Steering box.

[koan]

My steering is vague and wandery, have to work all the time to stay in lane, also runs off the camber. Had a couple of front end alignments that haven't done much to help.

There does seem to be a lot of play, more wheel movement is required than I would expect to get a perceptible movement in the front wheels. All the steering related joints have been replaced as well as the coupling which is good. 

When I first got the car the steering box was leaking, I got a repair kit and had an independent re-seal it, he said the box was in good condition.

I adjusted the sector gear mesh screw 1/4 turn out when I access (manifolds off), didn't seem to reduce the slack so I restored it to original position.

Are there any adjustable pieces in the box (apart from the outside screw) that could cause excess free play?

koan

[oscar]

Hi koan

I was reading your thread and was thinking about my own experience with povo.  I adjusted that screw a few times and all I got was tighter steering but no improvement in freeplay.   So I resorted to swapping boxes but before I did that, I wanted to know if there was something else I could do and after a bit of searching I remembered sclass doing a 6.9 box so I looked up all his info.  You may remember it or even already revisited it but he was replacing parts with good 280 parts. RHD to LHD but if you got a RHD box from the wreckers this might be the cheapest option for overhaul.  I'm not sure how it all ended up for sclass but have a look if you haven't already.


http://forum.w116.org/mechanicals/6-9-steering-box-overhaul/

[koan]

You may remember it or even already revisited it but he was replacing parts with good 280 parts. RHD to LHD but if you got a RHD box from the wreckers this might be the cheapest option for overhaul.  I'm not sure how it all ended up for sclass but have a look if you haven't already.

http://forum.w116.org/mechanicals/6-9-steering-box-overhaul/

I remember the thread but couldn't find it (never seem able to locate old threads), thanks.

It does sort of finish in the middle of the rebuild. I may have to contact him offline as invited for further info.

koan

[TJ 450]

I would have a very close look at the coupling, track rod ends, idler arm and drag link in that order. In my case, the main culprit was the coupling followed by the track rod ends. This added up to about 2-3" of play on my 6.9. Now it is well and truly within 1/2" just after replacing those components. The box hasn't been touched yet.

It would pay to check the front suspension bushes, too IMHO.

Tim

[s class]

koan, I did complete the rebuild and I got very satisfactory results.  I prefer not to post it all up on a public board as I am not comfortable suggesting to every joe soap how to do something - i consider it a pretty advanced repair procedure to get right.  I have no problem showing you though as I believe you have the abilities. 

Sad story though - the desktop PC at home with all the photos/description on crashed a week ago.  I have to scratch around to see if I have a backup of the stuff. 

[koan]

Tim - every part you mention in the steering and suspension has been replace in the last 10 years, less than 10k kms. Except the upper control arms, I retained the old steel units as I considered them good.

A clunk has developed in the left front on rough roads, need to look into that.

I'm convinced the problem is the steering box but have been wrong many times before.

And s-class anything you can find would be good as would any words of wisdom.

koan

[s class]

koan, I am quite willing to accept that your problem is related to the steering box.  Some 18 months ago, I went on a quest to buy up decent steering boxes to source components for my cars.  The local specialist breaker had about 50 boxes from 123's, 116's and 107s.  they share pistons and sector shafts.  I spent an entire afternoon adjusting the sector shaft clearance in every single one of these boxes, in an effort to identify a few that might be worth buying.  Not one of them was even close to useable. 

I got real lucky with the 280SE box I ended up buying.  It was a complete car that had come in, looking quite reasonable.  I could see that the sector shaft adjustment was well in, and since I could get the box for $50, I bought it in the hope it was good.  It turned out to be easily the best used one I've come across.  Sometimes luck is one one's side.

Before I did the final assembly, I did many mock assemblies with the various pistons and sector shafts I was considering using in order to establish if I could obtain a high point in the centre of the range of operation . Takes some patience. 

I removed the crown nut off the top of the 6.9's original piston in order to exract the large bore nut (to mate with the 6.9's large diameter carrier).  That is a herculean effort.  I had to custom modify a 3/4" drive socket to engage the dog nut.  About 6 feet of extension on the breaker bar was required to open the nut.  Reassembly is a real art, because you have to pretension the bearings just right, so that when the crown nut is torqued, the turning resistance of the recirculating ball unit in the piston (without input screw inserted) is within a certain tolerance.  the crown nut has some crazy torque - I can't remember correctly, but I'm sure it exceeded the 200Nm limit of my torque wrench.  I used special strain-guage based torque measurement equipment borrowed from a metalurgical metrology lab to set up the box.  The problem is the final torque of the crown nut is so high it distorts the piston, altering the preload I thought I had got correct on the bearings.

then there is the problem of inserting the input screw into the piston assmebly and installing the balls.  Some boxes I've stripped have 23 balls, some have 24.   

Clearly, this procedure falls in the category of 'don't try this at home' - I take no responsibility!

Setting up the turning resistance of the sector shaft also takes some sophisticated equiment. 

I have checked my archives, and sadly it seems I have lost for good all the photos of this. 

I am intending to send in the dead harddrive to a data recovery specialist to see what can be recovered. 

[koan]

Thanks s-class for an interesting read. Bits of it sound a bit nasty but I do like a challenge

What creates the centre high spot? is it the cut of the sector gear or piston or ...?

