I assume you are asking about the United States’ Constitutional Convention that met in 1787 and wrote the Constitution that we now have. There were three major disagreements over slavery that arose in that convention.
The first dispute concerned whether the right to slavery should be enshrined in the Constitution. The Southern delegates wanted the Constitution to explicitly recognize and protect the right to own slaves while the Northern delegates did not. This dispute was settled in favor of the North. There is nothing in the Constitution that explicitly provides the right to have slavery.
The second dispute had to do with the slave trade. Southern delegates wanted to protect the Atlantic slave trade. They did not want the government to be able to ban the importation of slaves from Africa. This, too, was settled in a way that favored the North. The government was prevented from banning slavery, but not for very long. The North only agreed to protect the slave trade for 20 years, not indefinitely as the South would have liked.
The final dispute had to do with counting slaves for the purpose of Congressional representation. The South wanted slaves to be counted in their states’ populations. This would have helped the South because it would have given Southern states larger populations and, therefore, more representation in the House of Representatives. The North did not want slaves counted at all. The compromise here said that slaves would be counted as 3/5 of a person for the purposes of representation.