I have a 4x4 1968 f100 4 speed and when i reach anywhere between 55-65 mph theres an intermittent resistance? I'll hold my foot steady and then it feels as if it slows down for a second then goes back to normal. Any ideas as to what this could be? My next problem is a scraping sound at 25-35 mph, sounds like its coming from the passenger wheel but ive taken it apart and have no clue what it could be.

Thank you

 

The first thing that comes to mine is perhaps a drop in fuel pressure. What motor do you have? What type of fuel system does it have?

That sounds like a u-joint. If it were a dust shield, it should make noise all the time. Throw out bearings are also prone to making noise at different speeds.

 

Its a 360 FE with a new fuel pump and edelbrock 4 barrel, are you talking about the axle u joints? Or driveline?

Thank you

 

Driveline u-joints. But, since you mention it, the front ones shouldn't be turning unless you have the 4x4 engaged, or the front hubs are locked. If they are turning, then perhaps the squeak is coming from them? Also, if it's in the clutch, you should be able to duplicate that sitting in neutral with the clutch out.

 

I assume your truck does not have AC. I see similar complaints with a low Freon charge.
Drum brakes all around? Check for shoes scrubbing the drum and improper bearing preload. Or just a bad wheel bearing.