Lately, whenever the transmission is engaged in forward, without revving the engine, it kinda grinds in till the lever actually engages. I have fresh oil in the tranny. What could be causing this?

 

Your idle could be too high or you may need to adjust the linkage a little bit.

 

The idle is fine. How do I adjust the linkage?

 

Look at the rods leading from the shifter box to the tranny, there should be some threads and nuts, loosen the nuts and turn the rods until it locks positive into gear, then tighten the nuts back and you should be done. Of course this is assuming that it is only an adjustment problem and not internal.