Gmc Denali Questions

2002 denali xl..when driving 60 65 truck makscopeland61es and noise ...

2002 denali xl..when driving 60 65 truck makscopeland61es and noise like a18 wheeler down shifting gears and vibrates...purchased new tires about 6 months ago could it be the tires...help need some answers

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I replaced the fuel pump on 2000 Gmc Denali, now there is a strong smell of gas coming from the bottom of the vehicle. What could cause that ?