Go to both of these pages, print out the diagrams for reference
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt
There is a grease zerk on both of the steering pins ( # 5 & # 6 )which are retained by a circlip.
Pull the clips and inspect the pins.
If they are badly worn, replace them
if not clean & regrease them with the wheels off the ground so the grease gets to the places that normally have weight on them.
The wheels have a non adjustable tie rod between them. ( # 10 )
Check that you have about 1/2" toe in between the front wheels.
If not remove the tie rod and bend it to shorten the tie rod or replace it
The steering shaft ( # 9 ) has 2 bushes (# 8 & # 10 )these get lubed with a dry lubricant like spray on white Lithium grease ( auto parts store ).
Check they are both round and not flogged out oval if so replace them, a small amount of wear makes a massive difference to the contact between the gear on the shaft (# 9 ) and the fan gear ( # 11 )
Both of these will benefit from some spray grease regularly as well
The teeth on both gears wear and that makes the steering very heavy, but start with the clean & grease first.
Because of the geometry the steer gear it is a lot easier to steer when going backwards and if it has no diff will turn a lot tighter going backwards as well so 3 point turns will be lot easier than foreward turns.
I resell a lot of local mowers which have solid axels and once the customers get used to "backwards" steering they love them and mow around trees & poles backwards