ka tranny grind into 2nd gear

[daveh93s13]

my 2nd gear grinds when i shift it the slightest bit hard, as if i was "getting on it" during an acceleration. my question is i used 75w90 napa gear oil that said it was gl4 gl5 sufficient as i searched on here already and ppl were saying to use mt90. i could only find this stuff and thought the 90 in 75w90 would be ok. could this oil cause the syncros to grind? or could it just be a bad set of synchros? are the ka trannys tough? and lastly if i were to replace the synchros set is there tougher ones recommended?
thanks in advance,
dave