I believe your transmission is ready to go into LIMP MODE, with your year that could be 3rd or 4th, i forget which
i wouldn't guess at the cause for the speedometer acting up
P0720 Dodge Description
The speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. The pulse signal is sent to the Transmission Control Module (TCM) which converts it into vehicle speed.
Read more: http://engine-codes.com/p0720_dodge.html#ixzz2oFKRlEKc
2009 Ram 1500 SLT QC, HEMI , 3.55 axle, Bushwacker flares, soft tonneau, Line_X, DEBO Step, Mag-Hytec, Weathertech mats
2016 Ram 3.0 diesel 3.55 w/LSD, G2 tonneau, Line-X, Weathertech mats, Mag-Hytec differential cover, Nfab bars, CB radio, Autonet wi-fi router, EGR bug deflector