[bocoogto]

When you accelerate when traveling 65-70, very little pedal pressure will result in a downshift and rpm's going from roughly 2000 to 3-4000 rpm. The 6-speed transmission has downshifted to allow quick acceleration if passing, etc. This is a normal condition with this easy-revving V6. With older 3 or 4 speed automatic transmissions, downshifting at this speed gives a much more abrupt jerk, but requires more pedal pressure by design. Or with a V8 that produces more torque at lower rpm's, this downshifting would not occur unless a lot of pedal pressure was applied.

I notice this whenever I switch from driving my '93 V8 Buick Roadmaster to the Enclave. The easy downshifting is a good compromise to allow rapid acceleration with a smaller engine. I'd guess the Lexus with an 8-speed automatic downshifts as easily, but smoother due to the availability of more gear ratios.

I don't believe there is anything wrong with your Enclave. In fact, I'd bet you moved from a V8-powered vehicle to the Enclave and experience the same thing that took me awhile to get accustomed to.