94 voyager gears dragging out engine

I just bought this 94 voyager and the guy I got it from had just put in a used tranny. When I drive, the gears do not change until the maximum speed has been reached, which means the engine is revving very high before it changes gears (it upshifts very late). Is there any way to adjust or lower the speed/engine rev at which the gears change?? It changes from first to second at 40 km/h and second to third at 60 km/h.
Also, when the gears change, they do so with a jolt or like one part is slamming into another. There is no grinding of the gears, just this bang when it goes back into gear.

What eng? 3 0r 4 speed?

3.0L engine and 3 speed tranny.

Could be a couple different things.Since the trans was swapped you first want to make sure they put the throttle pressure linkage back in place an that it is moving freely. Ck to see if there is a metal rod that connects the throttle body with the trans. If it is in place then you want to move the throttle to full open at the throttle body and seeif thelinkage moves freely and returns forward when the throttle is released. Try the and see what you come uo with.

The linkage is in place and it moves freely. Does it need to be adjusted?? There is a screw on the connection to the trans that can be loosened to adjust the length of the metal rod.

Yes that is where you adjust it. To shift earlier you need to shorten the rod. Also ck at the throttle body and make sure all the slack is being taken up. There should be a spring at that end holding the linkage snug to the stud. A flat piece with a slot. In other words if you move the lever at the trans as far to the right as you can and release it; it should spring back on it's own. Sorry hard to describe.

OK I think I got it. Took a few tries to get it to the right length, but now the gears are shifting at the right speed.
Thanks for your help!