Can I avoid capital gains on the sale of a rental property by putting the gains into an existing rental property? (e.g. pay off mortgage, repairs, etc.)?

[rlwremo42]

I have multiple rental properties, all with mortgages. I know I've seen articles saying if I sell a rental I can avoid capital gains by purchasing a new rental property. 

But what about existing ones? Can I avoid capital gains by taking the 'gain' amount and say putting it towards the mortgage of one or more existing rental properties?  I've not found any mention of that anywhere.

[MinhT1]

You can defer the taxation of your capital gains by doing a 1031 exchange, i.e, by buying a like-kind property.

But you cannot "invest" the capital gains in existing properties to avoid paying tax on the capital gains.

[rlwremo42]

Thank you for the answer. 

As with many things in the tax code, it doesn't make sense that there is a difference, but I appreciate your quick reply in answering my question.