Jeep Grand Cherokee 3.1 Limited has no strength

Good,
I bought a Jeep Grand Cherokee 3.1 limited to which I have changed the automatic gearbox for one that I know that worked more or less well.
The thing is that after the work done I notice the Jeep that has no strength, it is like the engine does not respond well. Above all, it is noted that it has no strength in slopes and in Llano does not have a strong acceleration, I also realize that it makes the changes of march very soon as at 2000 rpm
the thing is that in the picture it does not indicate any failure.
Can the engine be in security mode for a problem and not indicate in the picture?
I would appreciate if someone could give me some clues of where I can start solving the problem.
Thanks in advance