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Post Info TOPIC: Mercedes-Benz Transmission Part Numbers - Useage Guide W126 420 and 560 Sedans


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Mercedes-Benz Transmission Part Numbers - Useage Guide W126 420 and 560 Sedans


I have been seeing more and more people installing the wrong transmissions in their Mercedes. Many people are under the false impression that all transmissions for the V8 86-91 Mercedes are the same. This is absolutely wrong and should you install the wrong year/part number you could be in for a host of problems from hesitations to improper shifting.

There are many different part numbers located on a Mercedes Benz transmission. One of them is stamped on the case with raised numerals, another one is on a tag, but the one you want to pay close attention to is usually stamped into the lower front passengers side just under the dip stick, often covered up by the wire rail for the O2 sensor. This part number is the one you want to use when trying to determine the application.

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MERCEDES-BENZ TRANSMISSION PART NUMBER GUIDE (USA)

1986-1988 Mercedes-Benz 420 SEL -  722.324
1986-1988 Mercedes-Benz 560 SEL -  722.323

1989-1991 Mercedes-Benz 420 SEL -  722.355
1989-1991 Mercedes-Benz 560 SEL -  722.350

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Use of the proper transmission can make all the difference in the world. Even though your transmission may only be one number off, that can make a huge difference, most of the times with the electronics. When you mate an improper transmission to a Mercedes, often times the electronics will not function proper and can cause all sorts of problems. Using the guide above to select a used transmission or identify yours can save you lots of time and money.

While it is true that many of the internal parts of these transmission are the same, it would take a great deal of time, skill and labor to make them work proper, and even then the case will NOT reflect the changes, leaving someone else to get really jammed up.

Best to stick with the part numbers.


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Recently I have had a problem with my alleged "Newer factory rebuilt" Mercedes-Benz 560 transmission.

Awhile ago I replaced the entire engine and transmission in a black 1990 560 SEL that I had purchased. The original engine had a valve seat that came loose causing the dreaded timing chain failure. It's the first time I ever seen the valve seat fall out of an M117 head. Anyway, at the time I purchased the 1990 560 the previous owner informed me that a newer Mercedes-Benz factory remanufactured transmission had been installed. Knowing that I saved the transmission for later use in my 1991 560 SEL daily driver should my trans ever go bad.

Well a few years later the reverse finally went out in my daily driver 1991 560 SEL and I elected to install the factory reman unit removed from the above mentioned 1990. I installed the transmission and found an odd flare up to occor on the 1-2 upshift. I made ajustments to rectify the problem, but then near Christmas I took a long trip on the expressway only to arrive at my destination with the transmission growling similar to how a power steering pump sounds when it's low on fluid. About 10 minutes later I noticed that it was leaking slightly as well. On the way home I was good and pissed and pulled a whole shot pulling hard up until speeds slightly over the posted limits wink, it was at that time that I noticed the vehicle started smoking like a tire factory on fire. I pulled over to inspect what happened and apparently the leak had gotten much worse. I immediately got some Lucas trans conditioner so I could make it home without using one of my AAA tows.

The thing I love about Mercedes-Benz is the fact that they will rarely leave you totally stranded, and it made it home with minimal problems after installing the Lucas, and in fact the transmission was able to hold together long enough to get me by for two months until I had time to swap it out! I am very proud of my Benz, but at the same time I wanted to know WTF happened.

Upon pulling out the transmission I noticed that the original casting numbers on the left drivers side of the casing had been ground off, and some other ones were imprinted in a somewhat imperfect way. It was very strange. Then I looked for the numbers on the right passengers side of the case where the pan meets the case, and to my supprise that area was totally blank! I have never seen this before and I will post up photos later tonight.

Anyway it got me to thinking maybe it was not the correct transmission. Even though it come out of a 560 I never really drove the 1990 using that re-maned unit. Upon inspecting the transmission I found that the bushing that stabilizes the torque converter had spun it it's bore and was solid copper. This caused the torque converter to flop about and seep trans fluid from the front seal. Very strange.

Having not rebuilt the original 722.350 transmission that come out of my 1991 560 originally, I was in a bit of a pinch. All I had on the shelf were two 722.324's out of early model 420's, so I said to myself "Fuck it". Ill give it a whirl, if anything just to see what happens because we are talking about my daily driver.

