Hi Andre’
If your truck is indeed a T18, I believe that is what is referred to over here as a “granny gear” 4 speed. What this means is that 1st has a very low ratio and is not intended for everyday use. 1st is intended for heavy pulling only and 2-4 are more suited to everyday use.
As long as it hasn’t been modified you shouldn’t have any problem starting off in second as that is the way it is intended.
Go ahead and post some pictures for us of the data plate, transmission and rear end and lets figure out what is going on. Throw in some of the whole truck too. We like pictures.
I’d suggest posting the data plate and a more detailed question and description of the issue in the drive train section, you will get more help there.
Do you know what engine you have?