I have a 95 ZJ w/ 4.0. I bought this w/ a bad front axle and never drove it until I changed it. When test driving it there is a bad vibration in reverse gear w/ your foot on the brake, and some clunking noises in forward and reverse when accelerating. Are these syptoms of a bad VC? If not what could it be?
Thanks in advance for any help

 

Can anybody help me?

 

The first things that come to mind for me are transmission & motor mounts. I am not familiar with the VC acronym.

 

Long time lurker, first time posting. I don't own a GC yet, but hope to soon. VC = viscous coupling, referring to a part that frequently wears out in the 249 transfer case. OP, have you checked the u-joints?

 

Does not sound like a bad VC. I agree that it could be engine and or trans mount.

 

isnt the best way to test for a bad VC to drive in 8-figure on a hard surface? If the tires start to jump/make noise then its a bad VC?

 

Check the u-joints. A bad/damaged u-joint can cause vibrations and/or clunking noises.
See if the drive shaft has any damage or may be bent.
Check for any bent or loose wheels.

Yes.

 

I was able to have a friend crawl under the jeep while I shifted from reverse to drive and back. The front driveshaft torques violently a bout a quater inch before the rear ever move. This is produce the clunk sound. Would a bad vc cause this or should I get another case? When you shift the tcase in neutral the vibration goes away. All drive shaft ujoints are new and the cv joints in the axkeshafts are fine. this thing clunks and vibrates without the jeep even moving. when you shift from park to reverse or from neutral to drive

 

That could be from play in the front ring and pinion gears. The front shaft shouldn't move that much with the front tires stationary, since you state all the u-joints are in good shape.
I'd pull the cover off the front diff and inspect the gears, or take it in and have it done. Have a drain pan ready to catch the fluid that will come out. Look for any damage, loose parts, or debris in there as well.

 

I purchased the front axle assembly form the local junkyard. I had everything gone though with it when we verified the gear ratio was the same. There is nothing wrong with the front axle assembly. When the shaft lurches like that it does try to turn the front wheels. I had the ebrake on and my foot on the brakes while doing the check as stated in my last reply.

 

It really does sound like backlash in your front ring and pinion gear. If your front end clearances were all correct the driveshaft wouldn't move at all no matter what was happening in the tcase. That's not an uncommon problem with 249 equipped grands, the d30 r&p has a hard time handling the constant torque.
To check you can drop the driveshaft and turn the yoke back and forth, that will show you how much play there is in the gears.

 

Agreed. Leave the 4wd locked in, remove the front shaft. Check the joints on each end of the shaft, and check the pinion o nthe axle for excessive play in/out, up/down and rotationally. It's not likely it's in the transfer case. To verify that, you can check the front yoke on the transfer case with the shaft out as well.