95 Jimmy squeel or whine when idle

I have 95 Jimmy w/ 128K miles on it. There is a high pitched whine coming from under the car near possibly near the transfer case. The pitch is always the same just gets a little faster when I begin to accelerate and is undetectable when above 2000 RPM. It sounds kinda like a car alarm. It happens intermittently once the car is warmed up especially after being on a highway. Its not the brakes because it happens at a complete stop. I already had the Catalytic Converter and the CPI module replaced.

My supects are:
*transfer case
*transmission
*fuel pump (i know its in the tank but just the fact that the noise is constant)

Any ideas? I have searched all threads and other forums but no sign of a similar problem.

Ok I'm doing some more reading an really thinking that the vacuum lines to the tranfer case have something to do with my situation. Can anyone provide a VACUUM HOSE DIAGRAM FOR THE TRANSFER CASE?

I'm thinking one of my hoses might me unattached or attached incorrectly. How can I test this system?

The manual I have sucks: it covers 87-95 S15's and barely touches on the 95 models which was a completely different generation!

I plan on having my Jimmy until at least 200K miles and there is no doubt that the engine can make it but these other little quirks are killin me.

Is it a 95, with the CPI, engine code W? If it is, you can disconnect the vaccuum line connected on the back of the plenum, by the distributer and see if the sound goes away. Cap the vaccuum line and take it for a drive. If the sound is not there, then you have narrowed it down to a vaccuum line. If its still there, then not vaccuum. Don't forget to reconnect it as this line controls not only transfer case vaccum lines, but also the HVAC controls, among other things.

If it's a squeal, more than likely it's the belt or the tensioner pully...

Is it a 95, with the CPI, engine code W? If it is, you can disconnect the vaccuum line connected on the back of the plenum, by the distributer and see if the sound goes away. Cap the vaccuum line and take it for a drive. If the sound is not there, then you have narrowed it down to a vaccuum line. If its still there, then not vaccuum. Don't forget to reconnect it as this line controls not only transfer case vaccum lines, but also the HVAC controls, among other things.

I disconnected it and taped it and the sqeal still comes back. And it isn't a belt- you can't hear it too much with the hood open but when you put your ear behind the drivers side front tire it is very loud.

Have you ever serviced your tranny or transfer cases in 10 years?