My 1998 Navigator seems to vibrate/sputter a little as the gears are shifting. on 1998 Lincoln Navigator

This seems to occur when I am driving at speeds of 40-45 miles per hour. What could be the problem?

Asked by for the 1998 Lincoln Navigator
scan codes and post so we can adv
2 more answers , 3 more comments
scan codes and post so we can adv
when is the last time it's had a simple trans service( not flush) , just drain & fill &filter if needed? With FACTORY fluid.
Hmmnn... good question and never thought about that...I think it's been a long time since I have had the transmission fluid drained and the filter changed. May need to do that since I have 198,000 miles on it!
Don't flush it! Just a drain & fill as I previously mentioned. Good luck.
ok many thanks again for your help!