4wd bent drive shaft?

['89 BII blue thunder]

i have a '89 bronco 2. it drives fine when in 2 wheel drive but whn 4 wheel drive is engaged, the steering wheel jerks back and forth as you drive. is this because of a bent drive shaft? is it normal? any ideas would help

thx

 

[stegomon]

you have a bad u joint in the front....take the bad axil out and change the ujoint...slap it back in and call it a day