Transmission Service DIY - Mercedes-Benz Forum
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#1 (permalink) Old 01-22-2012, 06:13 AM
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Transmission Service DIY

This is intended to summarize forum lessons learned for periodic Transmission Service: Oil, filter, and adapter plug change outs. I have an S430, ML320 and E420 which all share the 722.6 five speed transmission; and have performed this service a total four times. (Time spent on the last change was approximately 2.5 hours, taking my time, from car up to car down.) Attached are what I consider to be the best links on how to perform this service. Most of the lessons learned are from the E class W210 forum, which uses the 722.6 transmission, and contains a wealth of information at: http://www.benzworld.org/forums/w210...nsmission.html

This thread is not intended as a comprehensive diagnostic or repair manual. Information in this write up is intended to provide a summary overview of Transmission service of fluid, filter and adapter plug replacement. Lessons learned are incorporated from myself, and other forum members with the links provided. I have also included technical details from different sources. If you use this write-up, you are assuming all liability for injuries or damages. Just to be clear, if you stub your toe, blow up your car, electrocute yourself/wife/child/dog/mother-in law, if your cat throws up, or if anything less/more horrific than described above happens after reading this missive; you are responsible for the outcome, not me.

You get to choose the variables for transmission service such as: Brand of ATF to use, how to and much ATF to flush, brand of adapter plug, contingency parts and tools to have on hand. It is your car, you have to make and live with the choices.

The 722.6xx electronic transmission came to the USA in 1996. It is used in a wide number of MB vehicles, and Chrysler vehicles such as the Crossfire. (Instead of 722.6, Chrysler designates this transmission as ‘NAG’). Not all 722.6xx transmissions are alike. Different gear ratios and torques are achieved through alternative ratio planetary gears and other internal components. The ‘xx’ designator is what differentiates between these transmission variants. This is MB first computer controlled transmission, and is a 5 speed. If a replacement transmission or Transmission Control Unit with a mismatch between original variants is utilized, the TCU will detect this, provide error codes, and this will result in poor performance. Full transmission variant types are stamped on the left side of the casing.

Links
There are several transmission variants for the model years of the S, E and ML classes. For detailed information, see http://www.scribd.com/doc/37436253/722-6 (be patient its a long download for a large technical file containing pictorials that is worthwhile, but has a $9 fee)

The simplest and best instructions for filter and fluid change out are by GAMG: http://www.benzworld.org/forums/w210...ion-fluid.html

A good review for adapter plug changeout from the W210 forum with good photos. My only addition is that it is less of a mess if it is performed with first draining the fluid in the pan so it does not run out of the front connector housing. http://www.benzworld.org/forums/w210...sion-plug.html

One technique for flushing transmission fluid is the Yummling Flush: http://www.benzworld.org/forums/w210...ion-fluid.html. The MB WIS indicates to drain the tranny sump, (and torque converter prior to manufacture of 2000) remove the cover and filter, then inject the clean fluid through the cooler intake, as the dirty fluid is pushed out of the governor.

I now prefer the repeat drain or suction method. My personal choice is to use a fluid extractor system, and do this in stages. It is a less efficient method for ATF exchange since there is mixing, but it is one less connection to break during the process. Another positive is that taking multiple steps also allows adjustments for getting the fluid level perfectly between the marks on the dipstick.

The original MB ATF part # is 001 989 21 0310. It is the most expensive option, and can be purchased from Autohause. I have been using this on three cars for over a combined post service 100,000 miles without problem. I recognize that the MB brand is what I am paying for, and this is likely just rebranded Fuchs ATF.

Other Materials

The MB trans dipstick is part # 140 589 15 21 00.
Trans magnet 2202710098
Lock clip for filler cap is A1409910055 (I don’t bother with these anymore)
Drain gasket is A1402710060
Trans filter 1402770095
Pan gasket 1402710080
Adapter plug (Available at any Chrysle dealership for NAG transmissions) Checked the EPC with the original part number that was on the existing connector plug 203 540 00 53 and it has been superceded by 203 540 02 53. DON'T BUY URO BRAND UNLESS YOU HAVE MB O-RINGS.

Complete this the day before starting:
Warm the car up by driving 20 miles and checked with the dip stick with car running.

