Mine does this too. More noticeable when cold. If I try to speed shift when cold It will grind a bit. Have to wait for synchronization. I use Synthetic oil (RED LINE Mt-90) which is specifically for manual boxes and is not a slippery as some oils just to help eliminate this problem. Bottom line: It seems to be normal for KIA Sorento (a review I read stated the manual trans was clunky) and, in my experience with truck manuals, really performs about the same as other I have recently owned (2003 Hemi Dodge and 1993 Diesel Dodge trucks). The 1-2 shift is always a bit harder becasue the 2nd gear synchronizer has least mechanical advantage (the braking effect of the synchro on the clutch disc, input shaft and countershaft is, in terms of torque, the least relative to the required torque to accompish the speed change in a given time-that is why you might have to wait to finish the change).

 

Have you tried changing the gearbox oil for auto transmission fluid....this is a regular trick on Land rovers when the syncro gets a bit weak...its easier to squeeze out on the syncro ring/clutch particularly when cold...Auto trans fluid is a top rate lubricaant and used in many manual transmissions as original fit.

 

Thanks for the tip it definately sounds like its worth a try, has anyone else tried this and got a noticable difference?