Hi guys,
I have a grinding noise in my drivetrain and I think I've narrowed it down to a bad transfer case (NP231), but I'd like to see if anyone has had the same issue before I pull it. I get an intermittent, but more often than not grinding noise in 2WD. First I thought I had a bad right front wheel bearing/hub, so I changed it, but the grinding noise was still there. I checked all of the u-joints, and they're all relatively new, and good. I began searching the forums and was convinced that the snap ring on my output shaft was toast, so I pulled the driveshaft, and the ring is in place. The reason I think it's the transfer case and not something else in the drivetrain is because I can make the noise go away (for the most part) by pulling the transfer case shifter towards 4H while driving. Perhaps one of the internal bearings is shot?

 

I had a similar issue at one point with that kind of noise and it ended up being the 4WD shifter on my '96 Ram 2500 4x4. The plastic detent at the top of the shifter had come loose and allowed the shifter to not position itself correctly while in 2WD. Once I fixed up the shifter and linkage issue, the issue was resolved. I could shift into all modes (2WD and 4WD) properly once I addressed fixing the shifter.

 

What year is it? I'm feeling a weird buzz in the drivetrain for years. Thinking it might be the xfer case as well.

 

I had the same type of sound a few years ago, It ended up being the large roller bearing inside the overdrive unit, which means the overdrive unit would need to be removed and remove the direct clutch assy.

 

Ugh. How could you tell it was the overdrive unit and not the transfer case? One other clue: when I stop the truck and start up again, the noise will usually stop for a little bit. Quite often, when I hit a bump it starts up again. It could indeed be a worn bearing

 

I would check your transfer case shifter closely to ensure that the shifter adjustment isn't the issue, since you stated that you can resolve the noise issue by moving the shifter a bit. What year is your truck?

 

I'll definitely check the the shifter before I pull the transfer case

 

When my transfer case went bad anything above 25mph it would grind like trying to shift into 4x4….take off front driveshaft and see if it still makes noise, and check the transfer case fluid, they don’t hold a lot so a bad output shaft seal could drain fluid pretty quick. Just saw it on a f350 at the shop I work at. Full service last winter including transfer case flush, last week no fluid/ bad output shaft seal and leaked ALL of it out in turn trashed transfer case and made some bad noises

 

Have you checked the fluid in the transfer case?

 

I had a tech replace the transfer case assy and the sound was still there. I'm only sharing information that I have seen. Have you checked the fluid level, U-joints and pinion nut at the rear differential?