l have a 2007 Subaru 2.5i. It is an automatic 4 speed, when l accelerate normally l rev to about 3k rpm from first to fourth gear. And a few tims a day l hit 4-5k rpm in the first 2 gears.

Will doing this cause problems to my transmission or engine, and when should l expect to see these problems.

Going 4-5k RPM, even to red line every once in awhile wo not do any harm. The lower amount of revs, the lower amount of wear and tear on the engine and tranny. Just do not floor it every single time.

No it won't, just try not to rev over the red line and not to low.