Question about shift points on D1

[Viggen]

So, a friend of mine is selling his D1 auto. I drove it for a week and it was great. My question though is about its shifting habits. It will get a trans flush and new filter but it really didnt want to stay in O/D which killed any semblance of gas mileage. Is the O/D linked to revs or speed? Its lifted (about 4"), has a 3.9, stock gears (believed to be) with locker in the rear and, if I remember correctly, 255/ 85's on her. Im thinking about buying her but the fact that its going to have to be driven on the highway to get to any good woods and having it turn 3k+ at 55-60 mph is too much I think. Is there a way to adjust the kick down? When I was driving it, it would kick into O/D at around 60 and then the moment it dropped in speed, the downshifted and the revs jumped up. Is this normal?

 

[RonL]

What you are feeling at 56-58 mph(when driving normally) is the torque-converter locking up, not OD.

I want to understand what you are saying correctly,

1. when it downshifts out of OD, it is then at 3000rpms at 60mph?

2. You feel that 3000rpm is too much?

3. Are you driving in the "hills" of VA?

From what I know, a 4" lifted rover with 255 tires, you will be driving in 3 gear anytime you head up hill. In CO, I was in 2 gear at 4000rpm going up hill.....

 

[sven]

Stock gears is gonna be the limiting factor here.

 

[Viggen]

Va is pretty hilly and if it locked up and then shifted into 4th or 3rd going up slopes but it seemed to never lock up. I guess its gearing thats keeping it from shifting at the perceived correct points?