Gearbox Unwanted Rebuilt... 1st gear blocked??

[optane]

Hi everyone! I'm new to the forum and to morris world, and this is my first post. about 1 month ago I've bought a 1966 6 cwt Van. 1098 engine and std 4 speed box. Coz I want to use as a daily car, I'm doing some work on it, renewing gaskets and some other service parts.
Long story short, I've taken the engine and box out, and notice that the clutch bell housing was covered in oil... back of the engine/clutch and fly wheel all dry and clean...
So, I've decided to check the front cover inside the bell house, and noticed that it was quite worn out around the shaft and there was a broken washer...
Got a new modified front cover with oil seal, new washer to replace the broken one and so on...
Smartly I've turned my box 90 degrees.... and the layshaft made his way out of the box...
so, decided to put it all apart and take the opportunity to inspect the inside of the box... took side cover out, disconnected the remote control, and carried on taking things apart using the Haynes workshop manual... all came out nicely, all cogs are in excellent condition with no signs of wear at all.
all back together now, all spheres and springs and all in the right place...layshaft spaces front and back all in place...but:
i can engage all gears by hand, turn the main shaft by hand, and all it smooth and aligned... apart from the 1st gear. it goes and stays into 1st, but can't spin the main shaft! everything is solid blocked... put in 2nd, turns nicely, the same in 3rd and 4th and reverse...
So... any ideas before I take everything apart again pls?

tks a lot!

[bmcecosse]

How about reverse - does it work ? Maybe the reverse gear in wrong way round - I'm not sure if that's possible....but may explain.... Oh and read the EXCELLENT gearbox rebuild PDF shown in a nearby thread.....

[optane]

Yes, reverse work beautifully, engages and everything turns nicely.
Just found the PDF u mentioned! It's great!

[biomed32uk]

So with the box in the neutral position you can independantly rotate the input and output shafts?, and there are no gears catching at that point. You should be able to turn the shafts in opposite directions at will.

The only real way a box can lock solid just by gear selection is for there to be two gears selected at once.

I dont think its physically possible but the reverse idler is not in the wrong way round, as thats obviously involved with first gear, when first gear is selected if I remember correctly it will engage with the reverse idler as well, but does nothing as the idler is clear of the laygear, or should be.

If you have taken all the interlock balls and slugs out make sure they are all in the correct place, as they should physically block movement of other selectors when one is out of the neutral position. The box going into two gears whilst in motion would be catastrophic, you would probably get gears comng through the floor to join you in the car !.

I dont think it is your problem but you can overrun 1st gear, especially if you whack it over by hand, it will run past the detents and then jam in 1st gear, you can see the balls almost popping out of the hub.

Be interested to know what you find.