard/k member/tq arm/rear control arms were painted but pretty light. The underside is mainly red and it is a red car though it is light and overspray as just inside the pinch welds/ribs on the floor its grey primer still.

wildjeff

iTrader: (1)

On the cars that are not body color are they still painted? I can’t imagine the factory leaving the undercarriage in primer. Primer is not that durable and not water proof. They must be painted; maybe they are all painted the same color to save money?

Mikz86TA

iTrader: (4)

Its more of a PrimerSealer. Its kinda glossy like paint and not thin and dull like Primer

TTOP350

iTrader: (8)

I know this is a old thread but anyone have any more pictures of the bottom. Looking for rear swaybar info if any were painted or not. I haven't seen any painted that I can remember.

GarageToys

iTrader: (6)

I can't help with the swaybar question, but I do have something to contribute to the thread. A bunch of different methods of undercoating removal have been discussed, but on another corner of the internet, I was reading about a guy who just bought a clean 1-owner 1960's car but it had been undercoated when new and he wanted to remove it. Someone suggested dry ice blasting (yes, that's a thing) and he found a place locally that did it and it came out perfect with no damage to the original paint on the floorpans. Basically it freezes the undercoating, you tap on it and it falls right off. Here is a company that manufactures the machinery-- they may have a listing of local shops that do it: https://www.coldjet.com/dry-ice-blas...e-preparation/

TTOP350

iTrader: (8)

We have a cold jet dry ice blaster at work and I have wanted to try undercoating removal with it but that's great info !

jczoka

This is a 400mi 1990 I saw on BAT. Sway bar looks unpainted

chazman

iTrader: (4)

10 bolt rear ends were bare metal and unpainted. BW 9 bolts were painted black, I hear to make the boat ride over from Australia without getting rusted.

TTOP350

iTrader: (8)

Must be a veeeeery early 1990 to have a 9bolt in it.

JT

iTrader: (1)

jczoka's post states 1990 but that's the 1989 Camaro that was recently on BaT that brought a "world record" (?) bidding price.

okfoz

I know that there have been sightings of 1990's with the B&W axle, but there is no 1990 with the RPO for the B&W axle...

jczoka

JT is correct. It's a 1989. My mistake.