2002 SWB Transit 2.4 TD starter problems

[scooobi]

Hey everyone I need help with a problem i got with my van. I have a 02 2.4L turbo diesel 5sd auto transit and just recently the starter motor failed and had to be replaced. The drive shaft inside it had completely snapped in two.. anyways i ordered a new one from the uk that was supposed to be for my model.. after fitting it for some reason there was a bolt left over and we couldnt figure out where it went. Everything was fitted securely and the 2 wires where connected back up and it seemed to be ok. Occasionally now when i try to start it the motor will crank for a bit then makes a loud thud noise that shakes the van and cuts out. When this happens it can take 5 or 6 attempts to get the engine to fire.

Is this because i have the wrong starter motor or is something else wrong??? Any help is muchly appreciated im starting to get desperate lol