Into the ninth hour and with the field under caution the first gaggle of Prototype runners to pit featured the top four cars, both ESM Nissans, the #5 Action Express Cadillac and the Penske ORECA.
As the race went green it was Joao Barbosa on the move, dragging by both Nissans, which had reversed order in the pits, Pipo Derani getting the #22 out first ahead of Dalziel.
Dalziel was immediately under pressure from Montoya, now back aboard the #6 and looking to keep in touch with the lead battle.
That was interrupted by a huge accident for Robert Alon which comprehensively demolished the front of the #14 Lexus, into the tyres hard at the exit of the final turn without contact from another car, there was a brief fire, Robert decamping under his own steam but clearly very shaken.
Back to green with 95 minutes remaining and Barbosa was immediately under pressure from Derani, the Brazilian through to retake the lead on the first Green flag lap.
Jack Hawksworth meanwhile was in trouble, a 2 minute stop and hold for improper pass around going the way of the #15 Lexus, then running third in GTD , not a good few minutes for 3GR.
In GTLM Alexander Sims was holding Ryan Briscoe, Antonio Garcia and Alessandro Pier Guidi at bay.
Derani was getting away at the front with Montoya looking increasingly raced as he got onto terms with Barbosa, out of Turn 10 Montoya looked up the inside , a touch, the ORECA got a wiggle on, dropped back and was immediately under pressure from Dalziel and Conway directly behind. 80 minutes remaining.
But the contact had a bigger drama to offer, the #6 into the pits, a broken rim and the team opting to change all four, the image actually caused it seems not by the rub with Barbosa, but rather by a chop on the #15 Lexus that left both cars damaged, the RC-F rather more sop, the team scrambling to avoid a double DNF.
72 minutes remaining and in came the #2, left side tyres changed and Brendon Hartley reinstalled.
Barbosa followed suit next time around, Albuquerque aboard #5 for the finish.
Derani was next, all four tyres changed for the #22, Mike Conway to the lead in the #31 to pit next time around himself, Dane cameron into the car with all four tyres changed.
The already heavily delayed #24 BMW looked set to retire just before the final hour, pitting with clouds of smoke and steam and a pool of fluid under the car.
Into the final hour and Dane Cameron was the man on the move – up to 4th ahead of van der Zande in the #90 Visit Florida Ligier.
The #86 Acura was posted as an official retirement.
The top 5 with an hour to go:
Albuquerque #5 +8.7 secs
Hartley #2 +10.6
Cameron #31 +19.7
van der Zande #90 +20.2
Briscoe #67 +3.5
Garcia #3 +5.7
Pier Guidi #62 +7.8
Vanthoor +#912 +10.8
52 Minutes and Montoya was up into 5th ahead of van der Zande, the #90 still hobbled by a misfire.
The GTLM stops came at around 51 minutes to go, the #3 pipping the ##67 to exit the pits ahead, the Risi Ferrari went around for another lap before pitting for its final full service, Vilander climbing aboard and emerging fourth, under 10 seconds from Sims in the leading BMW.
The Land Audi (de Philippio at the wheel) meanwhile holds a heathy advantage over the chasing #28 Alegra (Christensen) and #73 Park Place (Bergmeister) Porsches (33 and 48 seconds back respectively with the #33 AMG running fourth a further 4 seconds back with Jeroen Bleekemolen at the wheel.
43 minutes and Sims was struggling in traffic, and being caught but Garcia and Briscoe with Vilander closing in fast too.
42 minutes and Montoya was the first of the leading group to make a final stop, fuel and four tyres.
Hartley caught Albuquerque and executed a clean pass from Turn 7 just before the 14th FCY was shown, the Performance Tech ORECA PC car into the gravel T1 after contact with the #23 Audi.
The ORECA was recovered to the track but then could not turn sufficiently to continue, the FCY would be a little longer!
33 minutes, both ESM and both Action Express cars pit under the Safety Car. The #22 emerges first, the #5 crew getting Albuquerque out ahead of Hartley again. There will be under half an hour remaining when the race goes green again.