If adjusting the servo horn or adjusting the trim doesn't work then you may have bad servo. If it is the original 23 year old one then you are probably due to replace it anyhow. While you are at it, you can do a few inexpensive mods to the truck that will make it far more reliable and fun to use.
These would include:
1) replacing the MSC with an ESC -not too expensive to do and improves everything greatly. I am selling a super rooster ESC that would do the trick & it would make the truck more plug and play. Here is the link to my ad:
http://www.rcmt.biz/bd/showthread.php?t=14582
2) replacing all the bushings with proper bearings. Again, easy to do and you can get bearing kits super cheap from e-bay. This will improve your Clod in a really big way.
3) swap out all your steering links with proper thicker aluminum ones. This will remove a lot of the slop in the steering and make it more fun to drive.
4) cut/shave the stops on the top and bottom of the wheel hubs off-it is free mod and it will allow your wheels to turn more making it easier to turn
Hope this helps. Oh and post some

ics of your Clod...always nice to see another member's truck! :tong