The brakes are located next to the differential, so if you hit the brakes, the braking power goes through the half shaft, & geared hubs before stopping the tires. If you should have a wheel in the air and you hit the brake too hard, you can snap a half shaft in two. And in order for you to continue you may need to remove the shaft to prevent too much other damage from the broken shaft. I found removal and replacing the shaft is easier then I had imagined it would have been.
I myself have not broken a shaft yet, but for the second time now I have seen the ball race within the Constant Velocity (C/V) joint break. My first one broke while making an emergency stop, but chances are it may have been cracked before I stopped. The second one did not break to the point where it was not drive able, but I could hear a little knocking noise while hitting the brakes while coming to a stop.
Update: Finally broke a shaft while on at the February 99 Bit Texas Outing at Fort Hood. But for some reason I think I weakened it while pulling a semi out of some mud and my climb up the left side of Chicken Foot gave it the extra push it needed to brake the shaft in two. The night before, and early that morning I heard some funny clicking noise and I had a feeling it was going to go. In fact at breakfast I said that I may brake my right rear shaft, and I did.
I first thought it was my front shaft because the boot to the outer C/V joint broke open and got a temporary boot cover to fit it until I had the time to go in a repair it correctly. Well I figured that too much dirt & water may have got into it, so I ordered a new right front haft shaft. After I installed it, the noise was still there, so knowing it was on the right side, I removed the right rear half shaft. Just as I removed the axle and stood the outer C/V joint up, water came out of the boot. One of the clamps was not too well sealed, and after removing the boot and checking the joint, I found a small crack in the retainer ring.
So it was either buy another half shaft or see what I can make from the parts I could use from the old front half shaft. I removed the outer C/V joint from both axles and cleaned and repacked the one that was once the front outer C/V joint. Installed it on the old rear shaft, and re-installed. Test drove it and every thing was once again in working order. The whole job on the long run worked out very well for me, I knew I had to replace the boot on the right front C/V joint, and by replacing the whole shaft, I fixed that problem. The parts from the front where in good condition and where used on the rear, the boots on the rear was in good condition also, so with new clamps on the boot, fresh grease, and the C/V joint from the old front, the rear was repaired at a cost of $5.00 plus my labor.
The Hummer service manual only talks about taking apart the inside C/V joint, and does not say anything about the outer one, other then to pack it with lithium grease. They treat it as a non serviceable item, but I feel and know other wise.
Click on the photos for larger image.
|In order to get axle out the access plug to the "halfshaft retaining capscrew" must be removed so that you can remove the bolt that is holding the C/V joint in the hub. Here the photo shown it removed.|
|Here is the differential with the brake rotor still on it. There are 6 bolts that old in the inner C/V joint to the rotor / differential. For a better view of this with the axle in place look at the Bridge City Fire Hummer page. If you have the under carriage protection, I think you can still remove the H-S, but it is not as easy. I had to remove the E-brake cable to get enough freedom to get the H-S out.|
|Here is the old and new C/V joint. As you can see, dirt has created a grove in old C/V joint, if it should get to bad, it too will have to be replaced. Before re-installing an old joint like this it is best to clean it up and make sure it is nice an smooth. And a new seal should be used.|
|Here is a view of the old seal still in the hub.|
|This was the old front C/V joint. It was still good and greasy. It was then taken apart and cleaned. And re-assembled for use on the rear shaft.|
|At the end of the shaft, you can see a small ring. This ring is what holds the C/V joint to the axle. By either pulling on the C/V outer case or tapping with a small hammer on the inner race, you can get the shaft to come out. This photo here also show the inner "C" clip removed, but did not needed to be.|
|Here is the C/V joint after being taken apart and cleaned. It is now
ready for re-assembling and packing with lithium grease. Part names are
on the larger photo.
In order to take apart the C/V joint as I did, you must first remove the shaft, I used a small hammer and tapped the inner race, until it came off. Once the shaft is out, you can turn the inner race to the side to remove the balls. Once all balls are removed you will have it like I did here.
|This was the old C/V joint. As you can see the ball race is cracked. I made it bigger so that it could be seen here better. The balls and most of the old rusty grease & water was removed. None of the old parts of the old rear joint where reusable, damaged beyond repair.|
|Here is the re-built halfshaft ready to be installed. Some of the clamps can be removed and re-used, but if they break or are not reusable, you can get new ones for a few bucks from your local auto part store as I did here. Make sure all your clamps are tight so that no water can get in as it did in my case.|
|Here is the hub, before the shaft was installed.|
I wish I had known this earlier, it would have saved me a bunch. So far the one shaft the I got from then is great, and came with out a mark! MUCH better then the rebuilds that I got so far for about the same cost. I will never have a shaft rebuilt be the local shops again as long as NAPA can get them for me.
From what I hear the half shafts are now built by GKN and starting on 97 1/2 Hummers, they are now 20% stronger then the earlier half shafts and will fit the older Hummers. More Info at "Haft-Shaft - Old & New Comparison"
NAPA part # are
|Left - NAPA||Right - NAPA||Left AMG 97.5||Right AMG 97.5|
|Front||7899 NCV||7898 NCV||12342974-1||12342974-2|
|Rear||7897 NCV||7897 NCV||12342974-3||12342974-3|
But since I had posted this info to the web, the supplier has not be able to stock or get enough old units to refurbish, so their stock is very limited.
Another supplier is Southern Axle Exchange Inc. and they even have an easy exchange program just for the Hummers. This would be your best choice if you are looking for half-shafts for the Hummers. You may also want to check with the for the drive train and intermediate shaft for the steering. (Contact Scot Smith at 800 789-2953)
NAPA Auto Parts - Willow Brook
11414 Jones Road
Houston, Tx 77070
Contact Sales person: Shane,
In the event that you find yourself with a broken half-shaft, and
you must keep going, you will need to remove the broken shaft if broken
so that you do not tear anything else up while drive out. In order
to remove the shaft you can do one of two things:
My Haft-Shaft Repair Kit