Trying to identify book with space travel via gates

[Enjee]

I'm looking for a paperback book I read prior to 1975, I believe.
The protagonist travels to other planets via the ancient "gates", which were built long ago by unknown beings. It is risky because one doesn't know where they will end up.

One scene I remember: On one planet there are machines that let you transfer your mind to another body. Sometimes people are kidnapped from the street and forced to trade bodies. A wanted criminal trades with a terminally ill person, knowing he will then grab a healthy person and force a trade later. The machine has also been used to trade a female body for a male body.

I was a teen when I read this, and this was the first time I had read about a male wishing to be a female, although that bit was a side mention and not the crux of the story.

Also, the protagonist wore a hooded cape.

Note: this is absolutely not stargate.

[Cheryl]

Searching the Internet Spec Fic database by 'portal' -> t="tag" got me several hits, including this list:
http://www.isfdb.org/cgi-bin/tag.cgi?...

[Jen]

The beginning of your descriptions sounds like Gateway by Frederik Pohl. They do travel by gates created by an ancient species and they have no idea where the gates will go.

The rest does not sound like this story, but it is a series so its possible some of this comes into play later (?)

Good luck!