Is there any adjustment or shim selection in the box that could introduce freeplay?

I think I'll avoid the piston dismantling.

What's the problem with the disk?. Mechanical in that it won't spin up or file system corruption?

There are easy fixes for some mechanical problems contrary to what you might think.

koan
 

[koan]

Been looking at this 126 steering box rebuild pictorial (http://www.davidpetryk.net/Mercedes/Steering.htm).

I'm now a bit confused, no doubt it would make sense if I had the pieces in front of me but I don't - yet.

Is step 14 described as "Remove the lock nut on the steering shaft bearing cap. I clamped it in the vise and used a chain wrench to turn the bearing cap assembly. I would have preferred to use a wrench but I did not have one big enough" the same step as you describe s-class using the modified socket and the long extension?

link to associated image.

koan

[s class]

What creates the centre high spot? is it the cut of the sector gear or piston or ...?

I believe it is due to the cut of the teeth in the sector shaft.  See this photo :



The cut is designed that when new, and set up correctly, there is less clearance between the teeth of the sector shaft and piston around the centre, than when off-centre.  This is intended to give a nice precise steering feel when travelling at high speed on highways.

The problem is that over the years, wear results in these clearances increasing.  Inevitably, wear is most severe around the centre, since this is where th steering box is used most of the time.  The result is that one ends up with more free play/clearance in the central area than towards the ends of the range of movement.

The external adjuustment one can make at the top of the steering box (on the outside) pulls the sector shaft inwards slightly to reduce the clearance.  The problem is it decreases the clearance uniformly across the range of movement.  So in practice, only a very limited amount of play in the central region can be dialled out before you start to get binding at the ends of the range of motion where there is inherently less wear. 

Wear in these teeth is the primary cause of poor feel in the steering boxes.  You can buy new sector shafts, or new sector shaft/piston combos from the dealer, but they are very expensive - something like US$1000. 

I have come to believe that there is also a secondary cause of 'worn feel'.  I have found in some boxes a fair bit of end play between the central input screw and the recirculating ball unit.  I'm not sure where the wear in this area is.  It could be :

a) balls
b) central screw shaft
c) recirculating ball housing
d) combination of all three.

In anycase, the effect of this is much less of a problem than the wear in the sector shaft and piston teeth, but obviously all sources of play need to be addressed if one is wanting a completely 'new feel'. 

Is there any adjustment or shim selection in the box that could introduce freeplay?

No.  Not that I can see. 

What's the problem with the disk?. Mechanical in that it won't spin up or file system corruption?

There are easy fixes for some mechanical problems contrary to what you might think.

I'm not sure, I thought it was boot sector corruption, but I have tried the disk in a linux box and even there it simply can't see the disk even exists.  I'm fairly confident something can be recovered. 

[s class]

Is step 14 described as "Remove the lock nut on the steering shaft bearing cap. I clamped it in the vise and used a chain wrench to turn the bearing cap assembly. I would have preferred to use a wrench but I did not have one big enough" the same step as you describe s-class using the modified socket and the long extension?

No.  The special socket I made was to open the crown nut on top of the piston, in order to replace the recirculating ball unit inside the piston.  This photo shows the nut on top of the piston :



In this image you refer to :



The guy still has the piston mounted on the central input screw.  The reason he has chosen to do this is because once you pull the central screw out of the piston (easy for it to slip out by accident), all the balls drop out, and it is really quite an ordeal to get them all fed back correctly.

In my photo below,  these are the top end caps with input screws, after the pistons have been removed from them. 



The nut that the guy David is wanting to  open with a chain wrench is visible at the bottom of the photo (the splined shaft lowest most in the photo is where the steering column coupling normally fits on).  The reason one might (or might not) want to open this nut is there are some/ one ? PTFE oil ring in there.  Bear in mind though that if its opened, there are bearings in there who's end clearances need to be set up very carefully again. 

Hope some of this helps. 

[DieselCop]

I had a similar problem on my 83' 240D.  I tightened up the gear box, and it help some, but not much.  I put on a new steering dampener(shock), and viola!

[agro]

I BELIVE THERE IS SOME TYPE OF SHIM ADJUSTMENT YOU CAN DO IN THE STEERING BOX  BUT I WOULD  SUGGEST THIS SHOULD BE DONE BY STEERING SPEACIALIST NOT EASY JOB.!!!! GOOD LUCK.

[koan]

Thanks for the explanation of what's going on in step 14.

I have come to believe that there is also a secondary cause of 'worn feel'.  I have found in some boxes a fair bit of end play between the central input screw and the recirculating ball unit.  I'm not sure where the wear in this area is.  It could be :

a) balls
b) central screw shaft
c) recirculating ball housing
d) combination of all three.

When I had my box rebuilt the mechanic examined the screw and explained it was the critical part, many are worn but mine was good.

Last question on the 126 steering site he says in step 10,

"....The bottom photo shows a gap between the bearing cap and the rack assembly. It needs to be tightened."

Link to picture

What gap is he talking about?

koan

[s class]

By rack assembly I would say he's talking about the piston.  I think that all he is saying is that in that photo, the input screw needs to be turned to draw the piston up agains the end cap to get it in the position required before inserting it all into the casing.