The oil level should be between the 80 degree marks. (This way when you drain fluid, you can verify that the ATF was properly topped off before you begin the service. A properly filled transmission will show 3.5 Liters total with the pan drain and drop.)

CAUTIONS

Measure carefully, follow directions.

Keep anything coming in contact with the transmission interior surgically clean. The valve body contains ball bearing sized seats that can easily be clogged with debris.

TAKE METICULOUS CARE TO NOT OVER OR UNDER-FILL THE TRANSMISSION. APPARENTLY, THESE BOXES ARE VERY SENSITIVE TO ANY DEGREE OF CONTAMINATION OR IMBALANCED FLUID LEVELS. IF YOU OVERFILL, YOU NEED TO SIPHON OUT EXCESS.

Start with a cool engine don't have the fluid hot. (Having a hot engine also makes for it dangerous to work around the catalytic converters)

Keep you car supported safely while working underneath to avoid being crushed.

TIP - best approach for connector replacement is from the front of the car. Tried to crawl under from the side during my E420 pan drop, filter replacement and connector changeout and could not get a good view. Crawled in from the front on the S430 for connector changeout, and it was easy.
Attached Files
File Type: pdf 722.6 ATF flush.pdf (271.0 KB, 2761 views)

Last edited by Skylaw; 08-19-2013 at 05:44 AM. Reason: Repaired broken links
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#2 (permalink) Old 01-22-2012, 07:17 AM
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Thanks for sharing your experience, atmsmshr - I'll add this to the Encyclopedia in the upcoming revision.

Warren

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#3 (permalink) Old 01-22-2012, 09:03 AM
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How often should the fluid be changed?

Rodney 2006 S500 4matic
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#4 (permalink) Old 01-22-2012, 12:31 PM
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When I drained mine from the plug, it took 3qts. When I drained it from plug, then removed pan and filter I think it was 4qts-and change.

Chris

2000 S430 - 18" AMG Wheels / Hankook Tires, Bi-Xenon 03+ Headlights, 03+ OEM Taillights, 03 Comand MOPF, Speed Signal Converter, MB Bluetooth V60 Puck, Wood Trim/Leather Steering Wheel, Universal PSE, JL 10" Wv3, Arc Audio Amp, LC2i Line Converter, Custom Exhaust, Custom Armrest, Custom Parktronic System, Carbon Tint 18 Rear, 30 Sides.

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#5 (permalink) Old 01-22-2012, 01:32 PM
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Quote:
Originally Posted by Mera View Post
How often should the fluid be changed?
Under my owners manual 'Practical Hints', page 343 it states: "The transmission has a permanent fill of automatic transmission fluid. Regular automatic transmission fluid level checks and changes are not required. For this reason the dipstick is omitted. If you notice fluid leaks or gear shifting malfunctions, have your [dealership] check the transmission fluid level."

That being said, most long term MB owners want their transmission serviced, and many on the forum think the 'transmission sealed for life' concept is not in the long term interest of the mechanism.

I asked my local MB dealership Service Advisor what they recommend to help prolong the life of the 722.6 transmission, and they stated a fluid and filter exchange every 40,000 miles would be beneficial, coupled with an adapter replacement. That being said, MB dealer ships use the ATF designed for the 722.9 transmission when servicing the older 722.6 transmissions. Not my preference, but it is allowed by current technical data. http://bevo.mercedes-benz.com/bevoli...&language_id=1

The 40,000 miles interval along with using the original spec ATF is the approach I take. However, everyone makes their own judgement and gets to live with the results.

Here is the English from German translation of the service bulleting 'clarifying' the sealed for life position described in our owner's manual.

New M-B bulletin, re: 722.6 & 722.9

In march of 2003, M-B released a bulletin, advising a one-time-only transmission fluid change @ 40 k miles.
This is to remove any particles that may have accumulated during break-in.
At the same time it is also advised to change the fluid on the 4-matic transfer case
****************************************

Circular PW NR. 44/05 NFZ NR. 20/05 24.03.2005 to all Mercedes
Benz partners

Introduction of the transmission oil changing with automatic
transmissions 722,6 and 722,9, as well as with the transfer case of
the 4MATIC-Typen 203/211/220 uniquely with 60.000 km.

