yes it could be that but i had the same problem on mine too and it was a leak in my intake manifold gasket, it only costs about 10 on eBay and replacement is somehow difficult but it can be done, after that, everything was working awesome!!
If it is an electric fan, NO. If it is a mechanical fan test it to see. If you can turn the fan by hand with the engine not running it has a clutch.
Clutch disc, pressure plate, transmission shaft,
Generally if it is a thread on fan clutch, yes.Generally if it is a thread on fan clutch, yes.
If it will go into gear when the engine is off but not when the engine is running, the clutch is not disengaging. It could be the clutch, possibly warped or put in wrong, or it could be the hydraulic clutch mechanism.
Of course your clutch and/or gearbox are faulty...
The springs around the clutch plate have probably came out and locked up between the pressure plate and the clutch plate and locked them together. you need to change the clutch plate and have the pressure plate checked for damage.
The purpose of a clutch on a vehicle is to disconnect the drive of the engine from the gearbox (this would be required when the vehicle is stationary or to change gear). While the engine is running the crankshaft is continually turning, It is the crankshaft that turns the gearbox and via the gearbox the road wheels. Obviously there are times when the engine is running but drive is not required, The clutch is the mechanism by which this is achieved.
Unbolt the engine lift it up and turn it to the side where u see the tranny, unbolt the transmission, unbolt the pressure plate from the flywheel, take the clutch out, when u put a new one in make sure to use a clutch allingment tool
to do this, you need to enter the code, then whilst the engine is running, you need to remove the fuse marked BIC/Ilum, turn the engine off and on and then replace it, the drawback with this, is that the engine management warning light will flash when the engine is running at below 1500rpm, also the immobilizer light will flash, this can be turned off by holding in the central locking button for a few seconds.
Why don't you take it to a mechanic before you ruin your truck by riding the clutch? The chattering could be engine knock because your engine is out of tune. When you ride the clutch, the clutch slips and puts less strain on your engine as you are burning out your clutch.
If it will shift when the engine is off, but not while it is running your clutch is not working
You don't you pay the nearest shop $1100.00- $1400.00 to do it for you. cause you have to have air tools (and know how to use them with out cross threading any thing), an engine hoist and help .