You can download 3 hr rainfall data from CMORPH http://www.cpc.ncep.noaa.gov/products/janowiak/cmorph or 3B42RT with 0.25X0.25 deg resolution and upscale it to 0.75X0.75.
Reanalysis based (NCAR), but corrected to observations is the princeton forcing: http://hydrology.princeton.edu/data.pgf.php, available as 3hr values e.g. for 0.25° (use CDO for time and resolution changes)
Same (but for ERA-Interim) is the WATCH Forcing data http://www.eu-watch.org/data_availability but I think only for 0.5 deg
You may use GLDAS precipitation data. The data is available since 1979, in two spatial (25km and 100km) and temporal (3hr and monthly) resolutions. Here is the link:
I recommend to use CHIRPS from the USGS which has a 0.05 resolution and spans the globe between 50S - 50N. The monthly series have more than 30 years (1981- up to date) and combine satellite data + gauge stations around the world. You can choose the format more convenient to you:
CPC (Climate Prediction Center) rainfall data are available from 1979, also in near real time, with a spatial resolution of 0.5° and daily temporal resolution: