I recently picked up my grandfather's 1991 F350 a couple weeks ago.
The last couple short drives it's been feeling like I'm pulling his old fifth wheel trailer, with nothing behind me. Maybe it's me, I have been driving my wife's Vue around, and I haven't had the truck back for very long.

I thought the brakes might be dragging, but the wheels and drums are cold.

Any ideas?

1991 F350 Dually, 7.3 IDI (NA), manual transmission - if it helps.

Pops said the clutch was going and the rear brakes like to lock when I got the truck, but hasn't seemed to be an issue yet. It doesn't feel as if it is either.

 

That's a big truck, and IDIs are great engines but they don't make a ton of power. My guess would be that you're just not used to it from driving the car.

If you go a while and you still feel like something's weird, then check on all the brakes like you're saying.

What kind of gearing do you have? With big gearing (4.11,4.56) you may not have that much less stress on the engine without the fifth wheel. My 460,C6, 4.56 feels about the same driving empty as towing 6.5k. The gearing just isn't stressed that much.

 

Where does the rattling sound like it's coming from? I've seen a bunch of IDI motors with manuals behind them that the flywheel chatters when you start it and shut it off.

 

The e brake cables like to rust a freeze keeping a slight drag on the rear brakes which seems to go away after you drive it a while. Get them checked out and replaced.
It took two different shops to find mine.
Good Luck

 

After driving it around a little today it seemed to go away, I think you may be right about the parking brake cables. I left it in gear last night when I parked it, and left the brake off. I will be checking it when it warms up a little. It is also 25 degrees warmer today than it was last night, if it makes a difference.

It does run 4:11, according to my father.

Although I didn't mention it, it does chatter/shake on cold startup and turning off.
I've always thought it was normal for a truck of this size and fuel type.
Not my first diesel, and not my first large truck, but it is my first combining the two.

This truck has now been a part of three generations in our family (big car family), I hope to keep this one for the next of kin.

I'm normally a classic VeeDub and old school Chevy guy, but have always held a spot in my heart for a dang good Ford diesel. So most of this is still new to me.

I'm new to this site, and I do appreciate you guys' help.
Thank you!