Example 1
Jason: Mike told me he would join the football team.
Example 2
Jason: Mike told me he was going to join the football team.
"will" and "is going to" in a reported speech often become "would" and "was/were going to."
Are they different?
Does "was/were going to" imply Mike did not actually join later?
Or
None of the usages implies Mike later really joined or will join?
There is no definitive conclusion from either statement alone. You'd have to follow up with a statement covering whether or not he did join.
In speech, emphasis on 'would' or 'was' would hint towards him not joining, but you'd still expect a concluding statement to be certain.
Jason: Mike told me he would join the football team, if they'll accept him.
Jason: Mike told me he was going to join the football team, but later changed his mind.
Each just states intent, not result.
