I have a 88 4Runner SR5 V6. I just put in 4.88 gears into my rig with 33x12.5 tires and am having a serious problem. In 2Hi the truck drives great (as expected) but in 4Hi/4Lo the truck has brutal movement on the front end. Essentially the when in 4WD the steering wheel vibrates and shimmys back and forth. Before the gear installation there was no issues but does any one know what would cause this problem?

If I remember right if your rig came stock with 33" tire they had 4.56 gears. Or do you mean ya regeared both front and rear? If so I would look really good at your cv joints ya may have pulled them too far and poped a ball bearing out or some thing along those lines