My father in laws 52 plate Ranger crew cab is very tail happy, the back is always stepping out without warning and it aint his driving style! several people have driven it (its kinda like a pool car) and they all say the same. Its had 2 new leaf springs cos 1 was broken but other than that its only a 3 year old car and hasn't done any hard work really. Any suggestions? All looks normal, nothing bent etc