6.5 hours later the 722.324 transmission was mated to the 560 power plant. I installed new transmission fluid and was very careful to make sure it was not over-full. These transmissions need to be FULLY WARM before checking them. That means you need to get your butt out on the road and turn 10 miles or so before checking the fluid. Strange thing was that the same very odd flare between 1st and 2nd happened. What happened was that the transmission would rev up 500 RPM's before the upshift, but only during a certain amount of pedal deflection. I adjusted my kick-down (bowden for you picky guys) cable many times, one time I had it so taught that the 1-2 shift resulted in a very powerful and loud squelching of the tires. I was somewhat impressed and I bet the people at the gas station I drove past were too. Ultimately I had to settle for a shift point from 1st-2nd gear of about 2800-3000 RPMs to avoid the flair.

Now I am fully intending to rebuild the original 722.350 that come out of my 560, as all it really needs are new friction discs for reverse, however I will go on and replace them all while in there. What I will be VERY interested to find out is if by replacing the 722.324 transmission with the proper 722.350 that is rebuild will result in the 1-2 up-shift flare going away. It's entirely possible the vacuum modulator and or kick down solenoid could be causing this condition, but I haven't really had the time to research the differences between the two. I am also curious if perhaps the transmission from the 1990 560 that I replaced mine with originally could have been a later model 420 unit 722.355.

Some diffrences between the earlier and later transmissions that I noticed are this,

(1) The tab on the top seems to be a bit longer on the later models

(2) The mounting area for the flex discs have more square ends than that of the early model transmissions.

But nothing real major and all of them insignificant considering I am currently driving the 722.324 transmission in a late model 560 SEL. I have to admit that I beat the living snot out of the transmission right after installing it. I even put it on the highway at speeds WELL above... well... lets just say well over 3/4 of the way buried.

I did notice that the gearing does feel different in 1st to 2nd. The vehicle pulls really hard now in 1st on thru 2nd. So much in fact its almost a little spooky given the cold icy conditions at the time of the test. Top speed didn't feel effected, however I wasn't really paying attention to the RPM's because a cop had someone pulled over on top of the overpass that I went literally FLYING under at WOT.

I will say this... In a pinch you could use any variety of 1986-1991 V8 420 or 560 transmissions in your vehicle, but I think the 1-2 shift problem will plauge you should you use the non-proper model number for your year and make. It may be something as simple as a vacuume modulator, however I am considering changing the one from my original 560 trans to this one in an effort to vet the claim. I'll see what kind of work around that can be used in a "Pinch" just because at this point it has sparked my curiosity.

Ill post some images later tonight. I have a few other write ups I want to do before I go back out to the freezer (garage). Now I know I warned everyone what would happen if they used the improper part number in the post above, but I don't listen to anyone sometimes, including myself. In my defence I did state that it could be possible to use a earlier transmission in a later vehicle and vice versa but it would require modification. It appears that I have arrived at that bridge last week and now it's time to cross it.

Wish me luck.



-- Edited by SELLC on Thursday 27th of January 2011 06:16:58 PM

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LET'S GO BRANDON!

 



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It took me awhile to get the photos transferred over to the computer but here they are. What you are looking at is a factory re-man transmission from Mercedes according to the tag in the photo above.

Funny how no numbers exist on the lower passenger side of the pan where most all others do. And also very odd the lack of a 126 casting number in place of etched number.

Also look at that front torque converter bearing! Sucker was smoked! Even though the seal looked fine, the converter would wobble and weap out transmission fluid.

I am starting to think the small flare issue is something relating to the fact both my current transmissions are not 722.350 units, because I replaced my original transmission only because reverse went out, with no flare issues. Of course it could be a coincidence. The 560 didn't seem to have issues chewing up a Cadillac STS on the highway the other night, but I did bounce of the limiter on the hard pull from a dig. So we will see.

-- Edited by SELLC on Monday 14th of February 2011 05:09:37 AM

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A middle-aged loner on a crusade to champion the cause of the innocent, the helpless, the powerless - in a world of criminals who operate above the law.

LET'S GO BRANDON!

 



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Hello SELLC and other folks,

I have in my possession official MB information with regards to the transmission types 722.3 (W 4 A 040 ) & 722.4 (W 4 A 020 )...It's probably best to start with the meanings behind the numbers and letters etc etc.

Transmission type...This is what the meaning is behind the letters / numbers W 4 A 040 ...

W = Hydraulic Torque Convertor.
4 = The number of forward gears.
A = Version ( internal ).
040 = Maximum input torque in Nm.

Transmission Number...722.307...

722. = Automatic transmission for passenger cars.
3 = Transmission tpye eg. W 4 A 040
07 = Version, eg, adapted to the respective type of engine.

