On the way back from a four-wheel-drive exploration of Utah's wilderness — from and to New York — the differential blew in Davenport Iowa (3 AM Sunday morning in the rain). It was towed to Smart Toyota. They said that the entire differential had to be replaced, and had to wait four days for the parts. I was charged $3100 (over the 2500 original estimate because brake lines had to be replaced and the parts were rusted so badly). Finally got out of there the following Saturday — and I started hearing a noise in Ohio. I looked underneath and there was fluid all over the differential and spare tire. Virtually nothing in the differential itself. I put in 3 quarts of 5W-30 and stopped at the next pilot truck stop and grabbed all their gear oil. I then drove for an hour — at 50 miles an hour — and then added a quart or more. 8 quarts later my wife and I got home. Discovered a leak in the differential about 6 inches above the filler hole. When it was just parked it didn't leak. When I jacked up the rear end — tires off the floor — and ran it through the gears it leaked. I fixed the leak with epoxy. I can hear the noise in the garage when I run into the gears with the tires off the floor: a whine or howl at certain torques. I tried 85W- 140 gear oil but it didn't help. I told Smart Toyota service managers the whole story. I have an appointment with Dorschel Toyota in Rochester New York (50 miles north of me) June 1 at 10 AM. I didn't tell them about the leak — yet — because I'm afraid they'll say that that voids the new part warranty. But they started saying things like it might be the carrier bearing or the wheel bearing, and I know it's not. I'm afraid they'll do work it doesn't need and still not fix the problem. (I normally do on my own repair work because every repair I've ever has been screwed up, but differentials are beyond me..) the new differential only has a one year warranty and here at home I only drive about 1500 miles a year (when not going on long trips). I'm afraid they might say also to just wait and see if it gets worse. But it has been getting worse since I first heard it in Ohio. I'm afraid they might stonewall until the year is up. Any advice? Should I tell the dealership about the leak? I'm afraid they'll say that is Smart Toyota's problem, and not cover the repair. The frame was replaced a year and a half ago and mechanically otherwise it's still in good shape. It has a homemade camper top which is the devil to transfer to another vehicle. I wanted to keep this until self driving trucks arrive. 135,000 miles.