New to me 1999 4x4

[firedog]

I am going to pick up this truck Wednesday evening. It is a 1999 chevy 4x4, what I have learned about it is it has a 2004 HD front clip, 5" lift and 37" tires with 20" wheels. Zero rust, none at all, which is why I jumped on the chance to purchase it. You just don't see these trucks with out the rockers gone. The truck has the 5.3 and the odometer shows over 200k. the interior is clean bucket seats and all power. No engine lights on currently. The bad the transmission will not shift into 3rd or 4th. The tranny was rebuilt 30k miles ago in Texas. So Wednesday I will go with my neighbor and load it up on his trailer and bring it the hour home. I have been searching for a 4x4 chevy truck preferably with a lift and something not abused. Craigslist and FB marketplace is full of 250k mile rust buckets with issues for $3000-$5000 so I hope this turns out to be a good find. I feel I got a great price at $1700.


Any suggestions on where to look first with the transmission? Or do I just pull it and replace it?