The Identification of a new transmission is as such... eg 1262700901 722.307 02 000761

1262700901 = Part Number for transmission without Torque Convertor.
722.307 = Transmission type.
0 = Independant for left-hand drive or right-hand drive.
2 = Automatic transmission.
000761 = Production Number.

This should help you folks out and at the very least indicate to you the relevance and importance of these numbers, especially when you require parts !

Also, when the transmission is changinging from 1st to 2nd gear, there's quite a lot going on inside the transmission, aswell as the other gears...And it also depends on whether 1st gear is actually selected on the gear-stick...However, I'll do my best to arrange an over view...

Gear                                Transmission                                                                                             Actuated elements                                                                                        Ratio

1st                            In front (Ravigneaux) and rear planetary gearsets.                             Brake Band B2 + Free-wheeling unit.                                                                      3.68 / 1
                                                                                                                                             (In driving positions 2", & B", clutch K2 is also engaged)

2nd                           In front (Ravigneaux) and rear planetary gearsets.                             Brake Band B2 + Brake Band B1.                                                                            2.41 / 1

3rd                           In rear planetary gearset.                                                                     Clutch K1 + Brake band B2.                                                                                    1.44 / 1

4th                           No transmission.                                                                                    Clutch K1 + Clutch K2.                                                                                              1.0 / 1

Reverse                   In front (Ravigneaux) and rear planetary gearsets.                               Disc-brake B3 + Free-wheeling unit + K2.                                                              5.14 / 1


So in realizing the above, it would appear that the application of B1, and / or the releasing of K2 were causing the issues that SELLC was experiencing, depending on his gear selector position. But things are much more complicated than that, as there are also several other hydraulic "pressures" that could be affecting the flaring that's being experienced, but more on that later ! Should SELLC or the Administrator wish to start a new thread, I have some experience with these transmissions, and the information to help anyone interested out. You only need ask ! Bear in mind though, Automatic Transmissions are really not for the enthusiast to try and repair at home, but there are some adjustments / tests that can be carried out relatively easily, to bring the transmission back up to scratch ! Or ultimately to lead you to the MB worksop !

Cheers,

Ratus



-- Edited by Rastus on Monday 13th of May 2013 02:23:22 AM



-- Edited by Rastus on Monday 13th of May 2013 02:23:59 AM

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FAR BEYOND DRIVEN

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Yo people,

Possibly a little known truth about your transmissions fitted to your MB, is that if you look at your speedometer, you will notice little yellow strokes / dashes on its face. These yellow lines indicate where the transmission shift-points are when gear-selector is in "D", and wide open throttle is applied. Too much variation in shift-points will indicate that a transmisssion service &/or engine tune-up is required at the minimum for your car. This will also reveal any possible wear & tear inside the transmission should exessive flaring &/or delayed up-shifting / hesitation be experienced.

Cheers,

Rastus

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"Only an alert & knowledgeable citizenry can compel the proper meshing of the huge industrial & military machinery of defense with our peaceful methods & goals, so that security & liberty may prosper together".    Dwight D.Eisenhower.



FAR BEYOND DRIVEN

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Yo people,

Should some of you be wondering when you've decided to change your transmissions oil & filter yourselves, why only 3-litres of oil came out, yet you bought 8-lires of oil to replenish the unit, it's because the remainder is still living in your Torque Convertor...There's a small drain-plug with a 5mm Allen-head that you need to unscrew on the Torque Convertor that you have to remove as-well to get the remaining old fluid out. You'll have to rotate the engine slowly and possibly use a torch to find it, and access to it may require you to remove a little plastic cover.

Once your ready to re-fill everything back up, pour the first container in, - ( 4.0 ltr size here in Oz ), then start the car before pouring the remaining required amount back in. This stops the oil / fluid spilling back out of the dip-stick tube and making a huge mess on your floor / drive-way. ( By starting your engine, the oil-pump in your transmission will begin to re-fill your Torque convertor ). Even if the level is a little low on the stick after pouring the bulk of the required amount back in, take the car for a 5 + mile drive and re-check the level with the engine running, and you'll find that the level will have crept up the stick from heat expansion. It also pays to use the gearstick and move through all the selectable gears to get the most accurate reading before and after you top-up further if needed.

Cheers,

Rastus



-- Edited by Rastus on Wednesday 5th of June 2013 10:01:13 PM

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"Only an alert & knowledgeable citizenry can compel the proper meshing of the huge industrial & military machinery of defense with our peaceful methods & goals, so that security & liberty may prosper together".    Dwight D.Eisenhower.

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