My Blazer is one where the front drive shaft is always turning…. My transfer case has 4L / N / 4H. Basically I run around daily in 4H… then when I need 4x4, I simply put the truck in neutral , lock the hubs and it’s engaged.

My Question is when I’m running around in normal 4H with the front HUBs unlocked - If I get into an uneven mud hole ( where one side the tire is real low… the other side it’s jammed up into the frame) The truck starts making a bad grinding sound from the transfer case … this is without me doing anything, not touching the transfer case.

It’s make that sounds like when you shift the transfer case ( in a normal truck) from 2H to 4H … you get that quick “grind” sometimes. Kinda hard to explain… but when I get into an uneven mud hole… it makes this sound constantly.

I just got the front drive shaft completely rebuilt and it’s bullet proof. Maybe is it not lining up correct - transfer case to front differential ? And this causes the sound when the front and back is uneven due to uneven holes? My truck is lifted about 6+ inches.

 

Are you sure you are not somehow hitting something with either driveshaft when flexed out? Does it make the same noise if you alternate the wheel that is flexed up into the chassis? Does the noise sound like it is coming from inside the transfer case or somewhere external?

 

check to make sure your driveshafts arent hitting the crossmembers. see if theres any scrapes or shinny parts. i believe with i lifted one of my blazers in the past i had to notch the crossmember cause of the same deal


edit... lol he beat me to it

 

Don’t think the drive shaft is hitting anything.. but yes I should and will check the crossmembers.

“Does it make the same noise if you alternate the wheel that is flexed up into the chassis?”
I don’t know.. but I can test it buy driving into this one particular mud hole in the opposite direction. ..that will tell me… great idea.

“”Does the noise sound like it is coming from inside the transfer case or somewhere external?””

Sounds like it’s coming from inside the transfer case… it’s like the alignment of the shaft get’s messed up when the tires are flexed into different directions. When it starts, it’s constant… I can move the transfer case from N back to 4H…no change. I can also move the transmission from D to N and no change.


As stated above, I could be bottoming out the drive shaft onto the ground. When the front tires drop down into this one on hole ( a steep narrow hole) .. the drive shaft could be bottoming out on the dirt causing it to push upward ( getting out of alignment) thus making the sound? Don’t know … keep in mind this drive shaft is a new rebuild… real solid, no play at all in it.

Thanks, those are good ideas and suggestions… I will check into them…let me know if you have more.

 

Wait a minute here... The noise does not change if you put the transmission into neutral and rev the engine?? If so, it has nothing to do with the transfer case or driveshafts...

 

Correct... but I know 100% the clunking /grinding sound is the transfer case. Remember, my front drive shaft always turns regardless ( not sure If this is case with all older Blazers) ... I have 4H and 4L... no 2H. If the truck is moving… the front drive shaft moves.

After thinking - the best way to describe the sound is - When you ( on your normal 4x4) sometimes are in 4H…and you slowly..real slowly pull the transfer case into 4L. If you do it slowly ( instead of a short fast shift) it will sometimes make that clunking/grinding sound. That’s the sound I get when the tires flex in different directions in the mud hole….. but the sound is content.

Maybe the transfer case is popping halfway into Neutral when the tires flex …

 

I have the fulltime NP203 in my 74 so I know how they operate, but your assessment is flawed. The driveshaft will not turn when the transfer case is in neutral and nothing in the transfer case will turn when the transmission is in neutral. So if the sound persists when the transmission is in neutral, then the problem is not with the transfer case or driveshaft as I have stated.

 

maybe your clutch or ....... slipped my tounge, its no fully engaging and disgaging and is grinding away should check that out wouldnt hurt

and i know this is out of question but how do you create the cool name logo?