Mods, Tips, and Experiences

updated July 11, 2005

 

I will be listing some low-key mods and tips that I used to make my GNX a little more personal, yet stock appearing and always reversible with no trace.

IMPORTANT- The GNX was subject to the same Powermaster brake switch recall as the 86/87 Grand Nationals. Since most owners kept their GNX original, it is very likely your GNX didn't get the new brake switch. DO NOT drive your GNX until you get the proper GRAY brake switch, either from the dealer or on the open market. The original (black) switch will crack, spray brake fluid all over your motor, and oh yeah, you won't be able to stop the car.

Get this fixed!

BOOST GAUGE- The stock boost gauge doesn't really make sense for the car (30hg-15psi). Thanks to the simple construction of the IP, it's a 1 hour operation to replace it with an Autometer or any other 2-1/4" mechanical boost/vacuum gauge. If you want to get crazy, the Autometer 2614 goes to 30psi with vacuuum to 30Hg. Check below regarding the "speedo cable lube" for a procedure to access the IP gauges.

SPEEDO CABLE- The GNX uses a specific upper speedo cable (12332813) and it's not available anymore. When yours starts to squeak, here's my procedure for How to Lube the Upper Speedo Cable. Below is a picture of what it looks like opened:

GNX Speedometer Cable

The lower speedo cable is the same as stock so you can buy a new one. The problem is you have to run it exactly like ASC did to reach the trans properly. This may be difficult because of the work they did around the fenderwell. Not to mention the old one may have to be cut to remove it.

STEERING COLUMN- Since ASC had to lower the steering column to install the IP gauge panel, sometimes the steering column isn't lined up exactly on center. Follow the appropriate section of the speedo cable lube procedure to straighten yours out.  

ALARM LED- While you're in the IP, consider snaking your alarm LED into the idiot light cluster to replace the "Security" lamp. I unplugged the worthless factory alarm so the lamp wasn't being used anyway. The LED shows fine through the bezel. Same can be done with your detonation detector LED. Here's a pic:

Alarm LED wired into the "Security" lamp position

FUEL GAUGE- My fuel gauge is a little jumpy when the fuel is sloshing around. Anybody else notice this? I'm sure it can be cured but I'm too lazy to experiment with a capacitor value.

TIRES- Like many owners, I don't drive mine more than 3000 miles per year. This is an opportunity to use a high-wear, no-compromise road racing tire like a Yokohama A032R. They are pretty sticky, have more tread than drag radials, look VERY mean, and most important- they are Z-rated so they HANDLE! The drawbacks are that they are LOUD at 45mph and just like slicks they throw gravel. I'm looking for some magnetic quarter guards. They are NOT a substitute for drag radials at the track.

While not a drag radial, the Yokohama A032R is a very sticky Z-rated tire.

WHEEL BALANCING- My wheels have tape weights on them. They can be used for dynamic balancing and cause less damage and corrosion than conventional "bash-on" weights. I also added chrome valve stem covers.  

CENTERCAPS- Kirban markets reproduction centercaps for GNX wheels, but BEWARE, they are all plastic and the "fingers" melt.  My fronts fell off repeatedly... Now I use a Firebird GTA hub (12514403) and medallion (10052353) available from any GM dealer and the GNX decal (#1510) from Kirban. The GM hub has metal "fingers" which hold very strongly. This is actually the way that ASC constructed the original GNX center caps, so I call it 99% original.

BRAKES DRUMS- The GNX uses  aluminum brake drums. When the time comes to replace them, you will likely have trouble finding GM aluminum replacements. If you have access to a pick-n-pull junkyard, here is a list of cars that also use aluminum drums (this information is from a GNTTYPE post and I take no responsibility for it):

83-84 Blazer/Jimmy S/T models , 80-84 Buick LeSabre 85 RWD , 78-81 Buick Century , 78-87 Buick Regal , 81-85 Buick Riviera , 82-92 Chevy Camaro

86-89 Chev Full Size passenger cars , 78-81 Chev Malibu , 78-88 Chevy Monte Carlo , 82-84 Chevy S10/S15 , 80-85 Olds Delta 88 , 78-82 Olds Cutlass

80-81 Pont Bonneville , 83-85 Pont Bonneville , 86 Pont Parisienne , 82-92 Pont Firebird , 78-85 Pont LeMans , 78-88 GMC Sptint/El Camino

The post states the drums are 9.5" x 2" and recommends you measure the steel liner because it can't take much cutting. If you can confirm or deny this info, let me know.

