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  #1  
Old 10-06-2003, 10:26 AM
Coming back from burnout
 
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85 Mercedes 300D Automatic Transmission Lifespan...

As my 300D approaches 300,000 miles, I am wondering about the longevity of the auto transmission. My engine still doesnt lose a drop of oil!!!

Once in a while, my trasnmission makes me nervous....

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  #2  
Old 10-06-2003, 11:08 AM
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It should. I was considering buying an early 80's TD which had been maintained by Stu Ritter. It had about 200k on it. When I called them to discuss its maintenance history, they assumed that in that time the transmission would have needed to be rebuilt. I guess that means that the expected life according to experienced mechanics is less than 200k.
I also looked at another early 80's TD which had had its transmission rebuilt around 100k.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
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  #3  
Old 10-06-2003, 11:10 AM
GottaDiesel's Avatar
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IMHO --

80% of the life-span of an auto-trans (which I hate -- but will be forced to deal with if I find my 300D) is determined by the driving habits of the person. If you hammer it/beat on it -- life is short... you get the picture.

20% is based on the actual design, etc.

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  #4  
Old 10-06-2003, 11:16 AM
fz500sel's Avatar
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The 1985 300D....

that I owned had over 300K and the trans had never been rebuilt according to the P.O.

He bought the car when it was new and always took it to the dealer. When I bought it off of him, I went to the dealer and looked thru all of the service records. No tranny work ever except for regular maintenance (fluid and filter). I had the vehicle for 3 years and never had any tranny problems except for a cooler hose leak.

During those 3 years I was often nervous about the possibility of the tranny finally giving me some problems after all those miles.

I pulled into a 7-11 about a month ago, and first thing I noticed was the nice 300D in a parking spot there. After looking at it more closely I realized it was my '85 that I had sold. The guy I sold it to came out and got into it and when I stopped him to say hello I saw that he had put another 5k on it. I asked him if he had any problems and he stated that it was still running in tip top shape.

It says something for MB longevity.
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84 500SEL EURO 101K ( JUST LIKE MY 1ST WIFE. GLAD TO GET RID OF HER! )
85 300D 310K (sold)
90 350SDL 184K sold
83 300D 118K (sold)
88 300E 153k (sold)
93 400E 105K (sold)
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  #5  
Old 10-06-2003, 12:46 PM
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I think that the service interval for the auto trans will make a lot of difference in the life.
I think I saw something that suggested changing the auto fluid and filters every 30,000 miles.... American cars used to suggest every 50,000....So I expect many of us are not following the guidelines the factory recommends... or the cars are 'new' to us and often we don't know how often the fluid and filter were changed on the trans....
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  #6  
Old 10-06-2003, 04:12 PM
Marshall Booth
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The longevity of MB 722.3/.4 series transmissions depends on how and where they are used (and I'm not entirely sure what ALL of the relevant variables are). Stu Ritter reports that it's rare for them to reach even 200kmi in Denver. In Pittsburgh 250kmi is about average, but many 300D/SDs have provided 300-400kmi of service - most of those have a LOT of highway miles and much less city driving time. Transmissions wear MOSTLY when they shift. In my 10 years of weekly commuting from Pittsburgh PA to Washington DC, I've shown that the number of shifts on a small engined diesel (190D 2.2) even during highway driving is nearly double that of a larger engined diesel that's more powerful ('87 300TD or '87 190D 2.5 turbo). Twice the number of shifts should produce just about twice the wear (and small engined MB automatics DO seem to go thru transmissions prematurely - many only lasting 150-200kmi or so vs cars with somewhat more powerful engines going nearly double that distance before requiring a rebuild.

Marshall
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  #7  
Old 10-06-2003, 05:02 PM
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"Transmissions wear MOSTLY when they shift"---Marshall
True,and points out the importance of clean fluid in the system... since any build up of varnish in the small holes which used to control the speed/power of the engagement of the clutches affects the amount of wear per shift...
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  #8  
Old 10-06-2003, 05:42 PM
Marshall Booth
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Mercedes recommends ATF service intervals (fluid AND filter INCLUDING draining the torque convertor) every 30kmi under "ordinary" conditions (that means highway driving in temperate weather). In harsh conditions (city driving or cold/wet weather or in dusty conditions are HARSH according to Mercedes) the fluid should be changed at 15kmi intervals with the filter changed at 30kmi. Longer intervals will result in faster wear.

