Help!!! its my transmission

[lostinla626]

ok I am having some serious problems with my transmission but i dont know what it is.. i just had it rebuilt... i have a

s14 '96200,000 miles on engine and transmission only engine mods are cold-air, catback ex. and racing plugs.. ( forget which kind)Manual transmission

.. OK when the car is in neutral the transmission will do a loud grind.. for a second then stop.. but ive noticed the grinds are getting longer.. what is it?? the transmission also makes alot of noise when driving at low rpm and between shifts.. is it a lost cause? what should i do and what is it.. this also happened on my s13?? did i throw a rod?.. pls help

[navysnail]

make sure it has fluid, sounds basic but its a good starting point, then go from there.

[NISTECH]

Did this start typically only happening when you first started it in the mornings or after a long cold soak[not started for several hours]