Currently setting up Dana 80 rear end. We get it together you can turn the rear either way with the pinion with easy but if you try to turn it byHand on ring gear rolls backward fine but you can not roll forward. Then you can put in axles and try to roll it backward fine lockes up forward. We have tried rolling with only pinion it rolls fine. I tried rolling it with only ring gear in it with or without axles rolls fine. I have set the pinion depth deeper than it’s supposed to be and also shallowe than it should be and when ring and pinion are both in it it is locked up forward. I even set the back lash out as far as .060 still same result. Any ideas? Yukon spool,gears and axels all new

Did you verify that the ring and pinion gears have the original matching # gear set etch into both of them? If not do that next
If they have them you should be able to get them set up properly
If not a matching # gear set you are on your own
Are you using a pinion depth tool or trying to go by the pattern ?

How tight is your pinion preload? So how does it turn by hand when you grab the ring gear and rock it back and fourth? It sounds like the pinion is binding on the ring gear. How was your pattern was it in the middle? Did you try and coat the teeth with super slippery grease yet?

Gus

I think what you're experiencing is the nature of hypoid gears, especially dry gears. It "locks up" forward because you don't have enough leverage when turning the ring gear.

Hypoid gears slide against each other. I've experienced this with smaller rears as well when the gears were clean and dry. Try a spritz of WD or something with some lubricity. Doesn't have to be dripping wet, just not bone dry.

I am sure that hi gear ratios, like 5.38 increase the resistance a bunch by turning the ring gear as the pinion spins much faster.