Need Advice Transmission

My girlfriend has a 2006 tacoma prerunner 4 door. It has 93000 miles. Now typing this it hasnt done it the past two times we drove it but it is still a worry. When you crank the truck up and put it into gear its all normal but when you hit the gas it holds like the parking break is on and then just slams like hell. This only happens on the initial startup. Does not ever do it again under any circumstance. Other than that the truck is perfect. Has never had any other issues. However, she took it to the toyota dealer where she bought it cause her warranty just went out so they said bring it up and well see what we can do. They found her axle seal leaking which to me makes no sense. I have a 2004 tacoma and my axle bearing went out and it was not even close to the symptoms of her truck. They said that she needs a bearing a seal and all that but to me makes no sense. Im a garage mechanic that can do a few things but just need a pointer on what im looking at. Im thinking it is an electrical transmission issue. Any info would be greatly appreciated. Thanks!

 

Have you checked trans fluid level? If you don't know how there is a link on how to check it on here. There is no dipstick like most transmissions would have. That would be my first check.

 

I have not checked the fluid. I will do that when I get home today.