Hilchos Lashon Hara chapter 8, section 10

We will now discuss before whom it is forbidden to speak lashon hara. It makes no difference whether one speaks to other people, relatives or non-relatives, or to his wife, unless he needs to inform her of something for a future benefit such as if she is lending to evil people and it will be difficult to get payment from them afterwards. Therefore, he tells her their bad nature and warns her not to lend them. The same applies if a partner tells his partner of people he considers dishonest, and suchlike. (This is similar to what they said in Kiddushin 52b: Let the disciples of Rabbi Meir not enter here because they are quarrelsome, etc.”).
Even if one does not know of their bad nature personally but only heard of them, he may also tell her what he heard of them and warn her regarding the future. Although she not absolutely believe what he heard of them, nonetheless she may suspect. (However, in this case he should not tell her in a way that indicates he believes what he heard. Rather he should say to her: I heard such and such about so and so, so be careful not to lend him). Besides this there is no difference in the matter.
(Many err in this and matter and tell their wives all that a person in the beis midrash or market did to them. Besides the lashon hara involved, he also increases controversy because she will certainly bear a grudge and quarrel with the person or with his family. She will also incite him to quarrel with the person and in the end she will insult the person herself. Therefore one must be careful not to tell one’s wife of such matters).