There could be corrosion in the terminal to the starter. Worth a try to just replace the connection for a couple $$. Mine I was able to just clean a little bit and it works fine but maybe yours has a lot of buildup inside; so even with a new starter (clean on the solenoid side) it can't put the current through.
-Sold 3/13. Replaced by 2010 VW Jetta 2.5-
2005 WK 3.7L Laredo. RC 2", 265 70 17 Bridgestone Dueler Revo 2's. Class III OEM hitch added. Bilstein Struts. Monroe Load Levelers (58643).
Blue WK Club Member #32