Hey fellas. Just finished doing a quick swap out of a gearbox. My 5th gear completely let go in a catastrophic way. Bought this one only a few days back, the box let go on the way home. Got it cause the missus has bailed and the 75 series ute wont cart 5 kids.

So I've swapped out the box for a 2nd hand one, i know it was working alright before hand.... I left the original clutch on there as it wasn't slipping at all.
Now, after the first test drive, it's slipping. Anything to check before i rip the box back out or take a match to it? 😬
Also another thing i noticed, sometimes it won't allow you to select 5th? But other times it will. Box sounds fine. Any help would be appreciated.