can vacuum leak cause automatic transmission to downshift?

[jeepster]

My automatic suddenly began misbehaving. It won't shift 2 to 3 until 60 km/h even with gentle acceleration. This is on level road with no passenger or cargo added.
RPM much higher than normal, never seems to reach 4th gear. At least I don't hear any klunks, rattles, buzzing or other worrying sounds.
I had a major service a month ago, and they changed the ATF and filter. I checked the level, and it is okay. I get no PCM error codes. The economy-power switch is working.
I can't see any hoses or wires come off under the hood. Also the engine temperature seems a bit higher than normal. I know some cars use intake manifold pressure as one of the factors to decide if engine is under load - does the Commodore?

[mcroger]

Sounds like the one of the clutches has gone for me.

[nathanshnoz]

my auto i just replaced did very similar things. does the fluid seem dark in colour? does it smell? i'd say the bands in your auto are on the way out.

[jesse_lankey]

id be putting my money on the throttle position sensor, even more so if you have a vacuum leak and it would explain high RPM aswel

[Jaymz]

my auto i just replaced did very similar things. does the fluid seem dark in colour? does it smell? i'd say the bands in your auto are on the way out.

^This happened to my trans as well. Fluid was a horrid brown colour and smelt BAD. Had been an issue for awhile. You will also notice your fuel economy will be horrible now too.