I have a 1989 Chevy S-10 Blazer Tahoe. The transmission won't shift out of Park and feels like it is jammed in park. I have changed the linkage and checked my transmission fluid and everything is good. It will Roll in 4 wheel drive Neutral. Any Ideas on What would be causing the Transmission to be jammed????

 

1st thing I would look at is the linkage that allows it out of park. Depending if it column or console. I don't know if an '89 had a brake safety switch (doubt it actually) but in my '02 I have to apply the brake for it to shift out of park.

In 4wd neutral it's dissengaging the transfer case to the front & back. That sounds like the culprit. What may have gotten over looked when replacing the trans linkage?

 

I'd drop the pan off the bottom of the transmission (good time to do a filter change) - look to where the linkages enter the side of the transmission (this assumes everything outside checks out) - if its a mechanical problem inside you 'should' be able to see it - I say should because there is a component covering the cog that actually sets the park brake, but the rest of the linkages are fairly visible - if its the detent spring (part that makes the click-click noise when you select a gear) then it'll be front and center right where the linkages go through the wall

googled up a PIC - you want to look at the only thing in this pic that DOESNT have an arrow pointing at it, right along the top of the image (left is the engine)

I'd have a look at anything mechanical in that area and see if you can see something jamming - get a filter kit, it should come with a gasket for the pan - one thing i was cautioned on when changing a filter: unless its damaged, leave the seal for the filter neck alone. More damage can and has been done to the casting by people going after that seal - both when they needed to, but more often when they diddn't need to.