A833 Four Speed Gets Stuck in Reverse

Hang on, when you push the cover up........ it has to stay up,while you tighten the long-shoulder cover alignment-bolts; at 3 and 9 o'clock.

Ok so now
Part one; external
First; make sure the engine mounts are secure, and that the clutch is NOT dragging.
Second; make sure that engaging reverse with the stick, is over to the left towards your knee; and UP! away from you,towards the dash.
Third; make sure the reverse link rod is not getting stuck on any other part of the linkages. You know, cotterpins, or the adjacent swivel, or the link-rod is rubbing on the case,and such.
Fourth; make sure the external lever is not over-centering because it is on backwards or because it's the wrong lever.
Fifth; put the trans in Neutral
disconnect that link-rod from the shifter. Now shift it into reverse from the cab and pull it out several times. This to make sure it is not a shifter problem. There are over 40,000 ways to put that shifter back together after a rebuild, and only one is correct.

THEN
Part two; internal
Pull the linkrod off the trans lever, and;
By hand, shift the reverse lever in and out, sorta gently,attempting to feel resistance. The first time in, the teeth might butt up against each other, so don't count it. But from that point on it should snick in and out nicely. If it does, then the problem is NOT internal , so go back to part one.
>But if it is still sticky, then drain about half the oil and then back off the reverse detent plug, and repeat the shift test. If now it is free,then lets go after the why of that. The first thing to do is to fish that ball outta there and measure it. IIRC it is supposed to be 3/8 inch. A too-small ball can jam up the internal comb if it comes out to far down there. The next thing is to make sure there is exactly ONE gasket on the whatchamacallit spring-tube, and last;make sure the spring is not crippled somehow. If the spring tube has been withdraw too far off the comb, by perhaps too thick a gasket, then the ball can try to sneak out the bottom. A correctly sized ball cannot actually get out, but a too-small one might try to.
>But if it is still sticky; Now the cover bolts have to come out,so drain the rest of the oil. Then remove all but the two bolts beside the reverse lever on the horizontal run. Once all the shouldered bolts are out,loosen the last two plain bolts just a smidge, enough to bop the cover up. It will now move quite a ways. Keep it up and tighten those two enough to keep the cover up. Then try the reverse lever again, now with the reverse detent plug completely off.Ok now we have eliminated the interloc, the detent, and all external possible sources.
>But if it is still sticky then there is only one thing left; the gear is sticking on the shaft, or the shift-fork is sticking in it's boss, or the internal lever is sticking in it's bore, or the comb is rubbing on something. Since there are only two bolts holding the cover on, it would be easy to just pull it off,and check all that internal stuff. And if you find the problem there, then, there is only one cure..... complete tear down,to remedy it.

Ok, I think I covered it all, so good luck.
Well I thought of one more but if no parts were changed, it's irrelevant,lol.