Marshall
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  #9  
Old 10-06-2003, 08:39 PM
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My 300SDL had the original tranny that shifts flawlessly at 321k miles. My 85 300D that had 475k was on it's 2nd transmission. From my experience, MB automatics in diesels usually last 250-300k. Gassers are less, maybe 200k.
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  #10  
Old 10-06-2003, 10:32 PM
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Ideally a transmission in cruise mode has very little wear at all. Mainly the planetery gearsets as the clutchpacks and bands are, or should be locked up completely by hydraulic pressure holding them in gear. Transmission friction materials wear during shifting. Suprisingly a soft shift wears more than a firm shift as slow engagement of clutches/bands smooths out a shift but allows more slip and therefore more wear of the friction materials in doing so. A firm quick shift is preferred. obviously this is only up to a point. Banging hard, harsh shifts are hard on parts from shock loads and hard on friction materials from the sudden engagement. It should be obvious that a maladjusted transmission will wear faster if allowed to flare, slip, etc. The other great killer of transmissions is heat. Everyone knows about those little o-rings on the oil filter housing cover rod that get all brittle and no longer seal? Well imagine that X1000 with all the seals in a 20yrd old transmission. This is what products like Trans-X address besides varnish and crud removal. They contain seal-swelling and softening agents to attempt to restore flexibility and therefore sealing ability to these hardened old seals. A vehicle that has been used to tow, carry heavy loads or drive in heavy traffic extensively has more of a chance of having heat damage. The transmission fluid is cooled by passing through the radiator. In most cases this is adequate. However when towing, heavy stop-n-go, etc. fluid can easily exceed +260*. This kills the lubricating qualities of the oil and cooks the life out of the seals. ATF is supposed to have some seal conditioning agents in it so changing is regularly will help keep seals alive. ATF will also break down just like motor oil at high temps depositing sludge and varnish in the transmission that causes other problems. This is where synthetics offer an advantage. They don't break down at high temps, so no sludge/varnish. This also means they retain their lubricating qualities longer. RT
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  #11  
Old 10-06-2003, 10:49 PM
mb123mercedes
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Hi all.

I have also noticed that lots of MB owners
will take their(car) tranny's to a tranny place and
most don't have a clue on how to maintain
them correctly,some have even diagnosed
them as needing rebuild because they where
slipping,but the only thing the tranny needed
was the modulator valve adjusted or replaced.

Thus causing the owner paying for a rebuild or
new trans and not needing it.


Louis.
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  #12  
Old 10-06-2003, 11:34 PM
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My '85 just turned 155,000 miles (250,00km? ) and is on the original transmission. I changed the fluid around 150,000 miles and there was no clutch or other material in the pan or on the magnet. I hope it goes at least 200,000 miles before needng anything. I have the modulator set a little on the "firm" side to reduce wear. Sometimes the vacuum bleed valve and/or vacuum amp is a little testy, but no mechanical problems....knock on wood.
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  #13  
Old 10-07-2003, 12:39 AM
lrg lrg is offline
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My '85 has almost 160K miles with over 100K of that going up and down some pretty big hills here in S.F. No problems so far. I have done the 30K oil and filter changes religiously and recently converted to synthetic trans fluid.
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  #14  
Old 10-07-2003, 04:18 PM
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Thumbs up Living on borrowed time? Maybe, Maybe not...

My 95 E300D (same basic design as your transmission) is all original with 324,000+ miles. I recently purchased the car, and was quite surprised (and a little disappointed actually) that it had never been ‘gone through’. The car had been dealer maintained its whole life, including fluid changes at MBZ recommended intervals.

That being said, almost all the mileage was accumulated by highway driving. The transmission works very well, except for one small (nit picking) problem on the 1-2 and 2-3 shifts: as it releases one gear, there is a small hesitation before the next gear engages, but it is NOT a flaring problem – it seems that it takes a fraction of a second too long for the clutch pack to fill up completely, and/or piston(s) to move. Probably an indication of the seals becoming less compliant & not holding pressure as well as they would when new. I’ll probably try to increase the modulator pressure a little bit to see if it helps…

Glenn

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Current rolling stock:
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+
1995 E420 135,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
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