After Tranny rebuild: 4th & 6th not engaging properly

[Tuneboy]

Hi,
so i had the leaking driveshaft seal which turned out to be the diff bearing.

I opened the tranny and fitted a new final drive, replaced every bearing and every synchro with mfactory carbon synchro and fitted acuity gear selector spring. I also installed hybrid racing shifter, new flywheel and new clutch.
Its my first time working on a transmission so.. At first i cracked the housing while putting everything back together, i found a new EP3 case for 250 GBP. Installed it today and.. well it does not work!

At first, the clutch is really really light but i checked that and its fully engaging and disengaging. But the main problem is that 4th and 6th dont engage.
Well, they engage but as soon as i give it some gas theyll pop out with a crunch. I tried at standing still to keep the leaver hold in 4th - the car is moving forward but as soon as i apply a miminum of gas, the gear pops out with a loud crunch.

1,2,3,5,R is working fine.

Does anyone have a idea what that could be?

 

[Fez]

I'd take the shifter unit off the top of the gearbox first and check thats all okay, also under the gearbox mount you have the 3 detent springs/bolts, check the springs/balls are still there/not damaged. I have seen them before where the ball has gone too far in to the bolt.
Another thing you could try to is adjust the throw on the shifter see if it gets better/worse

 

[Tuneboy]

I checked the balls and springs while i installed that and they looked like new.

Ive read something about a mainshaft adjustment. I guess ill measure the adjustment of the shaft but i have to open the box again ;_;