Driveshaft problems of the 2008 Toyota RAV4

Rear differential is making a loud rumbling noise in the beginning of 1st, and 2nd gear. Brought it in to Toyota and they said it was not leaking and I went into the shop and also looked at it myself and it wasn't leaking. Did the rear dif service like Toyota recommended because the car has been super reliable and I would like to keep it that way. I have done 2 rear dif services before and had no problems. Right when they did the service a couple days later it started making the rumbling noise again and is now leaking and made a puddle in my driveway. I took a look at it myself and all plugs are tightened but it is now leaking from the coupling where the driveshaft connects and the drivers side axle seal. They want me to pay 1000 dollars for a whole new coupling assembley that is refurbished not including the ds axle seal and labour. I will post picture below of the problem.

The contact owns a 2008 Toyota Rav4. While driving 45 mph, the vehicle vibrated without warning. The vehicle was taken to the local dealer (vic's auto service located at 3400 south park Ave, buffalo, NY 14219; (716) 822-3404) where it was diagnosed that the entire drive shaft needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 49,000.

2008 (started at 20,000 miles, 1 year out of warranty) Toyota rav 4 started a clunking noise in the drive shaft when turning the wheel. We took it in for service and the dealer said they could not duplicate the problem. It's a constant sound! why they said this is unexplainable. It's been non stop since and getting worse. We read on the internet this is common problem for rav 4 owners. We will be taking it back in again and will probably be told the same thing. I also understand there is a tag issued for this problem by Toyota also. The repair is averaged to be $800 and some dealers are willing to share in the repair cost. This should be Toyota's 100% responsibility!.