Gears in my manual transmission Ford Ranger are difficult to shift when the engine is running. Why is this?

This usually happens in the morning or if I have not driven in a while usually when its cold out. Once the car gets warmed it gets easier.

Clutch, gear linkage or high idle.

Difficulty moving the shift lever only when the engine is running makes me think that the clutch is not disengaging completely.

If it's a cable clutch, check its adjustment. If it's an hydraulic clutch… I think I'd suspect a failing clutch master cylinder, or slave cylinder.

Switch to synthetic manual transmission oil. Redline MTL or Royal Purple Synchromax will solve your problem.

Hi so wear in both engine and gearbox are the usual cause of such issues.

Either you have air in the hydraulic clutch system or the pilot bearing in the flywheel is bad and the transmission input shaft is binding and continues to spin.

Gear oil gets thicker when cold, it warms up in a fairly short time of driving. This is when double clutching comes in handy. Depress clutch switch to neutral, release clutch. Depress again and put in next gear. No gas between.