7.2 litre diesel, 6 speed manual transmission, when truck gets warm it is almost impossible to shift, any ideas? Shifts fine when truck is cold but warm I have to shut truck off to get into gear.

 

I believe your truck has a hydraulic clutch system. It does sound like there is air in the hydraulic system, which can be removed by bleeding the system. You might want to have the entire system and linkage checked for wear. Certain plastic parts wear and can cause other problems.