All mid 2008 through 2014 Polaris RZR 800 series have a big problem with the rear differential pinion nut backing off, allowing the pinion gear to shoot into the rear differential, destroying the rear differential. This has happened with machines with as little as less than 100 miles on them! Reports indicate that there are no problems, nor warnings, until the rear differential grenades, locking the rear axles solid! This requires the machine to be lifted onto a trailer, to be transported for rear differential replacement, as it destroys the case. After failure, rear differential replacement can be quite expensive: labor alone can run from $800-$1200 and a new OEM Spicer rear diff, if you can find one, can run from $1700-$2500! So, if you own any Polaris RZR 800 series between the years of 2008-2014, I recommend that you do this repair before further use of your machine. personally, I have grounded my machine until it can be done. Please check the online post for your own awareness.