Re: 1999 explorer sport shifting to 4th too soon
There should be an overdrive lockout button on the dash or on the end of the shifter. That will lock out overdrive and keep the vehicle in the gear that is 1:1, generally 3rd in a 4 speed transmission. Normally a shift into OD won't come until around 35mph, and even then, depending on tire size and axle gearing you'll be lucky to do around 1200-1400rpm at that speed. Ford automatics are generally geared toward fuel economy, but that seems a bit extreme to go into OD at 25mph. I'd guess there might be a problem with the torque converter. I'm not a trans man by any means, but perhaps someone else will chime in.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!