All the goals came in the first half, with Dennis Oli opening the scoring in the 19th minute.
Midfielder Tom Youngs equalised for the home side three minutes later, only for French forward Sabin to restore Rangers' advantage with six minutes of the first period remaining.
Northampton threw the kitchen sink at the visitors in the second half but couldn't find a way through and Rangers held on to secure a good win.
Jamie Cureton and trialists Paul Warhurst, Simon Jackson and Karl Beckford all enjoyed a full 90 minutes against the Cobblers.
Manager Tim Breacker was pleased with the result and the performance.
He said: "We were holding on in the second half a bit, but I was pleased with how we played overall - particularly the young ones.
"We got to grips with their system, which was a little different than what we were used to and by the end of the first half we were on top.
"In the second half we had to deal with a lot of pressure and in the end it was a typical away performance. We scored the goals that mattered and kept Northampton out."
Breacker was also pleased to see Jamie Cureton come through the game unscathed and believes he is heading in the right direction.
He said: "He hasn't played a full game for three months and he really needed the game. He has to get some football under his belt and we are all working towards getting him back to his best."
As for the trialists, Breacker remains open-minded. He said: "The two lads from Charlton were always going to find it hard to come from the Academy Premier League, to Second Division reserves - the emphasis is on different things at this level.
"But they acquitted themselves well and showed that they could adjust.
"Paul Warhurst hasn't played for a few weeks, but he did what was asked of him and Ollie and Kenny will both speak to him to see where we go from here."
Rangers: Day, Jackson, Brazier, Coke, Warhurst, Fletcher, Oli (Townsend), Beckford (Mills), Farr, Sabin, Cureton