Can someone please tell me why does a faulty throttle bady throws up so many different codes Gear box faults etc ?

 

You'll need to post the codes. What makes you think the throttle body is bad? Based on what I've seen on this forum I'd say you need to start with verifying your battery's in good condition. Get it load-tested and also check the cables for corrosion. Air leaks downstream of the MAF sensor also are a common gripe. Post the codes you're getting.