When I put it in 4 lo I get banging and knocking sounds coming from under the car. Any ideas?

 

If you only have 4hi and 4lo to choose from It's the VC in the transfer case.

 

but with the 249 doesnt it basically bypass the VC when in 4lo locking everything up?

 

It moves slowly. But makes alot of banging and and jerking.

 

No, 249 doesn't have low-lock.
It's your viscous coupler as stated above. It will get worse and jerk like that during turning in 4hi as well. Start looking for a new t-case.

 

So I have just had my transfer case and rear diff overhauled needed some bearings replaced. I have a 99 grand Cherokee 4.0L straight 6 and it's all time 4 wheel drive or the option of 4 Lo. Sometimes when I'm driving the truck feels like its driving "heavy" and sometimes it drives really smooth. I'm wondering if sometimes its in 4 wheel drive for no reason. How do I kno when it's in 4 wheel drive?

 

If its all wheel drive then its always in 4 wheel.

 

So its the Transfer Case?

 

Yes.

 

Big price?

 

It's not all wheel drive its a 4x4 but the quadra trac system is 4 all time and 4 lo n I was told it doesn't kick into 4x4 until the rear tires spin 1/8 of a turn so if that's true how do I kno when it actually goes into 4x4 n when it comes out of it?

 

Its all wheel drive.

 

my 2005 gc all time 4wdrive do it help to turn off when road is hot , dry and dusty? will help gas millage when turned off whas best position to be in ?? thankx