Replacing Gear Oil -- Synthetic Questions??

Currently drive a 2002 Trooper w/ 60K miles.

I need to replace my front axle, rear axle and transfer case fluids....Been thinking about switching to a synthetic.

I have two questions for you guys....

1. What brand/type/weight of synthetic do you recommend?
2. Will a synthetic oil cause any problems with the seal, gaskets, etc.? (just don't want to start leaking or something like that).

Hi, I have a 94 trooper that I bought at 120,000 miles. It now has over 135,000. After I bought it, I switched to Mobil 1 synthetic engine oil, and had no problems or leaks. I also changed the transmission filter and fluid to amsoil synthetic and have no leaks there either. I changed the transfer case oil as recommended with basic engine oil 30W, but changed out the front and rear differential cases with mobil 1 synthetic light truck diff. fluid, which I think was 90/120 or thereabouts. All is well with them as well.
I will say that if you do have any seepage or leakage now, the synthetics will more than likely do the same. The synthetics do seem to flow better than traditional oils, so if there is a place to leak, it will find it. Sometimes, the new oil with its new additives will improve things due to the refreshed additives that help clean and preserve seals etc;.
Just my opinion, but I like the synthetics!