Saginaw Box Rebuild - How To! (Link to source)

Thanks to everyone that was patient. Flame away! The particular model I will be rebuilding is a “Model 83”- as noted by the raised numbers that can be found in the forged housing. I am unsure of all of the available years that Chevrolet used this box; however, I believe they were on every ½ ton from 88-98. The larger tonnage (3/4 ton and 1 ton) used a heavier duty box – Model 84 – that consisted of a larger housing and larger internals; the premise is the same though. Here are all the internal components of a power steering box. From left to right: end cap, power piston with sector shaft sitting on top, worm gear, and input assembly. The box is in its proper orientation (meaning the things in the left of the picture fit into the left side of the box etc).

These are the two locations for tapping a steering box. Look at Billavista’s article in the Tech department for more information.

The internal components fit together in such a manner that they operate as one unit. Here is how once inside the box, everything will look. *Note that between the base of the worm gear and the front of the power piston is a wall inside the housing. So in fact, these two surfaces will never touch – this picture is just for the effect.

First remove the retaining collar by turning in a counter-clockwise motion. Vise-grip pliers or the like can be used, but I prefer a punch. Once loosened, it threads off very easily.

Next mark-or count- the number of threads that can be seen on the front of the input assembly plate. This will insure the proper preload is applied to the assembly, and does not require the purchase of a spanner nut to set the proper torque. After marking the threads, remove the plate by turning counter-clockwise. The proper spanner nut makes this easy, but improvisation gets the job done as well. You can use a punch as pictured here, or an easier way is to find the proper Allen head wrench that will just fit into the hole. Align it so the force is tangential to the plate and loosen away with a hammer to the base of the long end of the wrench (sorry I did not get a picture, I thought of this method later).

This is what you will see after removing the input plate. Now pull out on the input piece (grabbing onto the splines is the easiest way to get a hold of it) and slightly twist as you pull.

After removing the assembly, you will see the head of the worm gear in the housing.

Here are the three parts you have removed so far: the retaining collar, the input plate, and the input assembly itself.

Here is a closer view of the input assembly.

The input assembly consists of four (4) main components, some of which have seals that must be replaced in a rebuild. For simplicity sake (and because I have no idea what each part is properly called), I will name the parts as following (from left to right): Part A, B, C and D.

Part B simply slides off of part A by pulling towards the splines.

Here you can see the seal and o-ring that must be replaced. Some rebuild kits include a replacement bearing for the one located behind this outer seal. After removing the seal, gently press out the old bearing with a socket and hammer and replace it with the new one. *Be careful however, as this part actually consists of 4 or more parts. Too much force trying to remove the seal can cause part B to disassemble and I did not get pictures of putting it back together. Although, don't worry it can be done.

To separate the remaining components from part C, simply push on part A (from the splined side). This will force the remaining components out the back of part C.

If part D does not come out with part A – simply put a socket onto the lip of D and hammer it out. Here you can see its location.

Part A and D fit together as shown here. Note the small nipple on part A that fits into the hole in part D for proper alignment. You can also see the o-ring at the top of part D that must be replaced.

Here is part C. You can see the three Teflon o-rings that must be replaced. Also, underneath these three o-rings are three more o-rings (brown) that must be replaced as well.

So after replacing all the o-rings and seals for the input assembly, place the components back together as follows. First, place part D onto part A aligning the hole/nipple. Next, slide part A and D as a unit into C with plenty of power steering fluid as a lubricant. *Note: Part D might not want to go in very easily and the nipple/hole might slip out of each other. Keep trying it will go in.

After partial insertion of unit A and D into C, make sure to align the tab with the raised area pictured here. You can turn the unit once it is somewhat recessed, so you do not have to worry about lining it up from the very beginning.

Now slide part B back onto the shaft of part A and set the whole assembly aside for later. Mark –or count- the number of threads located on the top plate adjuster nut. This nut determines the backlash between the power piston teeth and the sector shaft teeth, and thus, the return to center characteristics of the steering. By marking you will be able to get stock characteristics, and do not risk the chance of binding/disengagement of the teeth due to improper backlash. After noting the threads, use an Allen wrench as a backup, and loosen the nut by turning counter clockwise.

Next removing the four nuts holding the top plate onto the housing. Then, back the top plate off the sector shaft using the Allen head wrench while holding the top plate with the other hand to keep it from spinning.

First the end cap will pop off.

Followed by the power piston. *Note: All of the remaining ball bearings (those that did not fall out with the worm gear) lie inside the power piston. Make sure to not invert the piston until you have a hand underneath to catch the remaining balls. There should be a total of 24: 12 light and 12 dark. Count to make sure all are accounted for before continuing.

Remove the dust boot from the sector shaft output area.

Remove the outer seal.

Remove the snap ring and the washer that is behind it.

Now you will see the second seal, and the bearing behind it.

Here is a view from the top plate area looking into the housing. You can see the bearing as it is pressed. It is here, the socket will be placed.

Using a long socket and a hammer, flip the housing over and press the bearing and socket out together as one.

Most rebuild kits do not include a new bearing for the sector shaft. However, if you want, going to a hydraulic store and having one special ordered can be done; though most of the time, it is not necessary. As with any rebuild, use intuition as to whether or not your parts may need replacing. The sector shaft bearing and inner seal.

