I have a 2nd gen dodge cummins.when I put it in 4wheel drive.trany goes but only two wheel drive .anyone.help please

 

I'd bet it's the axle disconnect on the passenger side. Common problem.

Mopar1973Man's Dodge Cummins Articles - Central Axle Disconnect (CAD) System Troubleshooting

 

Will it hurt to drive it makes a horrible grinding backing sharp

 

Horrible grinding is never a really good thing.
Pull the vacuum actuator and plate, see if the actuator is working.

 

Ok .where is this located yjay.and thanks man.

 

I have the same problem with my actuator acting up if y'all figure it out please let me know

 

There is a couple of vacuum lines that run to the actuator, it is located on the passenger side of the axle tube, there is two shafts and a collar that slides around. The actuator pulls the collar to lock the two shafts. The vacuum lines rust out or break. #1 solution is a new actuator, but if something has an issue all the time why put a new troublesome part back in? You don't! Posilok.com I believe that is the site, been along time. They were about 200$ but worth every penny! Switches it over to a cable system and all of a sudden a dodge part that will always be a pain in the *** is now pretty much bullet proof! Good luck fellas

 

check does your heat change from floor to windshield and then to cabin vents? if not its defiantly a vacuum leak. I had a problem with the rubber lines dry rotting on the driver side of the motor right in front of the fire wall. also check the metal lines that run along the rail like just another diesel guy suggested.

 

Mine did the same thing a couple months ago and it ended up I had just knocked the game line out of the power steering pump when i was doing my fuel filter I reconected it and haven't had problems since

 

Just buy a posi lok kit. Its a manual actuator. They never fail