Only a handful of shows never jumped, and Barney Miller is one of them. That's quite a distinction, yet I'm not surprised. It's one of the best shows in television history.
On the far left of the JTS website, at the bottom, click on Never Jumped.
http://www.jumptheshark.com/

that is a really fun site to visit. I went through the happy days part a long time ago and was almost in tears i was laughing so hard. I believe wkrp never jumped the shark either; thats my other favorite 70's show!

Levit and Herb Tarlek sometimes shared clothes.

I also don't think Barney Miller ever jumped. It could *easily* have gone downhill after they lost Abe Vigoda and Jack Soo, but it never did. Just goes to show how great all the characters were and what great writers they had.