Front Wheels locking in reverse

[BrianReally98]

Hello forum!! A friend of mine has a 2000 GMC Yukon 4wd. She said her truck was jumping in reverse so I went over to take a look. When the truck is in revers and starts back out, both wheels/tires act as if they're locking up. They lock & release, lock and release, and so on while the truck is moving backwards. It only does this in reverse. I'm assuming there is an issue in the front differential. HAs anyone else experienced something like this? Any insight would be awesome...She doesn't have much money to spend, and i'd like to help her out, but i feel like i'm going in blind. I do not have a lot of experience with 4WD. Thanks again

 

[Gzes]

might need to get the front dif redone or might be the transfercase