Buff, most 2wd cossies suffer from piston slap. its to do with the design of the gudgeon pin on 2wd pistons. It doesnt say what pistons is in there but you've got to assume its the 2wd variety. 4x4 pistons use a an offset gudgeon pin and hence no slap. Doesnt mean it needs a rebuild unless there is something else wrong

im sure if the above is wrong i will be told