Ladies and Gentlemen

A substantial criterion for the customer satisfaction with
automatic transmissions is the switching quality. This not only in the
newer status of the transmission, but constantly over the entire
Lifecycle.

After the introduction of the optimized lamella package in the
transducer bypass clutch (increase of the number of grooves on 72 to
02/2004) to the long-term stabilization of the switching quality, as
well as, the oil change represents a further step to the conversion of
the NAG1 to the oil used with the NAG2 for switching quality
optimization, in order to hold the switching quality also with high
run performances on a high level. In the oil stored particle is
removed by the unique oil change, whose entry takes place to a large
extent into the first 40'000 km and it can have impairments of the
comfort of the switching quality why a unique (and not in turn) oil
change was determined.

For this the again developed transmission oil ATF3353 (AO019894503)
makes an additional contribution that we fill in automatic
transmission 722,9 since serienanlauf, with these automatic
transmissions from house. In the transfer case of the 4MATIC-Typen
203/211/220 the oil 001,989 2303 is used, in order to likewise hold
the comfort self-shadows of the 4MATIC-Systems high level with the
change.

Deviating of it a transmission oil changing with the oil FOX ATF 28
(AOO19894603), developed particularly for it, is to be executed
starting from introduction with the transmission 722,8 (Autotronic,
type 169) all 60,000 km.

For vehicles with ASSYST the service position was already taken up to
the maintenance scopes. We will extend the service pages by the note
starting from FIN XXXXXXXXX, are evident starting from WIS update
03,05 the corrected service pages. For vehicles with ASSYST plus is
caused the service position to the service page automatically by the
maintenance computer. The modification of the data records necessary
for it is only possible starting from data record release 09,2005.

Last edited by atmsmshr; 01-22-2012 at 02:43 PM.
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#6 (permalink) Old 01-22-2012, 01:57 PM
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Fluid level

Quote:
Originally Posted by cmpcpro View Post
When I drained mine from the plug, it took 3qts. When I drained it from plug, then removed pan and filter I think it was 4qts-and change.
Chris - That is comparable to my last fluid quantity recovered, mine was 3.5 Liters. It is a shame that the 2000 MY and on do not have a Torque Converter drain, I can drain a lot more on my older cars.

Total fluid Transmission (proper fill) capacity is 9.1 liters, from Technical Data of the owners manual.

You should get a total of 3.5L drained and poured from the pan from a properly filled transmission (when it is cold). Some folks getting 5L are either draining it hot (a burn hazard and not required with a pan drop and filter change) and/or have an overfilled transmission.

After running for a few days after a pan drop, you can try a topside partial fluid exchange. A 1/4 inch diameter drain hose at least 32 3/4 inches long can be used with a fluid evacuator to get 2 Liters (cold) of AFT out through the dipstick tube. The 1/4 dia gets it past the fill tube restriction, the suction tube length bottoms out on the pan. (See photo, white extractor tube hanging down) After doing this a few times, the fluid will be 95% exchanged, without having to do multiple pan drains or breaking the banjo fitting.
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Last edited by atmsmshr; 01-24-2012 at 02:41 PM.
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#7 (permalink) Old 01-22-2012, 02:34 PM
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Measuring ATF level

The transmission does NOT come equipped with a dip stick for checking fluid level. The filler tube has a locking plug in it from the factory. (A black locking tab usually means factory original, a missing or red tab means that someone not authorized has previously pried off the original)

When fluid level needs to be checked use a screw driver to pry the lock from the plug and remove the plug by pushing down the remaining piece with a thin blade screw driver. (The remaining piece will fall into the engine bay, not the transmission.) I no longer bother with reinstalling the lock tab. The plug top has stayed on all 3 of my vehicles and none have rattled off. The lock tab was just a tamper device for warrenty purposes, coupled with no transmission dipstick and the 'sealed for life' concept. (IMHO).

While in Park at idle, use the dipstick tool to check fluid level by inserting the dip stick into the filler tube until fully seated, wait 3 seconds, then remove the dip stick and check the fluid level indication on the dip stick.

