The result means Ally McCoist’s men move six points clear of the Steelmen as both teams challenge for second place in the SPL with just six games remaining.
It was the home side that opened the scoring in this hard-fought battle with Estonian forward Henrik Ojamaa rolling the ball into the net after just six minutes.
But Rangers immediately bounced back with Steven Whittaker firing home a terrific long-range effort for his first goal of the season.
Once again refereeing decisions will be questioned and none more so than Ian Brines’ call to book Sone Aluko for diving rather than award a stonewall penalty before the half hour mark.
But in the end this didn’t prove crucial as McCulloch’s goal secured three massive points for the Light Blues at the end of a pulsating clash at Fir Park.
The match started at a furious pace and Motherwell stunned their guests with a well-worked goal.
Chris Humphrey used his pace to burst down the right wing and after making his way into the 18 yard box the accuracy of his cutback to Ojamaa meant the Estonian had the easiest of tasks to find the net.
Rangers, however, responded in style and just two minutes later Whittaker smashed home a wonder strike.
The Scotland right-back picked the ball up 25 yards from goal and unleashed a powerful, left foot drive which flew past Darren Randolph before the keeper could move.
It was a moment of quality from Edinburgh born Whitts who, on 13 minutes, clashed with Tim Clancy and both players were booked albeit it seemed harsh on the Gers star who appeared to receive a head butt to his chest.
In the early stages Ojamaa’s movement and link up play was impressive and on 22 minutes the striker teed up midfielder Nicky Law but despite making a lung bursting run his shot lacked the power and accuracy to beat McGregor.
But prior to the half hour mark came the moment of controversy.
Aluko sprinted clear of the Well defence and there looked to be contact when the Nigerian attempted to skip around Randolph who had darted off his goal line.
Brines assessed the situation and after looking towards his linesman decided to book Aluko to the amazement of the winger who showed the ref where the contact had been made.
The Gers number 19 waited to speak to the officials as they walked up the tunnel at half time but with the match level at this stage fans were looking forward to another 45 minutes of drama and action.
As expected the high tempo continued and, with both managers sticking with the same players for the restart, further chances were created.
Keith Lasley stung the hands of McGregor with a powerful long-range effort before Papac’s deep cross was met by Whittaker who was stretching and could only head over the bar.
On 62 minutes McCoist made his first tactical switch with Kyle Lafferty replacing Papac, which meant Steven Whittaker moved to left midfield as Gers moved to a 4-4-2 formation.
With the clock ticking down the visitors kept the pressure on and Davis was unlucky with a back post volley after Aluko had picked out the Ulsterman with an intelligent delivery.
The Ibrox skipper then stepped up to take a free-kick from 25 yards but the ball flew high and wide to Randolph’s relief.
The Motherwell goalie was certainly the busier of the two shotstoppers but with just ten minutes left McGregor had to be at his world-class best to deny Michael Higdon.
This proved so crucial as Gers went up the park in search of a winning goal and it would eventually arrive.
Aluko had his head in his hands when he missed a snip from close range but when the ball came back in from a throw-in McCulloch reacted quickest in the six yard box to fire the ball into the net in front of the ecstatic travelling Bears.
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