Strange malfunction--HELP!

[kodiak kid]

I've had my Vanguard 6x6 for 8 years, but I have always pampered it, kept it in the garage, and maintained it by the book. And it does not have that many hours on it. Last Wednesday a friend of mine and I were crossing a swampy area to go to our duck blinds to repair them before the season opening. Two hundred yards from the road and the trailer, as we were going over a very small log the Argo stopped. The left wheels were in the air and turned, but the right wheels were not moving, even when I revved the engine up. I looked at the idler chain sprocket (the upper one, the one that transfers torque to the wheels) on the right side, but it was not moving. We winched the Argo onto even terrain, and with all wheels on the ground only the left ones had traction. The right wheels were not locked, but were not pulling, either. We managed to return to the road using only the left wheels: to steer to the left we had first to turn right and describe an almost complete circle until the front end pointed in the right direction. Getting the Argo back on the trailer took several tries. Well, I went back home and put the Argo in the garage, trailer and all. Yesterday I needed to get the trailer out of the garage, and when I drove the Argo off the trailer I noticed that the right wheels were working again. I drove the Argo in tight and fast circles in front of the house, going counterclockwise, and obviously the right wheels were pulling hard.
Can anybody figure out what happened? I certainly do not dare to leave the beaten path with my Argo the way I used to, fearing that the same thing might occur. Unfortunately I don't have an Argo dealer where I live (Kodiak Island), and my mechanic is good (he works on all kinds of vehicles, boats, ATV's) but doesn't have much experience with this kind of vehicle, though he's worked on mine a few times to tighten idler chains, change oil and filter, mount the winch, etc.
I would appreciate any advice I can get.
Thank you.

[plott hound]

is that brake locked up?are the chains all on? either that or you have a transmission problem.hope this helps.

[kodiak kid]

Thanks for your answer. No, the left brake was not locked up, as the left wheels turned freely once the Argo was on level ground. And the chains are all tight and engaging the sprockets properly. I believe it's a transmission problem. I looked at the transmission diagram and I saw that the sprocket/brake disc assembly (the one which imparts the motion to the idler chain) is held to its shaft by two internal keys. I'm beginning to suspect that these keys are worn and may not lock the sprocket to the shaft all the time. If that's the problem, it's going to be fun taking out that part, since it would be necessary to remove the left brake first. Working inside an Argo is always a pain in the donkey. You hardly have any room to stick your fingers in it...

[MAX IV Mark]

I dont have an Argo so I could be off base here. But it sounds like a collapsed hydraulic brake hose. As I understand the previous (non admiral trans) it is just a differential with brake steering. If a key is bad on either output, you would lose both sides of movement not just one. If they have bleeders on the brakes, I would try to gravity bleed them, the one that wont bleed has a bad hose. Next I would look for a stuck caliper. Not sure if this will be any help or not.
MAX IV Mark

[kodiak kid]

I dont have an Argo so I could be off base here. But it sounds like a collapsed hydraulic brake hose. As I understand the previous (non admiral trans) it is just a differential with brake steering. If a key is bad on either output, you would lose both sides of movement not just one. If they have bleeders on the brakes, I would try to gravity bleed them, the one that wont bleed has a bad hose. Next I would look for a stuck caliper. Not sure if this will be any help or not.
MAX IV Mark

Thank you for your reply. The Argo does not have hydraulic brakes. They are mechanical. Besides, if the brake on the right side had gotten locked, the vehicle would have gone in circles. Instead, though the right wheels did not pull, they were turning freely while the right wheels pulled. But I think you are right when you say that if the key on one side is bad power would be lost on both sides. I don't know what happened. I only know that when I was stuck and raised the hood I noticed that the sprocket/brake disc assembly on the right side was only slightly twitching when I revved up, while the left wheels were turning just fine while in the air. This at least excludes the disengagement of the chains on the right side. If they had somehow lost contact with their sprockets, the output sprocket/disc assembly would have spun.

[spookum]

how to check for a sheeard key (assuming your trans uses sheared keys and not splines.

make sure the engine is OFF. make sure the trans in in gear. shine a bright light betewene the trans and brake flange. Turn the clutch on the trans over by hand. I bet you will see the shaft turning, and not the flange!

FYI new keys are less than a dollar each Some machines take two, some only take one.

good luck and keep us posted!!!!