strength of open diff 8 3/4?

Any time you're on the gas it's locked or close to it. Slow turns with almost zero throttle it'll behave until you touch that throttle. It's very sensitive.

Getting on and off the gas results in a tail wiggle that gets worse with speed. It's probably like a spool but I haven't owned one.
I've never gotten used to it

On the plus side, it looks almost brand new with 10k miles of use. It's heavy metal for sure