Hey fellow mk3ers

On a cruise today was driving and everything was sweet, sun was shining fantastic....Come to a set of lights, took off from the lights and got to red line in first and then as I went to second it crunched HUH WTF @(#U@#(

I didn't think much of it as I wasn't sure. Did it again a few times , after that. This is going from first to second it crunches, I also took the second gear to just over 6000rpms and switched to 3rd and that was fine, as the other gears also!

What I couldn't get was I could take it to 5000rpms and it would not crunch from first to second but if I took it higher it was crunching not sure what it could be, can anyone help me!

What can be wrong I ask or your knowledge fellow vdubbers!!!