EXHAUST- I had a tough time finding a replacement exhaust that cleared the rear suspension. I only know of ATR and Kirban making a GNX -specific system, both 2-1/2" duals and around $600. ATR's is stainless all the way and Kirban's is only stainless in the muffs (which are ATR muffs!). I have ATR's system- it's louder than the Ultra Flows on my GN, the clamps crushed too easily and fit was not "perfect". A custom stainless system with Ultra Flows would have cost double though, so the ATR seems like the only game in town.

TURBO/INTERCOOLER- I promptly removed my stock turbo and replaced it with a TA49. I also replaced the intercooler with a (manufacturer's name withheld) stock-appearing unit and faux intercooler sticker by Buick From Hell (who makes excellent custom pieces). Those GNX -specific parts are sealed and tucked away.

NOTE- if you are in the market for a stock-appearing intercooler, please research the manufacturer's customer service practices on one of the Buick boards. 'Nuff said.

TRUNK KIT- The factory trunk carpet does not include a decklid cover. Postons makes a monogrammed piece for around $100 which has your number on it. I was lucky enough to receive one as a gift and we installed it using 2" industrial Velcro instead of contact cement like they recommend. I'm not sure the Velcro will hold permanently, but so far so good.

 

Two issues to consider with this Poston piece- one is that the lines they give you for the foam strips don't line up with the frame of the decklid. The other is the color pattern- it's opposite the proper GNX- red/white scheme.

CONSOLE RISER- GET ONE! I don't know where I used to put my elbow without this thing. It really looks factory and it doubles the size of your console storage and even has a removeable divider. He can also add a retractable cup holder. I think Kirban Performance sells them now.

  (click for a link to the full size picture)

CARPET SAVER- I also received mongrammed carpet savers from RKKustom as a gift. They look great but I suggest using them only for shows since the white X soils easily.

Click here for a larger image

DOOR RUNNERS- Note also the runners in the above picture. I had a set of them powdercoated black and affixed a new Fisher body emblem.

HORN BUTTON- I had a custom "GNX" horn button insert made through BuickGN.com. This is NOT s cheesy sticker, but a solid replacement. You can specify whatever color scheme you want, I chose monochrome because it matches the interior. Looks better than the factory button and I used a Kirban billet horn ring which is also flawless. Both pieces are excellent quality and a highly recommend them.

RADIO- I'm not a big audiophile, but I wanted something better than stock. I installed a Jensen KDC-9520 "hi power"AM/FM/CD/Cassette deck. It is the only receiver I've found on the market that has the tape and CD onboard a stock-sized "1.5 DIN" package. It mounts with the stock brackets and even matches the factory grey. I wired up a harness so there would be no cut wires. The factory Concert Sound radio is now stored away safely. Crutchfield doesn't have this model anymore, but they have others. For example, the Pioneer DEH-P47DH.

SUSPENSION- I use Bilstein shocks, Kirban springs, and I installed the missing 3 & 4 body bushings. I also added the Kirban front brace kit and ATR urethane end links/bushings on the front sway bar. On the end links, I recommend re-tightening them once or twice until they take their shape. I highly recommend these upgrades to maximize the 15-yr-old suspension and save the old parts as you see fit.

REAR END FLUID CHANGE- Unlike the other G-bodies, the GNX differential has a fill port (3/8"square) and a drain port (5/16" hex) so there is no need to remove the cover to change the fluid. The differential holds 2-1/2 quarts of 80w/90 gear oil including the GM limited slip additive. The oil level should be right up to the fill port (it should spill out if you try to overfill it). You'll need to devise a little fill hose because the torque arm and exhaust make it tough to fit the quart bottle in there. I replaced the fill plug with a magnetic plug from Kirban.

WAX- I highly recommend Zaino Bros polish products because they perform second to none, are completely non abrasive, and outlast every other wax or polish. Zaino is not well known by the mainstream because they do not sell in stores. Despite that, they are rated #1 by enthusiast groups. You can learn more by searching the Buick boards, Viper boards, Corvette boards, GuruReports.com and of course ZainoBros.com. I recommend you purchase them from Carl at HCV Industries because he is a top-notch vendor.