Hi, I have a 1996 4x4 f-150 351 5.8 V8. E40d transmission.
truck starts fine, idles fine, sounds fine, but when going on to On ramps or areas I need to step on it, it down gears but doesn't pull hard, Rpms increase by a thousand and slowly make their way up and doesn't up shift until I let off the throttle a little bit, once I get to speed on the freeway no problems runs great until I need to step on it again, no pull, and when it does shift it's a little hard. No check engine light no codes, good compression/spark it doesn't misfire at all, I checked ATF fluid, looks good doesn't smell burnt or anything, it's just almost like the gears are slipping when I need the torque, if I'm driving slow it shifts by itself and everything's fine, but when I step on it or climb a hill theirs no power, doesn't shift until I let off the throttle. No whirling sounds clunks or shakes. My guess's are either the torque converter, or the shift modulator, any advice or help would be much appreciated!!

 

What's a shift modulator? I've never heard of that.

I think your problem is the engine is down on power. Get that fixed and you'll find the transmission, torque converter, and shift modulator are fine.