How to Change the Transfer Case Fluid (Alternate Method)
This is for folks who still have the original OEM pipes, or OEM head pipes with an aftermarket slip on such as the Roadhouse.
The transfer case fill/drain/inspection holes are directly behind the exhaust pipe. Yamaha's instructions in the service manual have you remove the exhaust to do it. The below instructions show you a fairly painless way of doing it without removing the exhaust. Essentially you end up filling the bike back up with gear oil by using a hand pump to squirt it in through the level check hole rather than through the fill plug - which is impossible to get at without removing the exhaust. I did it with a cheap pump that I found in the auto section at Walmart and it worked great.
1. Ride! Take a miniumum 10-15 minute ride to fully warm up the oil in the transfer case so it will flow out easily once you pull the drain plug.
2. Put your bike on a lift, stand or prop it upright with a brick or block of wood under the stand to get the bike in a level position. A lift is your best bet since it'll give you more room to work with.
3. Behind the muffler just aft of the exup valve is the transfer drain hole. It is blocked by two control lines wrapped in heat insulation. The insulation is held in place by black tie wraps. Using pliers, squeeze the retaining clips and slide them out of the bracket that holds them in place.
4. Remove the transfer case inspection bolt using a 4mm allen wrench.
5. This next step requires a wrench that'll fit in the small space between the pipes and the transfer case. I used a 3/8" drive ultra thin head Craftsman ratchet part # VV-44995 along with Craftsman T40 Bit part # 42665. Using the wrench and the t-40 bit, remove the drain bolt that's behind the insulated lines. With the retaining clips loosened from the brackets, you should be able to push the lines out of the way to give you better access. Don't lose the washer when the drain bolt comes out!
6. Let the oil drain out into a drain pan.
7. Reinstall washer and drain bolt.
8. You will now refill the transfer case through the inspection hole using a hand pump. I used one that I bought for a few dollars at Walmart in the automotive section. I had to whittle away at one of the included tips to make it small enough to fit in the inspection hole. Others have had success using Amsoil pumps. For the oil, Yamaha specifies SAE 80 API GL-4 Gear Oil. Warming up the oil a little will help it flow more freely. Occasionally remove the pump to see how close you're getting to the fill level (fill level is the bottom rim of the inspection hole when the bike is LEVEL). If you overfill, just let it drain back out of the hole until it stops - that'll get you back down to the bottom rim of the hole. The 'liners should take a bit over half a quart.
9. Reinstall the inspection bolt.
10. Slide the black tie wraps' retaining clips back onto the bracket
11. Go for a ride!
And here's nice DIY tool/ fill-plug adapter from Artstoy>