My plan is to swap out my front axle on my '71 F-250 4x4 with one out of a '75 to '77 1/2 or there abouts to gain disk brakes! Spring perch measurements should be the same I think and the steering I believe is the same? Simple upgrade as far as I can see what do you guys think?

 

You probably should change the rear axle at the same time. You will need matching ratios when you put the truck into 4wd.


John

 

Or Find one that is already has 4.10's (to match my existing rear) that was my plan and it would save time and work? Since they are both dana 60's in the rear I wouldn't be gaining much swapping them out?? Just the front I was just asking if anyone knew for sure if it was a direct bolt in swap, to the best of my knowledge they are interchangeable.

 

As I recall, yes. There were a few differences in steering design on different models from what I've run across in the wrecking yards, but you should be able to match it up easily enough. Be sure to get the correct disc brake master cylinder and proportioning valve to go with the disc brakes.

 

Dang Dan, They done give you a rank raise to super?? Are you getting anymore in in your pay envelope?


John

 

You know how it is John...nothing plus nothing still equals nothing!

 

The 75 dent still used drum brakes, and the first discs were in 76. This is a rather rare front axle, and finding parts can prove to be difficult. These also used a slightly different steering assist unit. There were two available. Be aware that the NP203 case might have been used, so there is a chance that you will have to add manual locking hubs.
Unfortunately the 76 front axle was still a low pinion axle. Same used in the 77, and not the 77.5.
The 77.5 was the first to use integrated power steering and a high pinion front axle. This was because the transfer case was now a married case and the driveshaft angle needed some help.
This high pinion front end is much stronger than the low pinion unit and parts are a dime a dozen. This will be a bolt in swap with the exception of the steering.
Perhaps this would be a good time to ditch the power assist and convert to real power steering?
Spring pad widths are the same, so this is not an issue. Your old Garrison power assist can still be fitted to the later axle if you choose to keep this. The later D44 arm can accomodate the drag link.

As for the rear axles, the slightly later axle is more desireable because it is slightly stronger. This is a 30 spline axle, and the early one is a 16 spline unit. Still a bit weak, but the 30 spline is stronger than the coarse spline unit.

 

No power steering on my 71 and thats the way I want to keep it, it does have power brakes but drum style of course! I think I'm sticking to the old low pinion 44 cause its not for wheelin or off road just my eneryday driver! I could put a 60 (actually have one sittin out here with 4.10:1 same ratio as my 71) in the front I have a couple around but want the steering to stay oem and the drive shaft to stay the same! I just thought that 76-77.5 front axle would be a bolt on disk brake upgrade! I think even the trucks with the power assist are the same setup as far as steering goes I would just have to remove the hydraulic ram? Pitman arm on the 76-77.5 is the same length isn't it?

 

This is interesting. Should you choose to keep the manual steering, then I do not see why you could not use your straight and solid drag link from the early truck.
The hydraulic assist ram is only a bolt on device and comes off easilly. This will leave a hole in the tie rod, but this can either be left alone, no issue, or replaced with the older one that simply does not have the hole.
The manual drag link will have enough adjustment to straighten the wheel if the pitman arms are slightly differnent which I do actually believe they are. The 76 truck had a slightly longer pitman arm that corresponded with the Bendix sterring and control valve.
Heak, I even suppose that you could even use the control valve dry, and it would work like a regular old drag link. Easy enough to make one too, but the original manual drag link should work too.
The steering arms on the knuckle will put the drag link in about the same spot, so there should not be much of an issue there as well.
Sounds like a reasonable swap, for your application.

 

I belived the frame rails our wider on the 75 or 76 and up 71 is like 43 and later 53" so our the axle spring pads. I was going to do the same disc brake upgrade and found i think a 75 that had dic brakes and and narrow frame but didn't want to mess with power asist setup. So passed it was low pinion with dis-brakes..
orich

 

Only the rear frame rails are wider, the front is the same from 67 to early 77. The 77.5+ has wider rear frame rails to accomodate the between frame gas tank.

 

To my knowledge I think it will bolt right in. The simpler the better and thats why I don't want the power steering/assist. I like the "Old grain truck" feel of it!!! I figured someone here had already attempted this or accomplished it? I cant see a reason not to do it the closed knuckle setup is just not a good design in my opinion I like ball joints, really like trunion's,and having exposed axle joints! But no 60f for this rig it just doesn't need it (I think thats the first time I've ever said that!) so therefore no trunion (not sure on the spelling of that word?) Thanks for the knowledge!

 

jhooch, I believe if you will go back for another look you will find the fronts the same from 65 to 79, and the rear was widened in 73 to allow the rear track to match the front, allowing the gas tank to be placed between the rails as stated.


John

 

I think the front frame width is close within 1/2" at least from 73-79 reason I say this is I had a early '77 F-250 that I had 46" baja Claw tires on and it only had a dana 44 in the front I obviously needed to put a 60 up front so I started doing the measurements and it looked as though the spring perch's were real close but the steering was going to need modified (Changed to crossover) but then I sold the truck and never finished the project!

 

73 to 79 front frame dimensions are identical. Bumpers and spring perches share identical dimensions. Front axles (for any F250, and even the 79 F350) will be direct bolt in interchanges.
The only frame width difference is after 77.5. The rear of the frame was widened to accommodate the inboard (dual) gas tanks. These share the same widths with the 2wd trucks.
Front dimensions are exactly the same, your axle will bolt right in.