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RadioTek 10-05-2009 10:52 PM

Oh, @#$%. Steering gear box removal on a 107
Trying to replace the completely worn out steering coupler on a '75 450SL. The rubber bushings are completely gone, the steering wheel is sloppy.

Got the 6mm allen head screw out on the steering wheel shaft with little problem. Was able to get to it by removing the cover at the base of the steering column and applying PB Blaster liberally. A sharp twist, and it was loose.

Now to get the one on the gear box. No such luck. Had to get to it from underneath the car, but the damn allen head screw rounded out with out moving the bolt. I think I have to drop the gear box to get to that one and get creative with an Easy-Out and/or Vice Grips, if not a drill press. :mad:

Does anyone have any suggestions or tips before I go in there? I'm pretty sure I have to get the Pittman arm off the gear box, at least. Do I have to get the tie rods loose as well? I just don't want to have to buy too many tools that I won't use again.

Does anyone have the thread pitch and size for the bolt I need to make the gearbox immobilizer tool with?

Any help greatly appreciated.


Roncallo 10-06-2009 07:34 AM

You are very luck that you striped the one on the box side so you can take it out and work on it.

Remove the steering gearbox with the pitman arm installed. The pitman arm is very difficult to remove, and you dont need to remove it to replace the steering coupler. However once you have the box out it would be a good idea to replace the input and output seals. The output seal is the one that usually leaks and will require removal of the pitman arm.

The trick to pitman arm removal is a really good pitman arm puller "Snap-On = $120.00" or like I did with a cheep puller and PB blaster and a few days of tightening and whacking with a large hammer.

When you are ready to put it back in buy 2 new coupler screws from your MB dealer. These replacement ones will be torx head and will not strip.

Mike D 10-06-2009 08:02 AM

Also replace the gear box mounting bolts with new hardened bolts. Do not re-use the old bolts.Torque the bolts, don't just whale on them with an impact wrench. Now's a good time to inspect the rail mounting area for any rust or collapsing issues.

The centering bolt can be made using an 8 mm standard thread bolt. Grind the very tip of it into a cone and it will fit into the dimple on the gear box shaft.

meltedpanda 10-06-2009 11:44 AM

wait - dropping the box will be a major PIA, any way to tac weld to the stripped bolt ?
I have spent many hours in the last weeks doing the job you are doing now, fortunatley mine did not strip. Can you drill it out, the coupler is trash anyways - and there is room to avoid the spline.
Good luck

RadioTek 10-07-2009 12:01 AM

Unfortunately, it's the bolt closest to the gearbox. The one you can't really see from inside the car.

If I could figure a way to get an Easy-Out of the appropriate diameter and length, about 18 inches long, I might be able to do it from underneath without dropping the gearbox. My life doesn't work that way.

If I don't have to pull the Pittman arm, I can just pull the drag link at the 'outer' end,right? Do I need special tools to separate the end on that? Or would a set of those Harbor Freight tie rod removers be in order (not the pickle fork)?

I've got tie rods, drag link, and steering damper already, as I'm accumulating parts gradually before I take it in for the subframe recall. I figure I can get the same parts online for less than the dealership would charge.

Any and all help is greatly appreciated. I will go in to the dealership for both new coupler bolts, though. I have a source for the other bolts needed, like the mounting bolts and the one I need to make the immobiliser. How long does the bolt for that have to be? How far inside the gearbox does it have to go?

If that one bolt had not rounded out, this would have been a nice job, but noooo:eek:


meltedpanda 10-07-2009 02:22 PM

I am assuming you have the car on blocks, I still say with a proper bit you should be able to drill it out, wear eye covering and drill it until it lets go??

Billybob 10-07-2009 02:43 PM

External Bolt Extractor?
Assuming there is enough room around the outside of thge cap screw's head a very viable option might be the external type bolt extactors. You can pound one into place over the fasteners head and then use a ratchet and extension to turn it off. Using a penetrant spray and maybe even some heat on the threaded section will usually encourage things breaking free.

Here's the tool as its available from Sears but there are similar tools made by Irwin and Hanson that are available at Auto Zone and the like. Good luck! QqqiIyVlZDWUfGsj4GAO6v73I8lL%0A8NfdJRZfxPR%2BDTEPwvIT0PaXy81OX9%2FjXjW%2Fy2kDzr%2BaN2qOdcKotRQ6VKQZu CGFu7IKyu34WxeU%0AGcE8tk4q91qFa90MM8PL6vHX7EBLfw%3D%3D

meltedpanda 10-07-2009 04:07 PM

when I did mine, from underneath I could rotate the coupler until the bolt was in easy sight and easy to get a wrench on, it this your case? Yes my wheels were on blocks and a bit sideways. Had other supports, just in case...

