1990 Ford F250 C6 Transmission is a little soft on take off in drive?

I have bought a 1990 Ford F250 Custom, that was damaged in the last ice storm, great truck, it is a little slow on take off in drive.
I can shift the leaver down to-D1- & it will take off as it should.
I'm thinking of droping the trans. Pan & changing the filter, which has probably never been done.

D1 truck starts out in a lower gear. When in D it starts out in like second and in D1 it well start out in first. I had a 64 Gal. That was the same way. If it took off in D it would start out in second and when I shifted it to D1 it would start out in first.

Before doing the change find local shop at ATRA.COM for free road test to determine if it is a internal problem. Don't want to waste money if the transmission has to come out

Sounds like the governor is sticking causing the truck to start in 2nd gear. Let your local transmission shop folks do that fluid and filter change and be sure to tell them about the slow acceleration. They can correct this problem easy.