Now that you have the housing completely bare, you can drill/ tap the holes as needed. Once done, clean the housing very, very thoroughly with a solvent to remove any metal contaminants from drilling. If you did tap the box, use compressed air to clean the ports that the fluid will flow through. Also, clean all of the components very well in order to determine any damage done, and to ensure trouble free running later on down the road. Lubricate the inside of the housing liberally by smearing power steering fluid with your finger. Now you are ready for reinstallation of the internals. First replace the sector shaft bearing by pressing it back into the housing. Note the lip on the top of the bearing and where the ridge exists inside the housing. Press until full contact is made.

A picture of pressing the new bearing into the housing.

Please note that for simpicity's sake, I just took the pictures by reusing the old parts. The new parts should be used at this time. Follow that by the new inner seal.

Then by the new washer.

Then by the new snap ring.

Then by the new outer seal.

And finally, by replacing the dust shield.

The worm gear is a machined piece, with two washers and some needle bearings sandwiched between the washers all located at the gear’s base.

Inspect the bearings for damage and replace as necessary. Clean the washers and worm gear, and slightly lubricate for reinstallation.

Here you can see the input assembly and part A from earlier recessed into part C. Note the location of the two tabs machined out and how they match the head of the worm gear. Also, replace the brown seal located at the end of part A. Place the two pieces together making sure to align the tab on the side of the worm gear, with the proper hole in part C.

Here you can see how the input assembly and the worm gear fit together. Install this one piece back into the housing from the input side.

Replace the input plate and tighten it until the marked thread position from earlier.

Replace the retaining collar over the input plate.

At this time, try turning the input assembly shaft with your hand. It should turn freely with some resistance. If it is impossible to turn, or turns too freely, make adjustments to the input plate by threading it on more or less. Getting the proper preload onto the bearings and input assembly o-rings is essential as it must withstand thousands of psi of fluid at times. Make sure you are comfortable with the preload and then continue.

Here is the view from the base of the housing thus far. The metal tip you see is the end of the worm gear as it sits in the side of the housing that contains the power piston.

Next, lubricate the power piston liberally (after replacing the Teflon o-ring) and slide it back into the housing.

Rotate the piston by hand (or by prying with a screwdriver or the like)like so:

until this is the image you will see. (Note the location of the two holes entering the machined channels).

Clean and separate the two types of ball bearings into their respected groups (light and dark).

Locate the splines on the front of the input assembly. Rotate until the flat surface with the hole faces up (in line with the port holes). This is the center position for the box, and will line the worm gear up accordingly.

Place the first ball (light) into the top opening into the machined channels of the power piston. As you can see the ball will rest on top.

Lightly tap (just by using your hand on the punch) the ball into the recess with a punch. The ball will drop out of sight as it falls into the channel. Place the next ball (alternate between light and dark)into the same top hole, and repeat until only six balls remain. *Note: As you are tapping the balls into the channel, you may notice the power piston slightly moving. This is expected, as it is setting the piston to its center location (to match the worm gear at its center). Just make sure the worm gear stays at center (flat part on the splined surface stays up) and everything will be in the proper position.

After tapping the ball into the channel, it will look like it did before.

Once you have all but 6 balls into the machined channels, you will no longer be able to place anymore inside. Now, you must place the remaining ball bearings into the removable channel (make sure to alternate). Be sure that the side with the dark ball first goes into the machined channel with the light ball showing).

Then carefully slip the removable channel into the top and bottom holes. I find that if you slightly bind the channel pieces by holding the piece betwen a thumb and finger and slightly pushing forward on one piece while holding the other, that the balls do not have a chance of falling out. Try this method (I always get it first try) before using petroleum jelly or the like to secure the balls.

Gently tap on the removable channel to ensure proper seating, and then secure it with the strap and two bolts.

Rotate the power piston (by hand or leverage device) until the teeth are parallel to the box.

Replace the cleaned sector shaft by sliding it into the housing, making sure to engage all the gear teeth. The sector shaft should be able to move from the front of the power piston teeth to the rear without much force. If too much pressure is required, remove the sector shaft and try rotating the power piston slightly until the sweet spot is found. Making sure everything fits nicely here will eliminate chances of binding/disengagement later.

Replace the gasket for the top plate by bending the retaining clips on the gasket around the plate.

To put the top plate back onto the sector shaft, simply thread it on by using the wrench while holding the plate with your other hand (to keep it from spinning).

Replace the four top plate mounting bolts and tighten.

Using the same method of removing the top plate adjustment nut, place the new nut onto the splined sector shaft and tighten until the proper thread count from earlier is achieved. You may have to thread the sector shaft in/out (by using the Allen head wrench only) to get back towards the proper thread count. If you look closely as you turn, you can see the splined end of the sector shaft moving.

Replace the o-ring around the end plate, and press the plate into the end of the housing. It will be recessed enough, once the groove for the new retaining ring is visible all the way around.

Place the new retaining ring into the groove.

After everything is reassembled, rotate the input shaft from lock to lock. The shaft should turn 1 1/2 times to the right, and 1 1/2 times to the left from the center position. If any binding occurs, it is between the sector shaft and power piston teeth. If you are sure the power piston was level, then adjust the sector shaft by turning the loosening the nut and turning the shaft with an Allen wrench. Test for binding after each 1/2 turn or so. That concludes this how-to. I hope it helps out those of you that are contemplating tapping a box by yourselves, as it is a fairly simple process. If something does not make sense, or you would like a further explanation in an area please let me know and I will glady edit it until all questions are answered. Also, if I got something wrong, I apologize and will gladly fix any information. I know it does not have a lot of extra tech, but I hope it gets the job done. Thoughts?