You should be getting about 70mph at 3000 rpm. Sounds like you are not getting 4th or overdrive. These trannys normally start in second gear so you will feel the 2->3 shift and the 3->4 shift. You may be in need of an adjustment to correct this problem. If you are only feeling 1 gear change then you are not getting high. If you are feeling 2, then you may be starting in first but not getting high. Could be as simple as linkage, vacuum modulator or could involve something stuck in the valve body. The 300E is the best,, if you take care of them..

__________________
Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.