Transfer Case Vibration

[Torque Junkie]

Has anyone had any expereince like this and if so how did you eliminate it?

 

My '79 has an NP-203 Chain-Driven transfer case converted to part time w/ manual hubs.  With the hubs locked in and the lever in "High" (2wd) I have no vibration at all.... as soon as I put it into "High Lock" (lock the transfer case into 4WD) and put power to it i get some pretty significant vibration and noise that shakes the whole truck, but I can feel especially through the tranfer case shift lever. It also feels like it's bogging down and stealing lots of power from the truck.  It does the same thing in "Low Lock".  It also only does it when accelerating, moderately at lower speeds or lightly at higer speeds.  It doesn't do it while coasting or anything.  Or are the 203's just naturally really rough, noisy transfer cases??

 

The lever also has enough play in it to where after it's in lock (high or low) for 10 seconds or so it wiggles out enough for the "4 Wheel Drive" light on the dash to come out.  What would cause this, any ideas?

 

Thanks for any input!!

 

-Mike

[Guest Friz]

Check the front u-joints and driveshaft for any problems like missing balance weights and the like.

Also try and dertermine if it's the xfer or front end. Drive with the hubs locked but in 2wd, then put it in 4wd and unlock the hubs.

[Torque Junkie]

OK, I ran some tests and discovered that the vibration/noise only happens when the hubs are locked and it's in 4wd.  It doesn't do it at all w/ the TC in 4lock but the hubs unlocked, nor does it do it with the hubs in but the TC out.  I just had the front axle U-joints replaced not to long ago....  I wonder if it's in teh front drive shaft somewhere/how?

 

Could it possibly be as simple as a transfer case oil change?

 

It basicly only does it when the entire front end is under acceleration load

 

-Mike

[Guest Friz]

It's possible that the u-joints weren't installed correctly. I've seen "good" mechanics beat them into place with a hammer! or maybe they weren't greased right.

Could also be a  pinion bearing or gear problem. Any fluid around the yoke? Also check for play in the pinion shaft.