Genbiltstein 10-07-2009 07:24 PM

Lets get some pictures and see what you are faced with if you can.

RadioTek 10-08-2009 01:07 AM

Of course I have it up on stands. I'm too old and fat to get under one of these things without them. :D Imagine if you will... A roughly cylidrical opening about 3 inches diameter and about 12 inches long. At the top is the coupler: easy to see, but only reachable with LONG tools. My hands are HUGE, I have to use the XLarge nitrile gloves, and they are stretched, so getting in there to work on it is going to be ...problematical...

I wonder if those bolt/nut removers come in a size sufficient to drive on and turn? I'll have to look, it seems a possibility. If I hit it with PB Blaster for a couple days, I just might get lucky. I'll check out my local NAPA store, There's a guy there that has helped me with other stuff before on the '55 Pontiac.

I just hope I can get to there tomorrow, I've put some long days in at work this week so far.


tan man 10-09-2009 04:47 AM

I am confused by your initial post - is your main objective to replace the steering coupling or the gear box?
If its just the coupling and you got the upper allen head bolt off then try this for the lower bolt: the correct angle is the key. using your allen head bit with extensions get to it from the top by the firewall. Have someone give slight turn on the steering wheel till you get the straightest angle to push the allen head bit in the bolt. You will not be able to do it entering from near the brake booster, it will have to be almost a straight down angle from the center. Once you've seated the allen bit as best you can, give the extensions a few whacks with a hammer to fully seat the bit all the way in. Now try turning the bolt out.
These allen head bolts fill up with dirt so that you sometimes can not seat the drive bit all the way in. The impression you get is that the bolt is stripped. These bolts are not that easy to strip, there are good sharp edges at the bottom of the bolt openning. Also, check the allen bit you are using - if it is old and worn chuck it and get a good one for $12 at Sears. That will make the difference. Good luck. If you get the bolt out you should be able to remove the coupler by just removing the 3 bolts that hold the steering gear box in place. The gear box should move enough to let you slide the coupler off and insert a new one.
If on the other hand your objective was to replace the gear box and you removed the upper coupler bolt then you should have no problem sliding the gearbox with coupler off the steering shaft spline. If you find it difficult to manuever then just loosen the steering wheel shaft, pull it up a few inches and it will come out of the coupling. I simplified the description, several things to be careful of like lining up the steering shaft so that your turn signals engage/shut off properly, etc...

meltedpanda 10-09-2009 10:19 AM

tan man is correct, the angle is critical , which is why i had my wheels adjusted such that the allen nut was most accessible, then I use a flexible extention and seated it befor turning. On my 450 , I could not access from the top side. They are hard to strip but possible, interestingly the new couplers use torx bolts ( 45 I think)
I may be crazy here , but if you completely remove the steering shaft out of the way( not the tube) could you not get a sawsall blade on that nut? Seems like I would have had enough room to do that .
Oh and make sure its an allen, if it has been replaced in the past it may have a torx bolt

rs899 10-09-2009 10:27 AM

One more suggestion, depending on accessability, that has sometimes worked for me is to give it a whack in the proper direction with a sharp chiesel. Sometimes the shock and spin is enough to spin them out.

RadioTek 10-10-2009 01:32 PM

Well, as soon as I get back from Harbor Freight with either a pickle fork or a tie rod end separator, I'm going in.

I've gotten 3 different types of extractor, 1 external and 2 internal, hit it with PB, and bought the new bolts. Both the ones for the coupler and the ones for the gearbox.

I'm going to drop it down off the stands in front to immobilise the wheels so the coupler isn't trying to move away from me while I try to set the extractors. I'll get out the camera and try to get some photos of the project if I can.

I've been contemplating a virgin sacrifice just as a preventative measure, but they're so damn hard to find..:D

Wish me luck.


Sheridan: Ready?
Delenn: Why do you humans always ask ready? before doing something massively unwise?
Sheridan: Tradition.

RadioTek 10-11-2009 01:06 AM

The story so far.... The external extractor won't work. No clearance outside to get it on. One of the internal types won't go in. One is too small, the next too big. Found one with a more conical shape and got it in and set. Gave it a good sharp twist and the damn thing breaks off in the hole.

Now in the process of taking out the gearbox to get up close and personal with this bolt. Of course, the parts guy at the store gave me the wrong thread pitch for the immobilizer bolt, so I have to go back in the morning. I was able to get the gearbox bolts broken loose with an impact socket and a 20 inch breaker bar (leverage is nice) though.

Going back under there in the morning. This time I'll wear my lucky mechanicing shirt, if it hasn't crawled off too far. :eek:

Not enough hands for the camera, yet, so maybe pics later.


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