There are two ranges, one cold (25 deg C) and one hot (80 deg C). Proper level in the cold range means that the fluid is at the bottom of the valve body and the pump is not sucking air. Proper level in the hot range means that the ATF is not challenging the float in the conductor plate (could cause frothing) and that the Adapter Plug is not submerged in oil. (Could cause wicking fluid inside conductor insulation up to the Transmission Module in the fuse box).

The tip of the dipstick shows these fluid ranges, which are only valid with the engine running and the transmission in park. The tip of the dipstick also has small diamond shaped 'wings' that come up against the tube stop. (See photo at 2.75 inches) The stop with the diamond wings allows the dipstick to hang down in the pan fluid (see photo), and not come in contact with the pan bottom.

NOTE - Some have advocated making their own dipstick - IMHO there is a high probability of error to accurately measure MB ATF level with the stop feature missing. Spend $30 to do it right and buy the tool. (Search for "722.6 dipstick" on ebay)

With the diamond stop feaure, the dipstick is a universal length that can be used with varing tube lengths. This means that the tool will have excess length hanging out when fully inserted. (Unlike those other brands were the stop feature is at the top of the tube.)

It is difficult to get a consistent reading AFTER filling by using the dipstick tube. For this reason, it is good to know the level of the ATF before the service, and to measure the fluid drained to help with proper refill.
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Last edited by atmsmshr; 01-28-2012 at 11:44 AM.
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#8 (permalink) Old 01-27-2012, 06:17 AM
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Car Jacking

Since a transmission service means you will be spending quality time under the car, here is one process for ease of jacking up the car, and to ensure your safety.

In order to maximize the ‘throw’ of the hydraulic jack arm:
1) Start the car and engage the Airmatic 'Raise' feature.
2) Place car on a level concrete surface such as a garage.
3) With an assistant, positioned 2 wooden chocks in front of the front tires, and roll the car up to sit upon these blocks.

Steps 1) and 3) together provide several inches of height for better clearance of the hydraulic jack handle.

4) Transmission in Park, shut off the engine, remove key and engage the Parking Brake.
5) Chock the back wheels using four 2x4s.
6) Position the hydraulic jack under the center lifting point in the engine compartment. (use a wooden block between the jack and lift point to gain additional clearance if needed)
7) Raise the car to the point to install the jack stands under the rubber pad side mounts behind each front wheel well.
8) Slowly lowered the car onto the jack stands, and then reclosed the hydraulic bleed screw with the wooden chock still in contact with the rubber center jacking point. (just for added safety)

The photo below shows the extra clearance for the hydraulic pump handle after doing steps 1 and 3. Without this extra clearance, you cannot use the pump handle.
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#9 (permalink) Old 01-27-2012, 06:48 AM
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Fluid Condition and Pan contents

What you find when you drain the oil and drop the pan is an indicator of the health of your transmission. There used to be a link available called ‘The Color of Money’ by a Transmission shop specializing in 722.6 transmissions. However, that link is no longer available. Some of the highlights are shown below, including some personal experience.

The use of a lint free white rag to wipe the dipstick on automatic transmissions is advised so that the color of the fluid can be checked. Dark brown or black ATF can be an indicator of a transmission problem, vehicle abuse, or fluid that has far exceeded its useful life. Overused ATF often has reduced lubrication properties and abrasive friction materials (from clutches and brake bands) suspended in it; failure to replace such fluid will accelerate transmission wear and could eventually ruin an otherwise healthy transmission. However color alone is not a completely reliable indication of the service life of an ATF as most ATF products will darken with use.

The Color of Money:

We have been conditioned to judge the quality of the transmission fluid based solely on it's color and smell. We have no way of judging the frictional quality. The rules have changed. The bright red color that we are all used to seeing may not be what you see when you look at the ATF in a 722.6. The reasons that the oil looks differently are as follows:

1) The oil may appear dark red due to the graphite material that the friction discs contain. This does not change the characteristics of the oil. Do not change the oil or transmission if the oil appears dark red or even if it has a yellowish tint to it. The color will change with time and temperature.

2) If a copper color is seen in the oil pan the bushings of the front or rear planetary gear set may be in the process of wearing out. Inspect the bushings and if they are defective replace the complete transmission. If they are not defective, then the transmission is repairable.

3) If a silver color is present in the oil it may be a clutch and steels moving up and down on the hub as they are being applied. This is normal! The particles should not cause problems as they will be trapped in the filter. The fluid could be drained, including the torque converter (if so equipped), and the lines flushed and the valve body should be disassembled and cleaned. Of course, replace the filter. This usually takes care of the problem. If you take the time to inspect and clean each slide valve for ease of movement and base position you will have a better valve body than a new one from spare parts. In more severe cases where the particles are large, then something is in the process of self destruction and the transmission should be either replaced or repaired. Don't forget to check the electrical solenoid valves. Shine a light through the top of it and see if it "leaks". If you drop the transmission oil pan and you find yourself feeling like a miner panning for silver, or knee deep in a graphite colored mud, then it's time for a new transmission. The new pans are painted black on the inside. The metal particles show up better against a black background as opposed to the previous unpainted silver pan. You must get used to seeing some metal in the bottom of the pan, with this 722.6 transmission this is normal.

4) Smell the oil. You know by now what burnt oil smells like. If it looks burnt, and it smells burnt, then its burnt. This means that your service interval needs to be more frequent to match your driving conditions.

Finally, some thoughts on filters. Due to the geometry of the pan drain plug, it is impossible to get all of the ATF out of the pan just through the plug. This drain is unlike the engine oil drain, and sits in a raised boss which will prevent graphite sludge and large particulate from being removed. Therefore, the pan must be dropped. The photo below from an S430 shows graphite wear particles trapped in the bottom of pan. This was more than what I've seen before, probably because I went close to 50,000 miles since the last service. The filter element is coarse enough to allow passage of graphite, but to stop metal particulate shown in the photo below from an ML320’s dissected filter housing. (Unknown mileage since last service since I bought it used) The coarseness of the filter is another reason to use lint free cloths and be surgically clean when servicing your transmission, because lint may travel past the filter to the seats of the valve bodies and solenoid valves.
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#10 (permalink) Old 02-05-2012, 06:44 AM
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Transmission Adapter Plug

Just so no one tries fixing a leaking transmission electrical plug with an inferior product........

After reading posts of the URO transmission electrical plug not being up to par, I got a MB plug from the Chrysler dealership to compare with the URO plug previously ordered from AutohausAZ. (A MB part in a MOPAR box, not something one would expect to see - ask for a Chrsyler Crossfire NAG-1 transmission adapter plug for $12)

A quick visual did not show any differences. A dimensional comparison of the plug bodies with calipers showed they were the same.

However, a dimensional check of the smaller O ring showed that the URO was thinner than the MB plug when installed on the plug. The upper O ring was also thinner. It is obvious on the photo shown below. Both plug adapters are new.

Once the O-rings were rolled off the plug bodies, the size differences became clear.

The smaller of the two O ring's is critical to keep ATF out of the conductor plate shroud connection (sealing location "1" - on photo)and the larger O ring keeps ATF from leaking to the outside of the transmission (sealing location "2" - on photo). A less tight fit of the URO plug may increase the chances of ATF leaking into the connector and wicking up inside the wiring insulation to the Transmission Control Module.

This past 6 months, I used a new MB connector plug on our ML and and suprisingly reused the URO body on the S class. For both, it was difficult to get the MB center 7mm bolt to engage than compared to the last time I changed a plug on our E420 – with a URO. Suspect that the smaller O-rings on the URO make for easier seating, but inferior sealing. Additionally, a closer inspection of the the center bolts between the two adapter plugs showed that the URO has an extra length of thread than the MB brand. This means that the center bolt will catch easier on the conductor plate cup (photo below, red circle.) If you cannot get the MB brand adapter in place, you may want to swap the MB O-Rings onto a URO plug body to take advantage of the extra thread on the bolt. This is what I had to do on the S, even after trying the tricks of of lubricating the O-rings with ATF and stuffing some paper towel inside the 7mm socket to get better seating force.

One more tip when you change the adapter plug - ensure that both of the O-rings come out with the old adapter. It will be nearly impossible to seat a new adapter with an old O-ring remaining in place.
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