3 or 4 speed automatic? Plymouth Gran Voyager 1996

You have a 3 speed O/D and he has a 4 speed O/D. His should shift more than yours but it could just mean your fluid and filter is cleaner or your plugs and injectors are cleaner and it is firing good. Hopefully it doesn't mean anything negative. The Haynes manual is always a good service source of information for a handyman.

You mean his fluid, filter, plug injectors are cleaner? Since it feels liek his car has more power. plugs = spark plugs?

The quicker shifting could be due to the cleaner fuild and filter as well as cleaner spark plugs and fuel injectors giving more power.

Thanks so far :) I've doing some checking. Going to clean the injectors, replace fuel, oil and air filters. Thinking of a high performance air filter (probably one that fits in the box other wise I'll have to create a box for the "wrong" shaped one). Also going to replace the thermostat with a new one, high performance maybe also. Then I'd like to check the fuel pomp. But I guess that replacing fuel filter and cleaning injectors will be sufficient. Going to replace oil and transmission oil with fresh one. Replace coolent also. How could I check or know that the fuel pomp is ok? Is a cooling system on the transmission worth it? Do you have more ideas or tips on how to increase performance?

No need for high performance parts but good OEM parts according to the Haynes Manual. Can't always listen to or beleive the parts counter info from Generic parts stores especially on certain parts such as plugs. Sometimes less expensive plugs will work better than the latest or "greatest"