While the following is INSERTED INTO movie's last scene with Jack and Ennis together, Annie Proulx wrote it as being something that happened AFTER the two guys split up in 1983.
The first quote is from the trailhead parking lot and it took place with Ennis talking to Jack, who is already in his own truck ready to drive off. Ennis waited until the last minute to tell Jack that there was a change of plans.
. . . Ennis stood as if heart-shot, face grey and deep-lined, grimacing, eyes screwed shut, fists clenched, legs caving, hit the ground on his knees.
"Jesus," said Jack. "Ennis?" But before he was out of the truck, trying to guess if it was heart attack or the overflow of an incendiary rage, Ennis was back on his feet and somehow, as a coat hanger is straightened to open a locked car and then bent again to its original shape, they torqued things almost to where they had been, for what they'd said was no news. Nothing ended, nothing begun, nothing resolved.
In the text, there is triple line spacing between the above and the below to show a time lapse and/or a change of location.
I say that it is both.
What Jack remembered and craved in a way he could neither help nor understand was the time that distant summer on Brokeback when Ennis had come up behind him and pulled him close, the silent embrace satisfying some shared and sexless hunger.
They had stood that way for a long time in front of the fire, its burning tossing ruddy chunks of light, the shadow of their bodies a single column against the rock. The minutes ticked by from the round watch in Ennis's pocket, from the sticks in the fire settling into coals. Stars bit through the wavy heat layers above the fire. Ennis's breath came slow and quiet, he hummed, rocked a little in the sparklight and Jack leaned against the steady heartbeat, the vibrations of the humming ike faint electricity and, standing, he fell into sleep that was not sleep but something else drowsy and tranced until Ennis, dredging up a rusty but still useable phrase from the childhood time before his mother died, said, "Time to hit the hay, cowboy. I got a go. Come on, you're sleepin on your feet like a horse," and gave Jack a shake, a push, and went off in the darkness. Jack heard his spurs tremble as he mounted, the words "see you tomorrow," and the horse's shuddering snort, grind of hoof on stone.
Later, that dozy embrace solidified in his memory as the single moment of artless, charmed happiness in their separate and difficult lives. Nothing marred it, even the knowledge that Ennis would not then embrace him face to face because he did not want to see nor feel that it was Jack he held. And maybe, he thought, they'd never got much farther than that. Let be, let be.[/size]
IMO, "Let be, let be" is Jack's response to the "Nothing ended, nothing begun, nothing resolved" situation when he was last with Ennis. I just believe that Jack decided to "let Ennis be' and get on with his own life without Ennis.
Ennis's setting all the rules for his relationship with Jack made Jack miserable. Because of his fear of being found out that he was "queer," even at 39 years of age, it was always Ennis who decided when and where the two would meet. Ennis never wanted to do what Jack suggested after they first "fishing trip" in 1967.
Jack did not have to stop loving Ennis to let him be and take charge of his own life. Annie Proulx's Lureen took on her father's persona and after her father died, she took over the Farm and Equipment company and became Jack's boss (he had not worked for the outfit until Lureen was the boss).
Since this subject thread is in the open forum group, I prefer to believe that Jack just decided to stop trying to please both Ennis and Lureen and move on with his own life. Jack had been a failure trying to please his own father; but, at least his Mom knew that he tried. I just believe that since Jack knew, or at least guessed, that Ennis would never ask for proof of his "accident," he would find a way to get out of the way of his wife and his (sort of) husband.
I am saying that Jack did not have to fake a death to get Ennis to believe he was dead; he just had to have at least two people make Ennis think he was dead and that was Lureen and his father. The way that Ennis talked about "the tire iron" in the motel room in 1967, I wouldn't have been surprised if Ennis mentioned a truck tire iron quite a few times between 1967 and 1983 . . . especially when Jack brought up the subject of them living together.