Dana 60 question regarding burnouts

[Mike C]

What does your SPID say? What sort of tags are on the rear diff? Usually a posi even a worn one does two wheels when you get on it but one possibly power breaking.

In 68 would have had a PowerLock for an LSD which is very well thought of and durable. And they increase pre-load on clutch packs under load. This could explain the two track when power breaking.

The 70-72 diffs would have likely had a TrackLok which is not known for being 100k mile durable. But they are cheap and easy to rebuild.

Added: 50+ year old truck most likely needs a diff fluid change... why does no one ever just pull the cover, inspect their diff and refill with new, clean fluid and appropriate additive? I think this is a weekly new thread anymore.