I need to replace/repair my son's 99 Grand Cherokee rear (grinds so bad even I'm afraid to ride in it!!). All the parts and junkyards are asking if it is a "spicer 3.5", a " quadra" etc. How can I find out which rear end is in the jeep? All the pictures I see have drun brakes, this has disc brakes.

They are asking whether it is a QUADR-DRIVE rear end or SPICER/DANA 35 rear end.

It should be stamped in one of the corners of the differential (pumpkin).

Most likely it is a dana 35. If it was QUADRA-DRIVE it would say QUADRA-DRIVE by the transfer case shifter inside the jeep (COMMAND-TRAC, QUADRA-TRAC, SELECT-TRAC or QUADRA-DRIVE)