Originally Posted by AtomicDog

The shift rod should start from the outside of the steering column under the hood. Follow the rod(s) until you see a metal block with a bolt threaded into it's side. The block/bolt on the long rod is your adjuster. Loosen the bolt and make adjustments to the shifter rod, then re-tighten the bolt. Next, try shifting so that all gears can be shifted into. To be fully safe when doing this, I usually jack the truck up and put it on jackstands under the front and rear axles.

Originally Posted by Thomas bridges

This is the linkage that needs adjusted

Originally Posted by master tech

Set the park brake and block the wheels. Get under the truck and see if you have debris stopping the lever from going into park. If there is no debris. Then remove either the cable or shift rod from the lever. Move the transmission lever by hand and see if the transmission will go into park. If you need to make an adjustment, That is under the floor board and either takes a 1/2 or 9/16 wrench to loose. Or 13mm or 14mm..

Originally Posted by HeyYou

So far as I know, there isn't a brake/trans interlock on these trucks..... (at least, up to early 98......)

The linkage is out of adjustment, or, something is blocking/binding.