I have a 2005 ranger 5 speed 4.0 4wd. It won't shift with the engine running.If you turn the engine of put it in gear then the tuck will drive. Any ideas of what the problem is?

 

You have air in the clutch system and need to bleed it

Open hood first and check level in the Clutch fluid reservoir, next to power brake booster
Clutch fluid is Brake fluid Dot 3

If it is empty then you may have a leak in the system, top it up and try to bleed it(get the air out)

Google: Ford Ranger clutch bleeding

They can be very troublesome to bleed, so have patience


How a clutch works
The transmission is ALWAYS connected to the back wheels
So if truck is moving so is the transmission, there is no disconnect for that

If engine is running then clutch is turning at the same RPMs, so 700RPMs at idle

If truck is stopped, so transmission is at 0 RPMs, and engine/clutch is running at 700 RPMs, then we have a problem, we either need to slow down the engine or slow down the Clutch to 0 RPMs to match rear wheel/transmission RPMs
Shutting the engine off works, 0 RPMs, but not the best solution

Which is why there is a clutch
When you press down on the clutch pedal it pushes out a piston(slave) in the bellhousing which unclamps the clutch disc
The clutch disc is sandwiched in between the flywheel and pressure plate, which both spin at engine RPMs.
If there is air in the system then when you press down on the clutch pedal the piston won't move very much, so clutch disc is not fully unclamped and can not slow down to the 0 RPMs needed to put transmission into a gear when stopped.

When you are moving then you just need to match RPMs which is much easier than slowing clutch disc down to 0 RPMs