Proper disassembly of Steering Gearbox - Page 4 - Mercedes-Benz Forum
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post #31 of 36 (permalink) Old 04-25-2019, 07:56 AM Thread Starter
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FULL DISCLOSURE: I used the following tools/techniques when I rebuilt my Power Steering Gearbox but I freely admit that I was less than perfect. My results are good, but not perfect.

I took the steering shaft coupler off of my parts vehicle last Summer and kept it on a shelf in the garage. I ground off the pressed bolts of the gearbox end of the coupler so that I would have the piece that fits onto the gearbox. The bonus is the two holes allowed me to bolt that piece onto a wooden ruler later. Next I took a wooden ruler that has both centimeter and inch graduations. I drilled a 3/4" hole dead center at the 15cm mark. Line up the coupler piece to the hole and marked the two holes onto the ruler. Drill out the two holes and bolt the ruler to the coupler.

Use an inexpensive kitchen scale to weigh out the sockets/nuts/washers/etc you use for measuring torque.

I drilled three holes in my (old) workbench so that I could bolt the gearbox securely. Use the three bolts that hold the gearbox onto the vehicle. I used various sockets for shim when bolting to the underside of the workbench. This allowed me to loosen and torque the various pieces as required.

Be careful of the teflon seal. I tried my proven technique of placing the rack gear with new teflon seal installed in the refrigerator to "shrink" them down every so slightly. It did NOT work this time. I damaged the teflon seal while pushing into the gearbox case. Very sorry to say that I ended up using the old teflon seal.

Here are some useful links:

How to reseal a MB steering gear

What a feeling it will be! A properly adjusted W123 / W116 / W126 power steering box - PeachParts Mercedes-Benz Forum
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post #32 of 36 (permalink) Old 04-25-2019, 08:47 AM
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I am very familiar with both procedures. My question is: How did you replace the teflon rings inside the piston? Hint: to do that you need to take the worm shaft out w/o loosing the balls...
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post #33 of 36 (permalink) Old 04-25-2019, 09:52 AM Thread Starter
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Originally Posted by liviu165 View Post
I am very familiar with both procedures. My question is: How did you replace the teflon rings inside the piston? Hint: to do that you need to take the worm shaft out w/o loosing the balls...
Liviu165,
I turned the steering shaft fully clockwise which pulled the rack tight against the bearing cap keeping the balls inside and untouched. Then I removed the steering shaft with the rack gear assembly attached. The working piston, worm gear and ball bearings are removed as a unit. This is steps 9 and 10 of the write up by David Petryk in the second link that I provided.
I needed to do a better job putting that unit back into the gearbox case. Unfortunately, I didn't slow down enough to triple check every step the first time and I allowed the new teflon seal to get pinched. On the second try I used four longer bolts on the bearing cap to very slowly pull the module into the gearbox case while carefully adjusting the teflon seal as appropriate.
As you have already figured out I may end up doing this job again if a leak develops. In the meantime I will rebuild the gearbox that came out of my parts vehicle so that it will be ready to go when needed.
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post #34 of 36 (permalink) Old 04-25-2019, 10:49 AM
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This is steps 9 and 10 of the write up by David Petryk in the second link that I provided.
David's procedure (first link, not second) is an excellent one to be considered as a starting point, but in all fairness is a bit "loose" by comparison with the FRM. As the picture shows, extraction of the worm shaft out of the piston is possible and there are no balls that came out (take my word that I did not hide them). Inside that piston are some sealing rings (I think 3 of them) that can be replaced. The white tube is just a PVC one from Lowes, that's the only "tool" needed to replace those three seals.
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post #35 of 36 (permalink) Old 04-26-2019, 12:22 PM Thread Starter
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Liviu165, is there a procedure that I should follow when extracting the worm shaft out of the piston? I don't want the balls dropping onto the floor. I am going to use this opportunity to rebuild the extra gearbox that I have so that it is ready for future use. Thanks In Advance, Tom
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post #36 of 36 (permalink) Old 04-26-2019, 02:11 PM
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To extract that worm shaft out, I made my own procedure. You are welcome to follow it.

I measured the diameter between the bottom of the groves of the shaft and looked for something that was slightly bigger than that, but it can deform a bit. The best I could come up with was a plastic tube from Lowes, I think is from the Plumbing or Irrigation department: a PVC tube.

Rotate the shaft out of the ball cage till you see the first ball appearing. Stop and put the PVC tube with one end against the end of the shaft (but-to-but) with NO space in between. With one hand hold the tube and with the other hand hold the shaft, pushed one against the other.

While you keep both pressed but-to-but, a second person will rotate the entire piston which will transition from the shaft onto the tube. After few inches of travel the entire piston will be only on the PVC tube and the shaft will be released. Replace the hidden o-rings inside and then proceed in reverse order transferring the piston back on the shaft. I found it very beneficial to hold the tube against the wall next to my bench (first picture) and I pushed the shaft against the tube.

Because the OD of the tube is slightly bigger, the the balls will make groves on the surface of the tube which you can see in my third picture. The whole idea is to slide something inside the balls cage as the shaft gets out so the balls will be kept in place and not fall off

I've done it twice and it worked fine, but I had help each time because two hands are not enough.
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