CK5 - The Full-Size GM Off Road Community

I have a '69 that I have no history on. The rear end has some probs though that one of you brilliant peoples should be able to help me with.
In reverse, if I turn too tight it hops and clunks and squeals and jumps and moans. Around tight corners in forward the rear squeals, but in a straight line everything seems fine.
I have heard buzz words like "bad locker" or "spooler", how can I confirm what is going on without paying a shop to open it?

I don't see what you described as a problem. I had to try to get mine to do that (I had the spiders gears in the diff welded). It just sounds like you have a tight limited-slip or a spool in the rear.
To see what you have got in there jack up one rear wheel and put the trans in N. Then see if you can spin the tire. Then tell us what it feels like.

I will try that when I get home. - Thanks.

turn one wheel, and the other spins the same way.

Sounds to me like it has a locker or welded gears in it. To find out for sure pull off the rear cover and take a peak (don't pay to have someone look at it unless, you live in Indiana, then bring it over to me)! It's always nice to know for sure what you have plus, then you will know when the rear diff. fluid was changed.

Try it again with only one wheel off the ground...sometimes you can get a LSD (limited slip device) to slip some, and a locker might free wheel. Or you could open it up and find out for sure what you have. If you do decide to open it up and it is a LSD you need to have "friction modifier" added to the oil when you fill it back up. The best stuff is the GM posi stuff.

if I open it, what am I looking for? how messy is it?
When jacked up I could go back and forth with one, maybe an inch or so of "play". Is that normal?

I would just look for a part # or manufacturer or something...just spin it around till you can read something and jot it all down. You might need to clean it up with some brake cleaner to see anything. Taking a pic couldn't hurt either. If it is your only transportation you might want to get the GM friction modifier befor you pop it open just in case, along with some RTV to make a gasket out of, and some gear oil. It isn't too messy it just smells bad.

1" of play is normal.

Before opening it up, realize that there's burnt cat pee inside of the thing, so you need to put a drain pan under the pumpkin before pulling the cover.

What you're looking for is the differential unit itself. An open differential will have a set of gears in it. A welded open will look the same, but the spider gears will have beads of weld added to the valley in a couple of places to prevent any differential action from taking place. A limited slip unit will have a set of springs (some have coils, some have an S-shaped leaf in them) in it, pressing against friction packs of some sort. A spool will be a fairly slim unit with no gears inside of it at all (it will be solid). A locker should have a fairly beefy looking case and you might see some sort of cogs inside of it.