I forgot where I got this info from (I think someone sent it to me), but never the less, it’s useful information if you have to accomplish this task!
Accessing the instrument panel of the Buick GNX is easy in the sense that the layout is simple, but difficult in that you have to be very careful – you’re dealing with irreplaceable parts.
The GNX uses a specific speedo cable and I’m not sure if it’s available anymore.
Allow 2+ hours and have a healthy supply of paper towels to avoid marking the interior trim with greasy paws.
Main parts – tub of white lithium grease and brush, 3/4″ wrench, 7mm socket (1/4 drive), 15mm deep socket (3/8 drive), 3/8 extension, phillips screwdriver, towel, paper towels, hand cleaner.
1 Disconnect the speedo cable at the “half-way” connection in the engine compartment with an adjustable wrench and a channel lock pliers. Straighten the cable going to the firewall to allow slack for pulling the instrument panel out. Lube the speedo cable to firewall with a tire dressing, like Meguiars Endurance.
2 Make sure the boost/vacuum gauge line going into the firewall also has some slack to feed.
3 Remove the instrument panel bezel plate and carefully store it in the back seat.
4 Remove the steering column/vent bezel (under the steering column) (two 7mm bolts)
5 Loosen the two nuts (15mm deep socket) that hold the steering column up; drop it as low as you can and still have a turn left so the column doesn’t drop.
6 Remove the 2 screws (philips) that hold the idiot light panel in place and tug it aside.
7 Drape a thick clean towel around the steering column to protect it. Remove the 4 bolts (7mm) of the Buick GNX instrument panel and start working the assembly towards you. It should move as the speedo cable allows. Ideally, a second person can feed it from the engine compartment. When it comes out far enough, use a 3/4″ wrench to disconnect the speedo cable.
8 Rest the instrument panel assembly and feed the speedo cable out to the left. This is where it gets messy and I would use towels liberally.
9 Slowly remove the speedo cable out from the sheath. Brush white lithium grease liberally onto the cable as you fish it back in using a twisting motion, about 8 inches at a time.
10 For the last 10 inches or so, use a paper towel to wipe the grease smooth. Too much grease can splatter into the speedo. Beside, it’s a straight shot and shouldn’t require much lubrication. Feel free to draw it out again and repeat to make sure enough lube stayed on the cable. When done, make sure there’s no glob of grease on the connector.
11 Now would be a good time to perform other projects while the instrument panel is open.
12 Lube the speedo cable sheath with tire dressing and then feed some back to the engine compartment. Re-connect the cable to the speedo and make sure there aren’t any kinks.
13 Reassemble in reverse order. Make sure to center the steering column as you tighten it back up. Test all lights & gauges before buttoning it up.