I've installed some 25 steering racks over the last 19 years. Most of those have been on an MTX, although the one I did earlier this month was an ATX.
The electrical connection on your '90 rack is for the power steering pressure switch. Please go through anything I've written that you have already handled. I've included it so that I can add an article to Wiki SHO. So let me know of any corrections I need to make once you are done.
Inside the car:
Center the steering wheel and make sure that it doesn't move too much throughout the process.
Remove the kick panel from under the steering wheel with a torx bit.
Uncouple the steering shaft 1/2 way down and separate the two halves. 13mm IIRC.
Remove the dust boot. three nuts, 11mm.
Remove the pinch bolt at the bottom of the shaft. 10mm IIRC.
Jack up the car and put it on jack stands.
Remove the front wheels.
Remove the Y Pipe to access the hoses more easily. 8mm / 15mm / 18mm. 22mm for the front O2 sensor. No need to remove the rear one. Give the manifold studs plenty of penetrating oil. Work the nuts loose with your 15mm attached to a breaker bar and ease them back and forth. If really rusty, you might want to run an M10 x 1.5 die up the exposed part of the studs, and clean up the nuts when off.
If you have trouble getting the Y Pipe off, it's because the manifold studs have splayed. Once off eyeball the studs and bend back with a 12mm deep socket (impact preferred) on a long 1/2" extension bar. For complete accuracy, fab up one of these in thin sheet metal, two 7/16” holes drilled 3 ¾” apart as a template. Corner cut off to clear stuff:
If you have a cable shifter, disconnect the vertical cable and swing out of the way. 8mm.
Remove the two hoses, noting which hose goes where. 11/16". Although 18mm can work, you run the risk of rounding the nuts. Once loose, I use a shorty 18mm ratchet wrench to get them off.
Loosen off the locknuts between the inner and outer tie rod ends. 22mm. Use a white paint pen to mark the inner tie rod end just inboard of the nut so that you know roughly where the outers need to be positioned on the inners on the new rack.
Remove the cotter pins with a pair of wire cutters (lever them out).
Remove the castle nut from the end of the outer tie rod end. 18mm stock, some aftermarket 19mm.
Reverse the nut and reinstall on the tie rod stud such that it is flush with the bottom of the stud.
Use a 5 lb. hammer to whack on the knuckle around the outer tie rod to loosen it. GENTLY tap on the nut to see if has loosened. The nut is there to protect the threads. If not loose, repeat the process.
Remove outers from inners. Remove lock nuts from inners. Makes removing the rack easier, and probably need transferring to the new rack, anyway.
Remove the nuts holding the rack onto the subframe. 24mm.
Position a jack with a wooden plank on it and put it under the oil pan to hold the engine in place.
If you have the original rubber subframe bushings, remove the rear subframe bolts (18mm) and lower the assembly on to jack stands. You need to come down around 3". No need to touch the front subframe bolts: there should be enough flex in the bushings. Might also be the case with solid subframe bushings.
HOWEVER, if you have to loosen off all four subframe bolts, the whole subframe will shift, throwing off the caster and camber. In that case, use your paint pen to mark around all four bushings before touching the bolts to get it back where it was.
Raise the rack off the subframe and remove it via the driver's side wheel well.
Now take a look at the pressure port. You should see a domed jiggle valve in there. If what you see looks the same as the return port, it's fallen out somewhere.
Put the old rack side by side with the new one. Taking measurements, make sure that the new one has the same amount of inner tie rod end sticking out each end as the old one. Transfer the studs over. Transfer the pressure switch over. You might need a new rubber O ring.
If your new rack doesn't have a jiggle valve, transfer from the old one. If a pencil magnet doesn't remove it, it's being held in place with a washer that also needs to be removed. Install in the new rack, domed end facing you.
Peel back the outer dust boot end that's over the inner tie rod ends. Grease that area and put back. This will stop the dust boot twisting when turning the inner for toe alignment.
Installation is the reversal of removal....
100 ft. lb. on the 24mm rack nuts.
Subframe bolts, 85 ft. lb. If you had to loosen off all four bolts, reposition the subframe according to your paint marks. There are holes in the subframe and body just behind the front bushings to facilitate this.
Outer tie rod ends, 34 ft. lb. then turn more to line up the cotter pin hole. 1/8" x 1" pins.
Install new Teflon O rings on the hoses. 388-898-S from Ford. Aftermarket available, but I don't have the part number. Dribble a little power steering fluid over the hose nuts and work them back and forth. Makes turning them by hand easier. Don't over tighten them. The hoses are supposed to rotate.
Anti seize on the O2 sensor.
Front Toe alignment: a lot easier if you have wheel dollies you can put under the front wheels. If not, roll the car back and forth to settle the front wheels. Make sure that the steering wheel is dead center throughout the process.
Horizontal white paint line on the front of the front tires, below the level of the body. Makes it easier to distinguish between the front and rear of the tire. Sight along the tires. The wheel has the correct amount of toe when you can see around 1/4" of the rear of the front tire just as the rear tire disappears from view. Once done, you might want to have them professionally aligned. Toe should be zero. You will have noticed that the inner tie rod ends have flats for a wrench, or are serrated for pliers.
