Will the transmission from a 1999 Yukon Denali fit in a 2000 Yukon slt?

Yes, the transmission from a 1999 Yukon Denali should fit in a 2000 Yukon SLT, as both vehicles share similar drivetrain components and are part of the same generation. However, it's essential to verify compatibility by checking the specific transmission model and any potential differences in electronic connections or mounting points. Always consult a professional mechanic or refer to the manufacturer's specifications for confirmation before proceeding with the swap.