I have started it and checked the gauges in reverse it show and R and that its in AWD but the front wheels wont move

 

Try putting it up on axle stands (but under the a-arms so that you dont cause the CV's to bind at full drop) and try again.....the fronts don't actually engage unless the rear lose traction.....just to eliminate that before you tear into your front diff

 

It was in the mud rears where spinning and fronts would not. The guy i bought it off of said he put a newer low miled front Diff. for what reason i do not know. I thinks its an electrical problem but im not for sure

 

Download a 2008 service manual from the forum There is a section dedicated to trouble shooting AWD in the manual. Teamhog a member of the forum has the manual available for download.

Polaris RZR Forum - RZR Forums.net - View Profile: teamhog

Look toward the bottom and you will see dates for manuals.

 

Turn key on put in drive and turn on 4x4 switch, is the car like symbol showing in the gauge in high and low, indicating 4x4 ? From what you described it should be showing the car like symbol, because you have four wheel drive in forward, now shift in to reverse, if you lose the car like symbol in the gauge, it is electrical. This was my problem. Try leaving it in reverse with 4x4 on and I want you to move a wire around while looking at the gauge. this wire is cross from the starter. As I moved it I saw the 4x4 come on and go out. So I changed that peace of wire harness. It's a little tricky, there are spring loaded pins.
Good luck, keep me posted.

 

The switch puts power to front end. The front end gets it ground thru the instrument cluster. It must see a movable gear and under a certain amount of rpms to give the front end the ground. Id run a 12 v positive and ground straight to front diff and try it

 

First off do you have 4wd in forward? If you do then it's likely not an electrical issue unless the R or AWD logo doesn't light up on the dash when enabled in reverse. I had the same problem with my 2008 Rzr the plastic cage in the front diff had cracked and only sometimes 4wd worked forwards but never in reverse. The late 2010 and newer diffs all had aluminum cages from the factory, I upgraded to the stronger xp front diff and its been great since.

 

I have an 09 rzr 800 with the plastic cage and nothing seems broken inside the front chunk. It doesn't come out of awd in forward even by flipping the switch and it doesn't go into awd in reverse at all. Any suggestions?