2007 Chevy Silverado Leaked fluid?

[Jasmin]

I pulled up to my house and put my truck in reverse and pressed the gas it made a loud slam like the gears were jammed into place,and it sounded like the gears were slipping. I immediately put it in nuetral and waited a sec and then put it in reverse and it was fine. I backed into my spot and got out and noticed a line of fluid from where the gears did the jammy thing to where I parked. I looked under the truck and saw fluid leaking from the crossmember of the truck. But when I got under the truck I could not see any visible fluid coming from anywhere but a small hole in the crossmember. The fluid did not smell and it was clear. But I could not tell for sure because I could only touch what was on the ground. Also the fluid was cold and I had just got back from a 4 hour drive. My truck is 4 wheel drive and has the 5.3 engine. please help!