I run the plastic diff hub with 5.5t motor,no probs so far,spur gear has worn though (its noisy)so im fitting a new one of those.Just as apoint of interest,when we (my son And I) had the diff axle first,we stripped them to make sure they were greased ect before use and Phils had two conical washers and mine has only one,I never have asked what should be in there,they both work ok
