My friend has a 5.7 Suburban that he will sell to me for 800. He has had it since 2005, it's lifted on I believe 315's, has 225,000 miles, and has a bad transmission or something. He puts it in gear and floors it but it goes nowhere and he assumes the transmission just went and needs to be replaced. I'm not sure if it would be worth buying and putting a used transmission in so I was looking for advice on what I should check and replace before buying a transmission if it is even worth buying. It only has some surface rust and the brakes were redone when it was lifted. I have spent hours reading about these vehicles but havent learned as much as I'd like to. Any help and advice is greatly appreciated as I don't know much about Suburbans.