Mystery part on rear driveline

[AirSpeed]

For the last week I have been hearing a strange sound coming from the rear of my 72 GMC 4X4, it was a clanging sound that today started making an additional squealing sound. I searched all over under the truck many times through the week and finally today found what I think is the culprit. There is a circular steel half donut shaped piece on the yoke coming out of the transfer case, the "hollow" side is towards the transfer case. I'm guessing it's there to protect the seal on the transfer case? I dont know but I would like the noise it makes to stop! Is this part supposed to be attached to the yoke somehow? Is it supposed to spin with the yoke? The squealing sound is from it spinning on the yoke until it catches up with the spin as I accelerate, the clanging sound I assume happens when I accelerate as well, I think it happens when it spins with the yoke and taps against the rear of the transfer case.
What can and should i do with this part to get it to stop making noise? I also want to change the lube in my NP205 and the front and rear axles, Do I use 80/90wt gear oil? Thanks for any suggestions! Aaron

[junkyardjohn]

I HATE STRANGE SQUEELING & THEN CLANGING SOUNDS. ESPECIALLY WHEN THEY'RE COMING FROM ONE OF MY TRUCKS. IF YOU CAN TAKE A PICTURE... IT WOULD BE WORTH MORE THAN 1000 WORDS OF TRYING TO EXPLAIN YOU'RE PROBLEM. THE FIRST COUPLE OF TIMES I DRAINED NP205s THEY WERE FULL OF ATF. IMAGINE THAT?? THAT WAS ALONG TIME AGO & BEFORE I JOINED THIS KNOWLEDGABLE BOARD, AND DIDN'T HAVE ANYONE TO ASK FOR ADVICE. & I WAS ABOUT 25 YEARS YOUNGER. DURING THE FIRST CHANGE I JUST ASSUMED A NIMROD P.O. HAD PUT IN THE WRONG FLUID (YES ON THE 90 WT. GEAR OIL) BUT AFTER THE SECOND ONE ON A DIFFERENT TRUCK??.. WELL IT WAS QUITE A MYSTERY. BOTH WERE AUTOMATIC TRANNYS ALSO.. JOHN

[Blazer1970]

Yes, that is to protect the seal and it is pressed on to the yoke. It is common for them to come loose like that. It probably will not just press back on now since it is hogged out from spinning on there.

[68C15]

^^^^^^^
correct. it can be removed but be carefull to not drive in tall grass or anything else that could damage the seal.

the lube depends on climate operated in. warm climates can use 80w90 but for the cold I would use ATF.

[junkyardjohn]

ATF IS NOT SUPPOSED TO BE USED IN THESE OLD NP205s. THEY ARE GEAR DRIVEN. THE REASON MINE WERE FILLED WITH ATF WHEN I DRAINED THEM IS BECAUSE THERE ARE TWO OIL SEALS.. BACK TO BACK IN THE ADAPTER HOUSING BETWEEN THE AUTO-MATIC TRANNY (EITHER A T-350 OR A T-400) & THE NP205 TO KEEP THE ATF IN THE TRANNY FROM MIGRATING INTO THE TRANSFER CASE. WHEN THESE SEALS FAIL.. THE ATF GOES INTO THE T/C & PUSHES THE GEAR OIL (80 OR 90 WT.) OUT THE OVERFLOW AND FILLS THE T/C WITH ATF OUT OF YOUR TRANNY. ONCE IT IS REPLACED WITH ALL ATF IT WILL QUIT. IT LEAKS OUT THE OVERFLOW ONLY WHEN THE TRANSFER CASE IS SPINNING SO YOU DON'T NOTICE A BIG PUDDLE IN YOUR DRIVEWAY. I LEARNED THIS MYSELF THE HARD WAY. NEVER UNDER ANY CIRCUMSTANCES FILL A 205 WITH ANYTHING BUT GEAR OIL. THE NEWER MODEL CHAIN DRIVEN NEW PROSESS T/Cs LIKE THE 203 OR 208 TAKE REGULAR OLD ATF, BUT IT DOESN'T HAVE THE LUBRICATING PROPERTYS TO PROTECT A GEAR DRIVEN T/C LIKE A 205 UNDER ANY KIND OF LOAD OR EXTREEME HEAT. DO SOME RESEARCH ON IT. I LEARNED ABOUT THIS MYSELF BACK BEFORE WE HAD COMPUTERS (IT WOULD BE EASY TODAY)& READ SEVERAL BOOKS & SERVICE MANUALS ON THESE TRANSFER CASES,(ALL THE WORLDS KNOWLEDGE IS CONTAINED IN PRINT ) BECAUSE I DRAINED TWO DIFFERENT ONES WITHIN A COUPLE OF YEARS & BOTH WERE FULL OF ATF & I'M NOT MUCH OF A BELIEVER IN COINCIDENCES. I WAS QUITE PERPLEXED UNTIL I LEARNED THIS. WITH A LITTLE ANNUAL MATENANCE THESE OLD CAST IRON NP205s WILL LAST FOREVER, BUT YOU HAVE TO HAVE THE PROPER LUBE. WERE TALKING ABOUT 1960s TECHNOLOGY HERE. IGNORE EM... & THEY WILL FAIL. JOHN