2000 trooper limited not staying in 1st gear

my trooper is not staying in first gear on take off. If i shift manualy it works just fine. I have no warning lights on(check engin or tranny oil temp or check tranny). when i bought the car it had 98000 miles, i have put 4000 miles on it since. anyone have any ideas? much maholos for any info.

I would check the fluid level (there is no dipstick for it).

what do you mean it is shifting out of first gear? what does it do, go into neutral? or ?
or is it just the gear indicator lights on the dash?

after you check the fluid, and if it is ok, you might want to check two other things
1. the mode switch
2. the alternator

any other symptoms?

//bc