A/T stutter in fourth gear

[engineer73]

I have looked for this in many fourms and came up with nothing. The issue that I am having is between 45 and 55 mph the trans. is in fourth gear if I give it any gas or go up an incline it sort of studders before it will downshift almost like driving a 5 speed in 5th gear at 35mph and giving it some gas. Not sure if that scenario helps. I was just wondering if that was normal or a little odd.
I have only had this car for just over 1 month and since then I have changed all of the fluids in everything except the trans fluid. Replaced the timing & balance shaft belts all accessory belts all of the filters did a compression and leak down test and everything is great. I was just wondering if there was anything that I may have overlooked before I start doing some mods.
Thanks in advance
also thanks for this great web site,

 

[inneedof]

how much power are you making? forth is overdrive to to much power will overwhelm it easily.

 

[engineer73]

It is all stock.

 

[engineer73]

Anyone have any idea on this.

 

[DSM4me44]

What rpms are you at when it stutters? When does it stop stuttering?

 

[rich3389]

Boost leak test.