getting into replacing a 242 (97 grand cherokee). the guy just driving down the highway in 2wd and said it just made a loud noise and jerked a couple times. i found the case cracked and i pulled the unit apart. the chain jumped off the front drive sprocket. any idea as what may have caused it? i'm thinking that it may be due to a tire issue. fronts are goodyear rears are daytons same size but i measured circumference and found 1" difference. i'm thinking this was the cause of the failure but with it in 2wd i'm not sure. any opinions?

 

Only way the size of tires could cause this failure is if it was in part time 4wd.

How many miles? Sounds like it may have been a stretched chain and it was finally fatigued enough that it jump and caused the damage. 242's are also known for just randomly grenading when they get up there in miles. Put a new case in and you should be golden.