So I am in the process of upgrading the steering in my f100 so here is how I did the first step of obtaining a gearbox...

I pretty much followed the instructions these guys have posted on the internet: http://www.wcb4x4.com/tech/diyrockcrawler.shtml

That should simplify everything but thought I would add my flare to it.

Here are the two gearboxes I started with. The one on the left is from a 78 bronco and the one on the right is from a 90 bronco ( not 100% certain on the year but its the right box).



Before I started this conversion I took both boxes to a shop where they let me break the torques; glad i did as these this are hrld together pretty well. This is the newer box before I broke it down.



Here is the 78 box from a couple angles.




This here is the sector shaft coming out of the housing. It was critical the clean the splines where the pitman arm goes so the dirt doesnt destroy the seals when you pull it through.



78 box sector shaft out.



A top down look into the box with the shaft out.



Spline housing out... As the instructions state - do not let the worm gear or any of the other stuff spin or youll jack everything up. It really wants to spin though so be careful. A little movement seems inevitable but keep it to a minimal amount.



78 box housing with everything out. I though the pressure fittings might wind up on top when this was complete but do to the port which runs though the housing this was not the case; ports end up in the same place as the original input housing.



Here is why you want to clean that sector shaft before yanking it though the seal. This pic was from the newer box so i didnt give it quite the attention as with the 78 box; its going in the scrap heap once this is done.



The sector shaft comes out of the newer box the same way.



I drained both boxes the best I could but you still want to be careful of messes.



Reversed input removed.



Slapping the newer box back together.



I even stole the hardware from the donor box; I figured 15 years newer meant it would give back that many more years. I liked the shape of the heads better. Not sure when these went metric or if they went metric but if they did you will have to reuse the old or buy new.





Back to the 78 box... Cleaned it out a little better.



Going back together...



Reversed input in... Be sure to center for the sector shaft.



Sector shaft goes right back in...



Pitman arm goes back on 180 degrees out from where it was; essentially pointing straight back.





This part if my steering conversion was pretty straight forward. I hope the rest continues to do so.

The only slight area of concern was a small amount of binding during the ops check. A tiny bit of tweeking the adjustment screw seemed to fix this but resulted in an almost unnoticeable amount of play in the box. Compared to the play I currently struggle with I dont think this will be an issue. I will be sure to readjust once my new box gets worn in a little.

The only thing left besides the install is a good degreasing and some paint.

 

Nice write up! I quickly scanned thru the link too. Along with a quicker ratio what are the benefits? Just a basic re-seal kit?

Thanks for taking the time to photo document the conversion! Major in-advance help!!!

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The seals checked out ok so I didnt replace them... Special tools seem to be needed to do so. My objective is to replace my factory power assist and manual gearbox. The problem is there are no bolt on replacement gearboxes to do so; this box is the closest thing but the pitman arm faces forward when I need it to point backwards. If you simply bolt the pitman arm on backwards it will cause the truck to steer left when you turn right; not a good thing. Installing the reversed input gear as indicated corrects this. The box is essentially ready to install although the bolts do still need torqued.

So in terms of benefits: it will turn the right way, it only cost $70 @ pick n pull vs $1k or so from some of the shops that do the same thing, and I will have power steering when done.

This was pretty straight forward. Busting the pitman arms loose was the hardest part as they are not meant to fall off.

 

Thought I would elaborate slightly on what I am replacing. Here is the pic: