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Discussion Starter · #22 ·
Because the yoke was stuck on the transmission I had to bring it to a tranny shop to have it removed. Since it could be a while before it came back I figured I would start on the valve body. Overhauling the transmission can be divided into two segments, the valve body and the actual transmission itself. Most rebuilders will tell you the valve body is the hardest part. For me, since I've been there before, it's more like revisiting. But, it is tedious, methodical work.

With respect to 'overhauling' the valve body what you are really doing, first, is cleaning all the debris from it. I have found the 722.9 tends to get a lot of debris in the valve body and once it's cleaned out the difference is readily noticeable. Also, the solenoids tend to get clutch debris buildup in them and this affects their operation.

In addition, you must pull every single control valve and spring from the valve body and check each valve and every spring as well as the bore that the valve rides in. This is because Mercedes has known issues with respect to control valve springs breaking and also bore wear. If the springs are broken, they will still work, but not properly. So that has to be done and it's a lot more bolts and cleaning work. In addition, the o-rings on solenoids must be replaced because they too can leak causing issues. While there, you want to do an ohms test on all the solenoids to be sure they are all in spec.

Cleanliness is vital to the valve body. You cannot have any hairs, eyelashes or other debris in there. So the VB gets cleaned in gasoline several times and then goes through the ultrasonic cleaner and then gets blown dry with compressed air before reassembly. Also, every check ball and check valve get replaced because they too can wear causing hard to track down issues. Anyway, here we go....

The computer sits on top of the valve body. Mercedes calls it a conductor plate. Actually, the computer is a square device sitting in the conductor plate. Here's a pic of the conductor plate (the big black plastic piece). The actual computer (called a TCU, or transmission control unit) is the part that says Continental on it.

Computer keyboard Engineering Circuit component Composite material Laptop


This is what it looks like on it's own after it's been removed from the valve body
Blue Sleeve Dress Waist Denim


There are 8 solenoids that the computer controls to operate the transmission. They need to be cleaned as they have screens on them that get plugged up with clutch debris. The best way I've found to do that is to put them through an ultrasonic cleaner in a heated solution. It busts up the debris and cleans them inside and out. The picture is not the best but you can see what looks like smoke trails coming off the solenoids. That is dirt/oil etc being removed.

Water Architecture Flash photography Building Tints and shades


This is what the valve body looks like when the top plate (aluminum) is removed. There is a steal plate sandwiched between the two halves and it has precision holes drilled in it. You can see the plate in this pic, all the grey material? Debris from the wearing transmission;

Wood Rectangle Window Font Hardwood


This is the top half of the valve body;

Wood Font Art Engineering Metal


This is the bottom half - it contains something like 14 check balls, numerous check valves (the plastic pieces) and two rubber balls - all of which will be replaced - and all of which fell out into the gas bucket;

Font Art Rectangle Pattern Wood


This is is pic of some of the valves that were removed and checked. It looks to me like two of them are adjustable....hmmm....I wonder what that would do....

Guitar accessory Musical instrument accessory String instrument accessory Musical instrument Automotive exterior


Tomorrow the entire valve body will be reassembled with new check balls, check valves, rubber balls, and solenoid o-rings. It will then be torqued down, the conductor plate re-installed etc. It will be cleaned once more and dried before this happens. I'll also check all my valve work to ensure I didn't miss anything. It has to be 100% perfect or bad things will happen and the transmission will have to be opened up again. I don't want that. Once done it will be placed in a new garbage bag until it's needed when the rest of the transmission is done.

Speaking of which, the trans shop got the yoke off. They said it was very hard to remove so I don't feel so bad. It too went into the ultrasonic cleaner to remove rust. When it gets re-installed it's going to get a coat of grease so that never happens again. Anyway, tomorrow I'll double check my valve body work (due to the gas fumes) and get it back together and then, if there is time, start stripping down the transmission.
 

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The TCU, you who have now been there and seen it and touched it, do you think it would be possible to put a .. "dummy" in its place and pull a data cable (of some kind) and put the "real" thing on the outside?

The reason I'm asking is that there's a guy on Twitter (@RAND_ASH) that have designed and built his own TCM (hardware AND software!) for the 722.6 which works a million times better than the original :). But apparently that was .. "easy", because the TCM is under the dash.

He said he can't/won't do one for the 722.9 because it's inside, but... ?


Can the TCM be removed from that plastic holder thingie and what does it look like on the "other side" (the one that sits towards the aluminium top of the valve body)? What does the valve body part looks like, to they connect (the TCM and the valve body)?
 

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Discussion Starter · #24 ·
You can do anything, if you want to spend the hours and $$ to do it. I once created an ECU based on the Megasquirt line. I designed a circuit board, individual circuits and chose specific components for it. It cost a lot in the end. It was interesting, that's for sure, but now it sits in a box on a shelf in my garage....as I recall, there were folks using it to control transmissions. But these are very bright people.
 

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Discussion Starter · #26 ·
Valve body is done. There are 14 check balls and the kit came with 10...... Anyway, tested all of the solenoids, they are all at 4.7 to 4.9 with the Ohm Meter so no issues there. 16 new O-rings for all of them. New check valves, the two rubber balls, and I re-checked every control valve just to be sure the gas fumes didn't cause me to screw up :)

Since that is apparently 50% of the effort in rebuilding the trans, I'm half-way there.... I did manage to finally get the case off but it was getting late so I left it there for now.
White Font Art Wood Sculpture
Wood Rectangle Art Font Pattern


Font Engineering Electronic component Gas Machine


Gas Engineering Machine Auto part Titanium
 

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Discussion Starter · #28 · (Edited)
"Now you are into unknown territory for me although I will be there if you manage to smooth out the "downshift" problem. Best of luck." - thanks, we shall see...

Now that the valve body is done, bagged and sitting on a shelf it's time to get that case off.
The reason the yolk was so hard to remove was due to corrosion. Oddly enough, the rear seal was not leaking any transmission fluid but it appeared to allow some moisture in causing the corrosion. You can see some of it on the output shaft below. The ultrasonic cleaner will remove all of that. Even the tranny shop that pulled the yoke for me told me it was tough to remove.

Every video on the Internet shows people pulling them off by hand. What amazes me is that moisture got in there. When you look under the car to where the rear seal is, you would think nothing could get in and only oil could possibly get out. The fact that the rear of the output shaft was corroded tells me no oil was there. Very odd. In fact, when I pulled the case the output shaft stayed with it! Normally it falls right out in the stack shown below. I had to spray it with penetrating fluid and rap on it with a hammer to get it free from the rear bearing. So I will be replacing the rear bearing as well.

Automotive tire Tree Wood Gas Cake decorating


Some of the guts spread out on the desk

Table Gas Machine Auto part Engineering


It's very common for the 722.9 to have front pump issues. It seems that the pump bushing can weld itself to the torque converter hub and break teeth off of the oil pump gears. When that happens it damages the pump pocket in the bell housing. So, its not uncommon to have to source a pump and a bellhousing...This was one of my fears.....

As it turns out though, the pump is virtually as new, which is very good news.

Bicycle part Rim Automotive tire Auto part Composite material


So...the steel pump rides directly on the aluminum bellhousing. Not too smart in my opinion because, as mentioned, when something goes wrong it takes out the bellhousing. If they are not damaged too much you can actually machine the surface flat and install a steel pump plate for the oil pump to ride on.

However, in my case, the bellhousing is like new. Another bullet dodged!
This is a closeup of the pump pocket. Not a mark on it other than factory machine marks from 11/05
Gorgeous!

Bicycle part Rim Automotive tire Engineering Circle


Here's a shot of the whole bellhousing for reference.

Automotive tire Building Bicycle part Rim Automotive wheel system


So...You can now see that the steel pump sits right in that aluminum pocket riding on the aluminum (aluminum is a lot softer than steel). So I ordered a steel pump plate. You just put that in the pocket and now the steel pump is riding on a steel plate. This improves the design and should protect the bell housing in the future. See pic;

Font Circle Art Auto part Rim


So we dodged a few pricey bullets there. If the pump and housing were shot used ones would cost roughly $500 USD or so. A new pump is something like $800 USD alone.

Apparently it's not unheard of to need a new case as well. I suspect that's fairly rare but I don't know much about that other than some people had to replace theirs. In my, ahem, case, it was just fine!

So there's a lot of good news so far and it appears that changing the oil fairly regularly may have paid some dividends. There are many areas that are like new. However, I did find some pricey parts that should be replaced. More on that later as I need to do a bit of research first. I've also not totally stripped the components down so I have not yet seen all the possible problem areas.....
 

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Discussion Starter · #30 · (Edited)
Hi Bob!

I've been using this design;

Output device Gas Rectangle Machine Electric blue

I think they are all made from the same factory in China. I suggest minimum 10L and preferably 15L. The bigger, the better cause you can fit more stuff into them and not have to flip the parts. I use a couple of splashes of Pine Sol and the rest water. They work very well for many things. Amazon or even China direct but Alibaba will really screw you on refunds. Like hold the money for one month, so I suggest Amazon or e-bay. But I've had two of them of that design and they have been great. They don't last forever but I tend to get 3 or 4 years out of them and I use them a lot, they work great for cleaning my french press of coffee oils and grounds - among MANY other things. They are ideal for carburetors, circuit boards, you name it. Oh, and I've cleaned a few watches in them too as well as tons of motorcycle parts.

With respect to the transmission.....

I have all of it pretty well stripped down now. None of the clutches were completely gone and none of the steels were blue from burning. This surprises me because I remember at least two instances where they were smoked. One in particular when I let my cousin drive it and he smoked them so bad the car stank, and continued to stink, for 20 minutes. So I was very surprised that they actually looked quite good. Now don't get me wrong, many are thin. I did not measure the clutch stack freeplay during disassembly but I did check it by hand and it seemed like a lot. I am certain some of the stacks were way out of spec. Some of the disks are very thin.

Let's quickly revisit why I wanted to rebuild it. One, the 3-2 coast-down clunk was driving me nuts. Two, I knew the clutches had been burned (abused) because I did not do the conductor plate as quickly as I should have. Three, I looked at the transmission adaptation logs in DAS and found that several were not able to adapt anymore because they were at their limit, or there was something wrong. This made me think that perhaps that is where the 3-2 coast down clunk is coming from - clutches that could not longer adapt (at their limit). Four, it has a bit of whine in the lower gears although that didn't bug me too much. Oh. and the usual symptoms they exhibit when the trans needs a service (that had to be done regardless).

Anyway, as I was stripping it down I did find some areas of concern, notably wear on the splines that the clutches ride on. Here's an example;

Automotive tire Gas Engineering Machine Coil spring


Now, some wear is normal. But there are areas on that part (rear planet) where it's sketchy. The grooving is such that I can see the clutches having problems moving over those ridges. I was advised by an experienced Mercedes mechanic that, if it was his car, he'd replace it. I asked him if he meant the part, or the car!! That part, btw, is $375 USD....

But where it gets a little complicated is that the 722.9 has had many updates over the years and they are retroactive. That is to say, that part has been updated about 4 times by Mercedes. This means you can no longer by that exact same part because it's been....updated. Which is fine, but...what that also means is that the part that it mates up to has to be updated....So...in order to buy that one part, I actually have to buy 2 others so that they will all match up. The other 2 parts have also been updated 3 or 4 times over the years....As you can probably guess, it's a recipe for confusion.

Because my car is 2006 (actually 11th of 2005 or so) it means that most of the parts in the tranny have been updated several times. Now you don't have to update them all, but in this area of the trans, in order to get that one part, you must buy 3 altogether. The good news is that 2 of the 3 parts have considerable wear on them. The bad news is that the $375 USD for that one part turns into $900 USD for the three parts plus duty/fees. Also the exchange rate. $900 USD = $1,200 CAD plus taxes....

The original budget was $600 CAD for trans service parts (filter, updated pan, oil etc) plus $1,000 CAD for overhaul kit (clutches, pistons, steels, gaskets) and then ancillaries such as new aluminum bolts. Call it $1,800 CAD. Now it looks like it will grow to $3,200 CAD / $2,400 USD

So it started like this. I had the trans service parts all here and sitting on the shelf. It then occurred to me that I'm really just treating the symptom, because I knew the clutches would be worn. $600 to treat the symptom, why not just buck up for $1,000 more and be done with it? Besides, the $600 would be wasted anyway because sooner or later the trans would need to be done and then you have to put new oil and filter in it anway. Makes sense right?

Anyway, I spent the weekend humming and hawing about just how much I want to spend on the transmission. Especially since I have yet to see anything that would suggest to me is the root cause of the 3-2 clunk, other than the obvious clutch wear. But the trans also had a bit of a whine coasting in the lower gears. I'm thinking that rear planet could well be the cause of that. Not due to the splines, but probably due to wear on the bushings in the planets.

The rest of the transmission looks very much as new. In fact, here's a picture of the parts bucket with parts that passed inspection;

Automotive tire Gear Automotive lighting Rim Household hardware


So the real wear seems to be limited to that one area in the transmission, the rear planet.

As you can probably guess, the question in my mind is how far do I want to go? On the other hand, the rear planet carrier has 4 planet gears that will have bushing wear as well. So I'm not just getting virgin splines for the clutches to ride on, I'm also getting 4 new planets with proper end-play. Also, the second part will have virgin splines and they are also worn on the existing one. Plus, these are updated parts. What problems they solve are unknown to me, but perhaps they flow more oil to help keep the clutches from grooving the splines? No one really knows. Better yet would be if they flowed more oil to the rear seal in the transmission because there was rust (!!) present there when you would think that seal would be holding oil in! They may well do that.

I'm probably being a cheap bastard but the fact is, when I look at all the brand new parts on the shelf already, I start feeling guilty! On top of that, I'm negotiating with China on an Xtrons head unit. More guilt! (Also, much more work!). And...it still needs 4 new tires... and an alignment....

But it takes quite a bit of effort just lining up the correct, updated parts, including their dependencies. Bear in mind, in Canada they want $1,300 for the part that is $375 in the US. So I have to shop in the US which adds about two weeks to every order. So you need to group your orders because it's going to be ~14 days before the parts show up. Which means the car's stuck on the hoist and tranny parts all over the place. Plus, 14 days later none of this is fresh in your mind so when the parts do show up, you have to get back into tranny mode. Mind you, I took that all into account ahead of time, and, to be honest, I had a feeling that I would have to replace some of the hard parts. I kept seeing a picture of the planet gears in my mind long before I pulled the trans.

So the current thinking is this, order the new parts tomorrow, they will check on availability for me (hopefully NOT Germany) and then, in the interim, I will do the front and rear suspension and possibly just buy the damn stereo and get it all done and over with in one giant shot. And then that's the end of the car, as far as work goes, for hopefully several years!

Here's a pic of the piece that has to be replaced when you replace the rear planet carrier. It's actually two pieces, the shaft and the gear. The shaft has no wear, but it's been updated...but you can see more clutch marks on the gear.

Automotive tire Gas Nickel Wood Engineering


I should probably just be happy, because all these parts are in the same area and 2 of the 3 are worn. I'm also reasonably sure that whine is coming from the rear planets and the bushings for each of the 4 planets do wear out. So I'm kind of blanketing a lot of potential issues with one shot, so to speak.

One thing I am sure of. Replacing those parts will get the trans to roughly 98% of brand new. There really is very little wear anywhere else. At the end of the day, up here, Mercedes quoted me $15,000 for a reman transmission. Even if I could find a good tranny shop, I guarantee you they would want $6,000 and probably $7,000 for the job. So it's not wrong to say I'm doing it for half price of a rebuild from a tranny shop, and the other side is...it will be done right. But, when done, I would think it's got to be good for at least 200,000 KM's. Its at 175,000 now and with the updated tranny pan/filter,conductor plate, and regular servicing I can't help but think it's a one and done. I should have updated that tranny pan and filter long ago and got on that 3-2 coast down clunk but I asked a lot of people and had no response. I've still had no response on that, other than some have found the solenoid o-rings addressed it, which makes sense.

The valve body is spotless. The solenoids all spec out perfect, and are spotless, and there are new O-rings on every one of them. With new clutches, set to the correct gap, it should be able to self-adapt again. That will show up right away because no matter how I drive it, I cannot get DAS to manually adapt the 1-2 shift, which is apparently the same as the 3-2 downshift. So when you adapt 1-2 up, it also adapts 3-2 down. But it will NOT adapt it and the logs indicate its at the limit of adaptation.

Hopefully the rebuild will address the 3-2 issue because I just can't see any mechanical reason for it at that point. If it still does it after this, it has to be software. That is the only thing left. After this, the trans itself will be 100% on every front.

So that's the news, and that's the reason for the delay in posting about it. I needed to really think it through because I was tempted to just put in new clutches, steels, pistons and set the gap on all the clutches and see what happens. But then I saw a video from a great trans rebuilder, with a lot of experience, and he was showing the same clutch grooving on the splines (on a domestic trans) and he went into detail about what the clutches do when they hit those grooves. They move around. Some grooving is normal wear, but on that aluminum carrier there are some spots that are pretty darn rough.

Anyway, clearly the tranny is not the only thing that has a bit of whine to it ! :)
 

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As for the splines being worn, I don't know if you can do this on an automatic gearbox, but we shimmed the axles and gears on our old Volvo (manual) gearboxes to get the right splines play.

These where gearboxes that had gone A LOT further than 200k km!! :D Think four, five times that :D. Where we could (if it was too much for shims), we Tig welded [the splines] and simply filed it down until if fit.

Now, granted that's on a gearbox that's .. well, there's no comparison with a 722.9 obviously, but a good mechanical workshop should be able to do the job just fine. They have computer guided machines now :D :D.
 

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Discussion Starter · #33 · (Edited)
Not a lot I can do until my trans gel arrives on Thursday so I decided to throw my output shaft in the ultrasonic cleaner. So I thought I would mention how I clean the parts;

1) A good wash in gasoline primarily to get rid of the oil.
2) Blow dry with compressed air
3) Ultrasonic cleaner
4) Wash in Brake Kleen
5) Blow dry with compressed air.

If you do it that way the washing fluid in the ultrasonic cleaner doesn't have to be changed often as you're feeding it clean parts to begin with.

The reason I mentioned getting the largest cleaner you can is so that you avoid this;

Automotive design Engineering Gas Machine Automotive tire


...a part being half-cleaned. There's more to it than that. You can see rust starting to form on the shaft already. When the steel is spotless it rusts very fast. When the entire part is submerged it won't until you remove it. But...because the solution is heated (in this case 41c) when you pull the entire part it's...41c...so it dries itself very quickly. With half of the shaft out of the solution it's getting hit with steam from the bath. So...there's more to buying a large unit than you might think. Not only that, but if you have a larger unit you can keep the lid on it which of course gets the solution much hotter. I normally run the bath at around 65 to 70c...

Between the transmission and the suspension work I'm fighting for bench space :(

Computer Electrical wiring Gas Machine Electronic device


Here's a video of the ultrasonic cleaner getting into ALL areas of the rear shaft including between the sun gears etc. You can watch the smoke come out from between the planet gears. This cleans EVERYTHING and it also removes rust which you will see shortly...

Unfortunately, the site won't allow me to embed the YouTube video so just click the link below to see the dirt and debris contrails. Bear in mind, this is after being thoroughly cleaned in gasoline and brushed. Nothing can clean the inaccessible areas like an ultrasonic cleaner. For carburetor work, they are unreal. Shame the site won't let me embed the video...

722.9 in Ultrasonic Cleaner
 

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Discussion Starter · #35 · (Edited)
Nice video
Yeah, it's a little nicer to see it in action than to explain it :)
Speaking of which, this is what the yoke looked like before being cleaned.

Window Wood Gas Machine Engineering


This is the after ultrasonic cleaning

Wood Bicycle part Rim Bicycle drivetrain part Tool


My assembly lube arrived today so I was able to assemble the B3 Clutch Assembly!
I installed a new piston as well as the updated retaining ring. The stack then got put back together with new frictions and I could measure the gap for the stack. Turns out, I'll need to order the thinnest retaining ring. The existing one is much too thick and there is not enough gap. I guess my disks are a little thicker than Mercedes disks. Pick to follow, but at least I've almost got something done other than the valve body!

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Very good report Marvin. Noted your info on the Ultrasonic Cleaner. I am still unclear on the reasons for my downshift problem. Mine is not a "clunk" but a smooth/ severe EXTRA brake effect, somewhat harsh when braking to a stop at the lights. It occurs in S and C and not a worry for mechanical reasons but just "nose on steering wheel" when slowing down at +/- 5 kph. Like you, I have been avidly checking out all info I could find but so far, I don't think even MB knows much about cause. Following your adventure with great interest but must admit costs are getting close to my limits but the alternative seems even more unwelcome. Best of luck..........
 

