What Custer did in 1874 and 1876 that put him on grant's blacklist?

Custer worked with those in charge of the impeachment process of the president. Grant was also under some pressure for his behavior towards Custer, and there was a climate of concern, which he feared would be compromised if the campaign was not headed by him. In the same way, Grant could be blamed for ignoring the advice of Custer's superiors, so he had few options other than indulgence.