will fit in my 66 F100 without relocating a bunch of stuff? It presently has a dana 44 with 3.54 gears , but i want to add a C6 and lower the ratio to 3.08 for highway driving, by going to the wide ratio C6 i think my off the light speed will be ok also. so insted of regearing the dana im leaning toward going to a 9"

 

The F100 9" has a flange to flange width of 57" It was used in F100s from '58-'72, so there are tons and tons out there. Going rate were I live is $100.

 

Comet is right on, 57-72 9"s will fit. There might be some brake line differences, but nothing that can't be easily worked out.

John

 

Java,
FWIW, I just threw the Dana under my 88 F150 out and put a complete 9" form a 77 under it eliminating the stupid intermittent ABS, and all the Dana problems those rears tend to get. It was the greatest improvement I've done to that beater/ shop truck.

73-79 rears will also fit but you'd have to do the mods you do not want to do. But

IMHO, better center sections exist in 73-79 rears. Those center sections will bolt into 57-72 axle/rearend housings. I say better because they come with ratios more popular in todays world. 2.78, 2.90's 3.00's and 3.25's were more common in the 73-79 trucks than the earlier ones. So were 4-pinion spider gear set ups, more traction aid devices, and bigger/ better brakes. Most of the stuff can be interchanged between both year groupings of 9" FoMoCo truck rears.

Here's a helpful hint on draining the 9" reasr that lack a drain plug. loosen the bottom most nuts so they are only hanging on the studs by a few threads, then tap them back toward the carrier housing, the studs will pop off of their splined seats and the gear oil will drain out, a bit slow, but. . . it's better than the rush of gear oil you'll get if you don't drain the non draining rears when the carrier housing is broken loose.

If you don't care about the axle housing, or if you plan to yank the carrier housing anyhow, take the nuts off completely and bang the studs right thru into the axle housing. It will drain much quicker that way, just remember to remove or replace the studs before you re-install the centersection/ carrier hsg.

FBp

 

A couple other things to remember on the '73 and up (through '90 at least) is that the axle is 1.75" wider than our vintage. Also, Ford widened the frames (I can't remember if they did it in '73, but I know they did it in '77 1/2. I get 4x4 stuff confused with 4x2s and the Highboy is a different frame), so the spring perches are wider and would need to be moved or some other way addressed.

 

I do believe 86 was the last year for the 9". The 8.8s had been introduced by then in some trucks.

John

 

If you use a rear axle from a '68 - '72, you will not have to make any modifications at all, and you will be able to use the wider rear brakes. Be sure to use the existing parking brake cables, though.

 

I wasn't exactly sure myself, so I went to a Ford 9" web page that said F150s had them until 1990 I thought that was goofy, but that's what it said, so I used it.