My 54' 88 with p/s makes a whistling noise while going straight. It goes away when turning. Any ideas? Rebuild the steering box? Seals?

 

That seems unusual. Most of the time the noise is when you are turning. Call Chip at Power Steering Services Inc. He is a great guy and lots of people on here have used him and I have never heard a complaint. He rebuilt the sector on my 54 and it is perfect. The shaft on the 54 comes out of the sector and goes all the way up to the steering wheel. I had to build a crate to ship it in and the freight was about $75 each way. Here is his link:
http://www.powersteering.com/us/