Transmission Noises

I drove Little Kat to college. I took his car because it has a college parking pass. Each time I pressed the gas from a stop, I heard a strange sound and felt some sort of rumbling in the vehicle. I asked Little Kat about it. He said he did not notice anything. I did a second test drive and felt the problem again.

Little Kat and I dropped the car off at my mechanic's. We pulled into the garage. Waited 20 minutes for him to show up. Ended up leaving it with some other employee. I called my mechanic. He said he did not feel or hear what I described. He said the transmission was a little jerky. But he could find no problem.

I don't want to have to pay for a new transmission or engine. That could run from $5k to $10k. The car is 5 years old with 27k miles. Online I got an estimated trade in sale price of $10k to $11k. I priced new cars with the same trim. MSRP is $21k+. But with $2500 of discounts, the car would cost $19k+. So maybe $11k total out of pocket to trade up to a brand new car.