I just finished lubricating my intermediate steering shaft (ISS) yesterday and it fixed the clunking sound the plagues many GM vehicles. I went loosely off Colin Kraft's write-up here: http://www.colinkraft.com/shaft.php
His write-up is for a Monte-Carlo, but the general idea is the same, so I will be referencing it, as I didn't take pictures while I was doing it (sorry!)
The following is for an 8th generation Impala. The specific car I did it on was a 2007 with ~68,000 miles. It has been clunking for thousands of miles, but slowly getting worse.
Here's a few things you'll need:
Steering Column Shaft Lubrication Kit, P/N 26098237
A tube of grease from any automotive store. You'll use maybe ~1/20 of it
A wine bottle cork cut in half
15mm box wrench
Torque wrench (if you don't have one, doing this write-up instead of taking it in to get fixed will buy you a very nice one!)
A couple hours
There's only two bolts you need to remove, both are 13mm, but the one attached to the steering wheel has a 15mm nut on the other side. Removing both of these will allow you to pull it out from inside the car.
The first thing you'll need to do is make sure your front tires are perfectly straight. The lower bolt rotates with the steering wheel, so you won't be able to reach it if the tires are crooked.
You are going to need to jack up the drivers side and remove the drivers side tire.
Once the tire is removed, you can follow the tie rod back until you see a rubber boot covering a white plastic seal pictured below:
You will need to pry this rubber seal off. Underneath it you should see a 13mm bolt. Here's a picture from Colin's writeup:
Once this one is removed, you should be able to push up on the ISS to detach it. This will let the steering wheel rotate freely. Don't rotate it more than half-way.
Inside the car you will want to remove the black plastic underneath the dash. This is held in with 3 plastic push pins. There is one on each side of the front and on on the back on the right side.
To remove them, put a screwdriver underneath the center pin, this will pop it out. From here you should be able to pull the entire pin out pretty easily.
Heres a picture of the center pin pulled out on the top left part of the dash:
Once that is off, you will be able to reach the inside rubber boot more easily. Here's a picture of the rubber boot (with the black plastic piece still on):
You will need to pull the rubber boot inside the car off the white plastic seal to reach the bolt. Like underneath the car, you will need a 13mm socket. The difference here, is there is a 15mm nut on the other side. You can rotate the steering wheel half-way to put the socket on one side and a box wrench on the other.
Once this bolt is off, you should be able to push the ISS down through the rubber boot a little bit. This will disconnect it from the steering wheel. From here, you will want to pull down on the rubber boot so its underneath the white plastic seal. This will allow you to pull the ISS out from inside the car. It may take a little coercing and wiggling to get it free.
Once you have the ISS out, pull on each end so its fully extended. I wiped the old grease off wherever I could reach.
If you purchased the kit, you can use the syringe of new grease and squirt it down into the top end. Here's a picture from Colin's write-up:
The ISS in an Impala looks slightly different. The end we inject grease into has a "male" end, where it slides into a "female" end near the steering wheel.
I found this picture posted here: http://ls1tech.com/forums/attachment...aft-06-imp.jpg
If you just purchased a tube of grease, grab some fingers full and push them down into the end.
Once you got a bit of grease in there (a couple fingers full), use the cork included in the kit or the wine bottle cork that was cut in half to plug the end.
Here's a picture from Colin's write-up:
From here, you will want to fully extend and collapse the shaft 10-15 times to work the new grease in everywhere.
Remove the cork and clean up any that you may have gotten on the outside. You don't need to remove any from the outside portion of the smaller shaft that slides into the larger one. I personally put some more on the outside of this.
Once you feel it is better lubed and the cork is removed, you are ready to put it back in.
When you are putting it back in, make sure you put the "male" end towards the steering wheel. The "female" end on the other one has one portion that is threaded, make sure this goes towards the passenger side.
From underneath the car, work the "female" end back over the "male" end and insert the bolt. There is a small notch in the "male" end. If the ISS is not pushed down far enough, the bolt will not go through. According to Colin's write-up, this should be torqued down to 35ft-lbs. Do not re-attach the rubber boot on the plastic seal yet! (You might drop the nut on the top down the boot and need to fetch it from underneath)
The top portion of the ISS should be a little easier. You will need to pull on the ISS to extend it slightly to get it to fit together. You can rotate the steering wheel a little bit to help wiggle the male end in.
Once this is in place, you will want to rotate the steering wheel half-way again so you can put the nut on one side while holding the bolt on the other.
You can put a 15mm box end wrench on the nut and use a torque wrench on the bolt to get it to 35ft-lbs.
Once you have this torqued down, make sure the boot is back over the plastic seal (on both ends).
You can proceed to re-install the plastic portion of the dash underneath and put the wheel back on.
Before taking it anywhere, start the car up and rotate the wheels back and forth a few times. If you did something horribly wrong (I can't imagine what, as long as both bolts are back in), you should see both tires rotating.
Take it for a test drive and hopefully the clunking is gone!