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Discussion Starter · #37 ·
Believe me, I hear you on the costs. And there's another side to it as well. I just ordered up the thinner retaining ring and a spring plate and was told they are shipping out of Germany - 3 to 4 weeks as a possible ETA.....These cars are not easy. And then there's the German/English issue that you run into all the time. And then you have to have EPC/WIS installed in order to do your job....and DAS/XENTRY....and a plethora of special tools. And an alignment shop that has to have special equipment. And of course the special transmission fluid, and even the special engine oil....

I'll quit whining now before I lose all ambition ! :)

I look at it this way, I like the car, it's a unique car, and the cost of replacing it is much, much, much higher than the roughly $5k I budgeted for it on the repair/maintenance front. At least, that's what I tell myself late at night :) But it's not an easy car to own. Not in the least. Especially when you use it as a daily driver. When you put miles on them, boy do they cost. And then there's geography considerations. In europe clearly they are a common item due to close proximity to Germany. So parts supply and shops are probably very well acquainted with them. This is not the case in Canada. Compared to a GM, Ford or Chrysler, they are fairly rare.

Very little of my parts orders, over the time I've had the car, came from Canada. Estonia and the USA are where most of my shopping is done, in that order. If I need aftermarket or OE it's Estonia. If I need the dealer, it's the USA. It is NOT a practical car to own.

The people up here that have them are relatively high on the income scale. This means it is typically a second or third car and that means they are used on sunny days and special occasions. That means low mileage and, consequently, low operating costs. I'm going against the grain on that front too, and it costs.

But, I'm in it now. And on the other hand, it's a privilege to work on that transmission. Not enough has been said about that. It's a remarkable piece of engineering and it's so compact. It's actually a very tiny transmission with some huge parts inside. If I can get the bugs out of it, and I've gotten lots out already, I'm hoping for a one & done. At the end of the job the only thing left is the engine, and so far it's great, so maybe I will win the war after all :)
 

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Discussion Starter · #38 ·
Some more progress.....

The pump bushing clearance was less than .002 which is fantastic. I believe the spec is actually 5 thou or less. This would account for the bushing which appears new after 175,000 km's. So this saves me from re-bushing the pump and having it honed to spec for the converter shaft :) As such, I put a new seal in it and called it done. No sense messing with perfection....

I then installed the new pump plate and the pump with a new seal and a new O-ring, an new metal gasket and the stator with 2 new torlon rings. I torqued the stator down and then installed a new piston, put the spring plate in, and then the second updated snap ring, and started filling it up with clutches and the pressure plate. I removed 8 clutches from the B1 clutch assembly and put 8 new ones in.....

I then measured the clearance and looked in the book. This is where it got interesting....the book lists clearance specs for a clutch stack with up to 5 (!!) disks. Yet mine has 8....No problem, I said, I'll just go through WIS and get the spec direct from Mercedes....Surprise! Mercedes also lists up to 5 clutches....But I have 8.....

Anyway, time to talk to a Mercedes tech in Germany. Otherwise I'll have to extrapolate what the stack clearance should be...

Anyway, here's a shot of the stator/B1 pump assembly with the clutch stack all done up (other than the clearance...) you can see the nice new blue piston in the bottom and the thrust washer installed etc.

Light Automotive tire Rim Bicycle part Machine
 

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The people up here that have them are relatively high on the income scale. This means it is typically a second or third car and that means they are used on sunny days and special occasions. That means low mileage and, consequently, low operating costs. I'm going against the grain on that front too, and it costs.
Now retired and mine indeed only gets used on sunny days. 🌞
But....first 2 R171's I had were used as a daily driver to work. Meaning 200 km round trip every day. All year round,also during winter with snow and salted roads. They never let me down. Only regular maintenance,nothing extra ordinary.
No guarantee ofcourse,but you might get a pleasant surprise on that going against the grain thing. :D
 

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Mercedes also lists up to 5 clutches....But I have 8.....
This stuff is way over my head but doesn't WIS doc GF27.51-P-5200W,the one they refer to in the doc describing the clearance adjustment of the multidisk brakes lists B1 consisting of 4 internally toothed plates and 4 externally toothed plates? Together 8?
Or am I reading this completely wrong? Like I said,way out of my league and sorry if I may cause any confusion.Just curious and trying to learn.....;)
 
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