Rebellion Racing took a third consecutive World Endurance Championship pole position following an engine change between final free practice and qualifying in Austin.
Gustavo Menezes and Norman Nato sealed the top spot ahead of the best of the Toyotas after the team swapped the engine in the back of its solo Rebellion R-13 as a result of a sudden failure halfway through the second practice period.
Menezes went quickest on the first runs with a 1m47.674s and then Nato set a 1m48.087s before a brief red-flag period.
Nato improved to a 1m47.387s after the interruption to give the Rebellion a 1m47.530s average.
Jose Maria Lopez and Mike Conway took second in the more heavily penalised of the two Toyota TS050 HYBRIDs.
Lopez was third fastest after his run with a 1m48.634s, which Conway followed with a 1m49.688s to yield a 1m49.161s average.
Kazuki Nakajima had been eight tenths quicker than Lopez in the first runs with a 1m47.891s, but Brendon Hartley lost his first lap to a track limits violation.
He managed a 1m50.971s on his final lap before the chequered flag, which gave the #8 Toyota a 1m49.431s average.
Nicolas Lapierre and Antonin Borga took the LMP2 pole aboard the Cool Racing ORECA-Gibson 07.
Lapierre was second fastest after the first runs with a 1m49.343s, while Borga managed a 1m50.478s.
That yielded a 1m49.910s average, which was a tenth up on the 1m50.073s from Filipe Albuquerque and Phil Hanson in the United Autosports ORECA.
Nyck de Vries set the fastest P2 time aboard the Racing Team Nederland ORECA with a 1m48.696s, which briefly split the Toyotas during the first runs.
GTE Pro points leaders Marco Sorensen and Nicki Thiim took the class pole in the #95 Aston Martin Vantage GTE.
Sorensen led the way after the first runs on a 2m00.742s before his team-mate maintained the top spot on his first run.
Thiim then improved on his lap, getting down to a 2m00.725s to give them a 2m00.733s average and a two-tenth margin over the second-placed Porsche 911 RSR of Michael Christensen and Kevin Estre.
Christensen was only fifth in class after his run on a 2m01.106s, but Estre's 2m00.798s brought their average down to 2m00.952s.
Alex Lynn and Maxime Martin took third in the second of the Astons with a 2m01.029s average.
Gianmaria Bruni, who had been second after his lap, and Richard Lietz ended up just two hundredths back in fourth with 2m01.049s.
The two AF Corse Ferrari 488 GTEs took fourth and sixth after both lost times for track limits violations.
James Calado and Alessandro Pier Guidi just edged out the Porsche of Gianmaria Bruni and Richard Lietz for fourth, while Davide Rigon and Miguel Molina ended up sixth.
GTE Am pole went to the Project 1 Porsche 911 RSR qualified by Matteo Cairoli and Egidio Perfetti from the Aston Martin of Paul Dalla Lana and Ross Gunn.
|1||LMP1||B.Senna, G.Menezes, N.Nato||Rebellion Racing||Rebellion/Gibson||1m47.530s|
|2||LMP1||M.Conway, K.Kobayashi, J.M.Lopez||Toyota Gazoo Racing||Toyota||1.631s|
|3||LMP1||S.Buemi, K.Nakajima, B.Hartley||Toyota Gazoo Racing||Toyota||1.901s|
|4||LMP2||N.Lapierre, A.Borga, A.Coigny||COOL Racing||ORECA/Gibson||2.380s|
|5||LMP2||P.Hanson, F.Albuquerque, P.Di Resta||United Autosports||ORECA/Gibson||2.543s|
|6||LMP2||T.Laurent, A.Negrao, P.Ragues||Signatech Alpine Elf||Alpine/Gibson||3.454s|
|7||LMP2||H-Pin Tung, G.Aubry, W.Stevens||Jackie Chan DC Racing||ORECA/Gibson||3.824s|
|8||LMP2||R.Gonzalez, A.F.da Costa, A.Davidson||JOTA||ORECA/Gibson||4.062s|
|9||LMP2||M.Patterson, K.Yamashita, A.Fjordbach||High Class Racing||ORECA/Gibson||4.217s|
|10||LMP2||H.Hedman, B.Hanley, C.Braun||DragonSpeed||ORECA/Gibson||5.235s|
|11||LMP2||F.van Eerd, G.van der Garde, N.de Vries||Racing Team Nederland||ORECA/Gibson||5.601s|
|12||LMP2||R.Lacorte, A.Belicchi, G.Sernagiotto||Cetilar Racing||Dallara/Gibson||6.775s|
|13||GTE Pro||M.Sorensen, N.Thiim||Aston Martin Racing||Aston Martin||13.203s|
|14||GTE Pro||M.Christensen, K.Estre||Porsche GT Team||Porsche||13.422s|
|15||GTE Pro||A.Lynn, M.Martin||Aston Martin Racing||Aston Martin||13.499s|
|16||GTE Pro||J.Calado, A.P.Guidi||AF Corse||Ferrari||13.501s|
|17||GTE Pro||G.Bruni, R.Lietz||Porsche GT Team||Porsche||13.519s|
|18||GTE Pro||D.Rigon, M.Molina||AF Corse||Ferrari||13.699s|
|19||GTE Am||E.Perfetti, L.Horr, M.Cairoli||Team Project 1||Porsche||15.254s|
|20||GTE Am||P.D.Lana, D.Turner, R.Gunn||Aston Martin Racing||Aston Martin||15.300s|
|21||GTE Am||S.Yoluc, C.Eastwood, J.Adam||TF Sport||Aston Martin||15.379s|
|22||GTE Pro||J.Magnussen, M.Rockenfeller||Corvette Racing||Chevrolet||15.437s|
|23||GTE Am||C.Ried, R.Pera, M.Campbell||Dempsey-Proton Racing||Porsche||15.580s|
|24||GTE Am||F.Perrodo, E.Collard, N.Nielsen||AF Corse||Ferrari||15.846s|
|25||GTE Am||B.Keating, F.Fraga, J.Bleekemolen||Team Project 1||Porsche||15.920s|
|26||GTE Am||T.Flohr, F.Castellacci, G.Fisichella||AF Corse||Ferrari||15.932s|
|27||GTE Am||B.Curtis, A.De Leener, T.Preining||Dempsey-Proton Racing||Porsche||16.152s|
|28||GTE Am||M.Ishikawa, O.Beretta, K.Cozzolino||MR Racing||Ferrari||16.251s|
|29||GTE Am||B.Grimes, J.Mowlem, C.Hollings||Red River Sport||Ferrari||16.434s|
|30||GTE Am||M.Wainwright, A.Watson, B.Barker||Gulf Racing||Porsche||16.766s|