Many issues to deal with

My 2005 Envoy seems to have a few different issues...

*First, there is a high pitched whine which gets louder when you accelerate. It doesn't sound like a 'belt' whine though, not sure where to even start on this one. We had the oil changed but it did not seem to affect it. Also it seems a bit sluggish.

*Second, the speedometer, works perfect sometimes, other times you get in and the speedometer "starts" on 30 or 40. I have noticed though if you turn the truck off then back on it drops by 10mph each time...so you can reset it but with much effort....is this just a loose cable or my electrical system?

* Possibly related to the speedometer, the truck will not turnover sometimes. Don't think the starter is bad, it's more like maybe the ignition switch. You can turn the key and get nothing sometimes, other times the truck starts normal or will even start after you have turned the key forward and let go (cranks on the release of the key).

*Gas Gauge used to read correctly, now it's kind of sporadic, you may get in the vehicle and have "48 miles then after you go 2 or 3 miles, it drops down to 26 miles, then the fuel light comes on...stop and put $2 in gas and you are up to 50 miles....whats up with that?

Any advice you guys could give me would be greatly appreciated. I just bought my envoy about 4 months ago and so far I Love it, if we could just take care of the glitches.

Also if it helps it is a high mileage vehicle as I drive about 150 miles every day. Has recently began using much more gas. Also all fluids seem to check ok...the power steering fluid gets a bit low at times but no major leakage...also this whine sounds kind of like a power steering whine, but it doesn't seem to be related....there is no noise when turning or steering...just upon acceleration.

No way to really determine the whine without being there, but check the rad fan/clutch for locking up, common issue. On the speedo the usual culprit is the speedo head itself or the stepper motro that drives the speedo, the cluster must come out to fix this, may not be a dyer type repair. The starting issue could be the ign switch, the starter relay or the starter itself, circuit checks must be made when this occurs, I would suggest a factory manual if you attempt these repairs. The gas gauge could be the gage or the tank unit, again the FSM needed to check this out properly.