I bought a mint 1990 Pathfinder to tow my boat. The boat is a 17' bay boat with a 90 hp engine, not a small boat, but not nearly a big boat. I estimate boat and trailer at about 1900#. The Pathfinder tows it very well, except for one problem. I'd like to be able to tow it at 70 mph, just to keep up with most trafic on the interstate (which is mostly going 75-80), but when I get a little over 65mph it keeps shifting out of overdrive back down into 3rd gear, and goes from about 2600 rpm to about 4000 rpm. Obviously, I don't want to run it at 4000 rpm for several reasons, so I don't want to just turn off the overdrive. I see two options, and would like some input from anyone knowledagable people. First, I could put a lower gear ratio into the rear differential (it's 4wd), which would bring up the rpms a bit, to say, around 3000 and hopefully that would enable it to quit jumping in and out of OD, (I don't really do much 4 wheel driving, and when I do, it is no very loose soil, or sand, so there should not be a problem with the front and rear differentials being slightly different) or secondly, I could add some components to boost the HP a bit (I think that that year has only 145) so that it would not have to hop in and out of OD. Clearly, I'd like to be able to boost the HP by about 15 or so, which I think might solve the problem. What would anyone's recommendations be? Thanks.