The gerrymander is reflected on the fact that the Democrats had a 22-2 delegation in the 95th congress and how the districts voted for president in 1976 (Carter won the state 51-48)
The 93rd Congress was the first after redistricting. Republicans picked up TX-5 Alan Steelman, and Bob Price held TX-13 (he had been elected from TX-18 in the Panhandle. TX-13 and TX-18 were merged, which is where the Amarillo-Wichita Falls linkage started.
Price lost in Watergate 1974, and Steelman was beatern in 1976. But by the end of the decade Republicans had picked up 3 seats that had to be converted into Republican sinks (TX-22 when Ron Paul replaced the retiring Bob Casey, TX-21 where Tom Loeffler replaced Bob Krueger who lost in a run for the Senate, and TX-8 where Jack Fields defeated Eckhardt.
And in 1983 Gramm was elected as a Republican in TX-6.
so overall, the number of Republicans increased from 3 to 6 over the decade.
well the lines were actually redrawn for the 1974 elections. The changes were pretty minimal except for in the DFW area. The 5th district lost the park cities which made it more dem leaning. The 24th district also lost Denton County. The 3rd district not only gained the park cities but also gained parts of Collin County and SE Denton County, where there was a lot of new subdivisions and presumably a place where republicans were moving into. So the 3rd was a mega-pack.
They wanted to keep those areas out of Ray Roberts district to prevent him losing down the road. Had Plano been kept in CD 4, it likely would have gone republican in 1980, when Roberts retired and Hall won by only a 52-48 margin. Also, Gramm didn't switch parties until after the 1980 census map came out. Another thing is that Steelman didn't lose re-election. He was the closest thing in Texas to a moderate republican and he gave his seat up in 1976 to run against Bentsen.