He said it was clear the party was succeeding in "making changes" to the authority's ruling Labour group, which has been dogged by allegations of corruption and misconduct since the 2016 publication of the Wragge report.
It comes after six councillors quit Labour ahead of next week's local elections.
They include former leader Councillor Yvonne Davies, who said the party lacked "all moral authority", and Councillor John Edwards, who said Sir Keir was "more in tune with the Tories than with traditional Labour".
Labour leader Sir Keir was in the Black Country on Monday to support Liam Byrne as candidate for West Midlands Mayor.
Asked about his pledge made last year to change the culture in Sandwell, he said: "We are making changes, and some of those changes are obvious in terms of some of the people who are now not in positions that they were.
"More, or equally importantly, the group of candidates we have got going forward into these elections are an excellent, diverse group of candidates.
"I'm really pleased to be able to field a team like that, so where we had to do work we are doing work."
Asked about the resignations that had marred the lead up to elections in the borough, Sir Keir said: "I'm very concerned that the Labour Party rebuilds trust and reconnects with the voters.
"I want a Labour Party that faces the country, faces the West Midlands. That's the work that I am doing and that Liam Byrne is doing, particularly among people who used to vote for us and don't anymore.
"For that you need to use your ears and that's what we're doing."
Sir Keir visited Sandwell College in West Bromwich, where he toured facilities and chatted with staff and students.