93 ZJ 249 Viscous Coupler

I'm thinking that my viscous coupler is broken... What are some symptoms of a broken viscous coupler? What is the remove and replace procedure with the 249 viscous coupler. Can it have effects on drivability and drivetrain?

 

I found a viscous coupler for an NP 249. They want 50 bucks for it but the mileage is unknown.

 

I'm not familiar with the coupler but is the new replacement expensive?

 

Yeah like $400 expensive

 

I think I found a pretty sweet deal, I haven't talked to the guy about it yet... What do you guys think about this? What questions should I ask him?

 

Price is good but tough to determine whether the parts are as good as described.

 

Is there anything he can do on video and send me? Or is there no way of testing it and I'm just taking a chance?

 

Other than some obvious noise or grinding I don't know whether this could be confirmed as a good one. Buying anything used has some risk or could be lucky or a seller with integrity

"The viscous coupling has two sets of plates inside a sealed housing that is filled with a thick fluid, as shown in below. One set of plates is connected to each output shaft. Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping".