2006 Dodge Ram 2500 4x4 4WD issue

[amtc]

I have a 2006 Dodge Ram 2500 5.9 cummins 4x4 auto with a NP 273 transfer case. When I engage 4wd and 4wd low I hear a rattling noise under the truck. It is worse when there is no power applied. When power is applied the rattling noise almost goes away. When I am in 4wd low and stop and switch to 2wd the 4wd low light extinguishes and the front axle disengages. When I switch from 2wd to 4wd on the fly the front wheels engage, the 4wd light comes on and the rattling noise begins. When I switch from 4wd to 2wd on the fly the 4wd light extinguishes but the rattling continues and the front axle is still engaged. It will not disengage until I stop the vehicle. In 2wd the vehicle performs as it should with no rattling noise.

Currently, I have replaced front wheel bearings, left and right front axle u joints, front drive shaft, rear drive shaft u joints and recently had the transfer case completely disassembled, inspected, new seal kit and re-installed. The shop said it was the cleanest transfer case they ever disassembled with no wear. I am at a loss as to what it can be as is the transmission shop.

I contemplating replacing the electric solenoid due to the 4wd remaining engaged even when I shift out of 4wd but before I do that I wanted to ask and see if there is something else I should be looking at? Any help will be greatly appreciated.
Jim

 

[Darkbloodmon]

Is the T case a shift on the fly unit? I always come to a stop and let it roll with my NP271 manual selector.

Did the shop go through the shift motor or mode sensor on the T case or just the hard internal parts? Sounds like an electrical issue unless someone chimes in its not a shift on the fly type case and that this is normal.

The shift mode selector on the dash is a resistor unit it could be old worn/corroded just like any other resistor.

Could be more trouble than its worth to dig into it if this isn't normal operation; if all you have to do is come to a complete stop then roll forward or backward a bit but thats just my .02

 

[amtc]

Is the T case a shift on the fly unit? I always come to a stop and let it roll with my NP271 manual selector.

Did the shop go through the shift motor or mode sensor on the T case or just the hard internal parts? Sounds like an electrical issue unless someone chimes in its not a shift on the fly type case and that this is normal.

The shift mode selector on the dash is a resistor unit it could be old worn/corroded just like any other resistor.

Could be more trouble than its worth to dig into it if this isn't normal operation; if all you have to do is come to a complete stop then roll forward or backward a bit but thats just my .02

Yes the transmission is a shift on the fly model. I don’t mind coming to a stop to shift into 2wd but the rattling noise drives me nuts and I know that’s not normal. The shop just replaced the seals. They said the case is flawless. No wear, the chain is in great shape and only the rear seal was leaking. I’m wondering if the gears inside the transfer case solenoid could be loose?

 

[Darkbloodmon]

Yes the transmission is a shift on the fly model. I don’t mind coming to a stop to shift into 2wd but the rattling noise drives me nuts and I know that’s normal. The shop just replaced the seals. They said the case is flawless. No wear, the chain is in great shape and only the rear seal was leaking. I’m wondering if the gears inside the transfer case solenoid could be loose?

I would get it on stands run the 4x4 through the modes and listen to pinpoint where the noise is coming from.

 

[amtc]

I would get it on stands run the 4x4 through the modes and listen to pinpoint where the noise is coming from.

I had three guys at the transmission shop put it on a lift and try to isolate the noise. They thought it was the transfer case and tore it apart and found nothing. 1500 dollars later I got a new seal kit and the transfer case re-installed with the problem still there! Unfortunately I do not have a means to put it on a lift and isolate the sound. I am thinking about doing a process of elimination. If I understand the system properly I can select 4wd, secure power and go underneath the truck and remove the solenoid and drive it and see if the problem continues. If so then I will re-install the solenoid and remove the front drive shaft, engage 4wd and take it for a drive. If that's not it I guess I can have a driveline shop look at the front axle. Or sell it!

 

[amtc]

Update on my 4wd problem. I removed the new front drive shaft and installed my old drive shaft and the problem went way. Expensive lesson but I am glad that issue is resolved.

I do have a question about how the NP 273 transfer case works? I have the electric shift on the fly system and when I am driving and turn the 4wd selector knob to 4wd the system engages and works fine. When I select 2wd while driving the 4wd light extinguishes but the system remains in 4wd until I stop, put it in reverse and back up a couple feet then put it drive. I thought the system should go into 4wd and 2wd while moving?

When putting the truck in 4wd low I come to a complete stop, put the truck in neutral, select 4wd low and then put it in drive. When going out of 4wd low I stop the truck, put it in neutral and select 2wd and the system operates normally.

 

[Ozymandias]

Something is wrong with your system, should shift on the fly between 2Hi and 4Hi, both directions.
Very different tire thread wear?

 

[amtc]

Something is wrong with your system, should shift on the fly between 2Hi and 4Hi, both directions.
Very different tire thread wear?

Thanks for the reply. I do not have any tire thread wear. When shifting from 4Hi to 2Hi on the fly the 4wd light extinguishes and to be honest I thought I was back in 2WD until I made a sharp turn, that's when I noticed the front wheels were still engaged and the front end was binding during the turn. Had I not turned I wouldn't have known. I am wondering if the electric actuator is not fully dis-engaging 4wd?

 

[Ozymandias]

Means you have four brand new tires on the truck?

Because not disengaging means you must have a lot of tension in your drive train, mine is disengaging even in slight corners, your hear a snap from the belly a second after turning the knob and the 4wd is gone. That electric shift motor is quite powerful.

Are you the first owner of the vehicle?

 

[amtc]

Means you have four brand new tires on the truck?

Because not disengaging means you must have a lot of tension in your drive train, mine is disengaging even in slight corners, your hear a snap from the belly a second after turning the knob and the 4wd is gone. That electric shift motor is quite powerful.

Are you the first owner of the vehicle?

 

[amtc]

No, I have owned it since 2018 and put about 100k miles on it. I dont use 4wd that much and have never paid much attention to it until I started hearing a rattling noise. I am wondering if the shop didnt properly index the electric motor properly on the transfer case when they installed it? The 4wd low function works fine so I am not sure where to start troubleshooting

 

[Ozymandias]

I asked because I wonder if your axles ratio, front rear matches.. maybe someone messed around with it in the past.

But pretty easy to check, make a chalk mark on both driveshafts at the 6 o'clock position and then move the vehicle ONE wheel rotation forward. The marks should still match perfectly after that.
2WD position of course.