Rear end question (the one in the truck, okay?)

[Yardpilot]

I do ask lots of basic questions. Like lots of folks, I have picked up bits and pieces over the years rather than any comprehensive knowledge set. Some things I have down in great detail, while others are sketchy at best.

I'm kinda wondering about the rear end in this ol' girl. 1973 F100. This truck was a 240 6 with a three speed. Now it is a 351 C 4v with a C6. Two grand on the tach is 54 MPH indicated, 56 by the clock. Is there likely to be durability issues with this rear end? I have a 78 F250 4x4 parts truck. Would that rear end work if I needed it?

[Beagle]

if the 78 has a nine inch, you can probably just swap the center sections but I'd check the ratios first before swapping them. May have the same gear! Probably not. My 68 Ranger had 4.11's (240/3 on the tree) and it was SINGING at 70. The 78 may have 3.xx which would be worthwhile. As long as there is clean lube in the rear, it will last like the energizer bunny.

See Bruab's exploding driveshaft vids for what can happen when you run a long driveshaft too fast? U-joints and carrier bearings need inspection. The carrier bearing where the two pieces are supported in the middle went south in one of my old trucks, I swore it was brake noise. squeak squeak squeak.

[Deaf Bob]

Wouldn't F25o's have Danas? Or "14 bolt"
Admittingly, I aint a Ford guy... I don't think 9 inch came in F250's

[Loren]

Yeah, the F-250 ain't gonna have a nine-inch, there'll be something tougher w/ probably 4:11 gears. The ol' half-ton six would have a 9" with 3.00's. So anyhow, that original 9" in a light truck with an automatic will not likely have durability issues even with the V8 and you'd get a good highway gear, but if you wanna use the truck to tow or drag stuff out of the riverbed, swap in the one from the 3/4-ton.

Hey, so start w/ the 9" and if it blows up then swap!

[Huskinhano]

What's the diameter of the tire? Try this chart.

http://www.classic-cougar.com/tools/...speedocalc.php

[squirrel]

I have a 78 F250 4x4 parts truck. Would that rear end work if I needed it?

the F250 has 8 lug wheels, eh?

The 9" rear should be fine, but like any other mechanical part that's 40 years old, it wouldn't hurt to overhaul it.