'98 Cummins, won't downshift to 1st

A few weeks ago I bought this '98 automatic. I love the truck, but an annoying problem keeps popping up. The truck normally shifts fine, but once in a while it will not shift into 1st gear at a stop. If I manually kick it down to 1st it will usually cooperate and upshift ok, but typically the symptom continues at least until I shut off the truck and start it again. Other times even if I put it in 1st gear it still refuses to shift lower than 2nd. Tonight coming home from work it kept starting out in 3rd gear! If I shifted down manually it would go to 2nd, but not 1st.
This problem might occur a couple days in a row, or it might work fine for 3 or 4 days. Is my tranny on the way out or is there a likely fix that won't cost me a couple grand?

Go to dieselbombers.com and join and start asking questions they will know because theres dodge gmcs chevys ford and others but they will know.

Thanks for the information; I'll check it out.

A few weeks ago I bought this '98 automatic. I love the truck, but an annoying problem keeps popping up. The truck normally shifts fine, but once in a while it will not shift into 1st gear at a stop. If I manually kick it down to 1st it will usually cooperate and upshift ok, but typically the symptom continues at least until I shut off the truck and start it again. Other times even if I put it in 1st gear it still refuses to shift lower than 2nd. Tonight coming home from work it kept starting out in 3rd gear! If I shifted down manually it would go to 2nd, but not 1st.
This problem might occur a couple days in a row, or it might work fine for 3 or 4 days. Is my tranny on the way out or is there a likely fix that won't cost me a couple grand?

My 97 does the same thing, I just changed the speed sensor but it didn't fix that problem, maybe a shift solinoid?