2 Speed Trouble

[max-nitro]

I have a duratrax maximum mt pro. The two speed seems to be locking in one gear or the other. I took it to the local hobby bench where their best tech played with it for about 1.5hrs and i never heard it shift, not saying i've never heard it but sometimes it does and sometimes it doesnt. Resently it seems to shift fine when its still cool, but when it gets warm you either can't hear it or its not doing it.

Please Help!!

[XXXER]

WELL, with 2 speeds, you can tell if it is shifting or not, if not, adjust it, i think it probably does, check the manual