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R129 Automatic Transmission Fluid Shock?

54K views 154 replies 38 participants last post by  jmgsusa01 
#1 · (Edited)
I am almost ready to have some maintainance that will put me at ease. I purchased my SL back in September and have been prepping for one major stop at the indy I use for all my repairs.

Along with the brakes and springs already discussed in another thread I have already purchased Zerex G-05 antifreeze for a complete coolant change, I have no idea how old the one in there is.

Also purchased transmission filter, pan gasket and 8 liters of MB trans oil.

I have been reading the transmission threads (722.6) and from what I gather my 96 will still have the torque converter drain plug, so my intention was to fully drain the trans but I then came across a post saying certain MB techs only recommend changing the fluid in the pan so that certain solenoids/electronics don't go into viscosity shock.

Should I be worried? I never heard of this before. My SL has over 150K and I don't see any service records mentioning any type of transmission work in the records that the PO gave me, so if the viscosity shock is real, then my transmission would probably be a great candidate for this condition, if thats the case I will have the indy only change what is in the pan.

-Pete
 
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#61 ·
.....If I were you I'd do it, running on old fluid can't be doing it any good.
That’s what i’m thinking Richard. Just unsure about doing a full change as opposed to incremental fluid swaps.
I’ve got a day to mull it over before phoning my Indy on Monday.

By the way, you gave me advice a couple of months ago on fault finding with a blink reader, which I have now built into a ‘Mentos’ tub (Spearmint in case you are interested!). However, since swapping all of my fuses for brass ones, the problems have all been resolved!
Mind you, going by what I read on here...I will probably be using the blink reader some time soon.
:smile
 
#62 ·
Alan:

I faced the same issue with my ML320.

With over 200,000 kms on the original ATF Fluid, I finally did a 65% fluid change to minimize fluid shock.... i.e. having particulates accumulated in the tranny suddenly letting loose due to a complete fluid changeover and plugging up the fine holes within the tranny.

My local MB Dealer has stopped doing complete (100%) tranny fluid change-outs on high mileage MB's because of high tranny failure rates soon thereafter.

The good news is that I have 315,000 kms on the tranny, and it is still going strong.

I plan on doing another partial fluid drain again this summer.

The guys on the ML Forums have also adopted the practise of doing only partial fluid changes on high mileage tranny's with original ATF fluid.

God Bless, Arctic
 
#63 ·
Alan:
...My local MB Dealer has stopped doing complete (100%) tranny fluid change-outs on high mileage MB's because of high tranny failure rates soon thereafter.

.....The guys on the ML Forums have also adopted the practise of doing only partial fluid changes on high mileage tranny's with original ATF fluid.

God Bless, Arctic
Starting to think this would be the safest way to proceed. The fluid will still be getting changed, just over a slightly longer period of time.

Nice Igloo by the way!
:wink
 
#64 ·
Fluid shock would be of more concern in older transmissions where the shifting is hydraulically controlled using fluidic logic in the valve body.
So the fluid, besides doing lubrication, needs to be very clean with specific property to flow through those intricate passages and orifices in order to generate a very small differential pressure to move pistons, which would in turn open and close valves to let higher pressure to do the job.
For newer transmissions, the shifting is controlled by external electronic module/controllers, so the function of the fluid are mostly for lubrication.
 
#65 ·
Ray:

I hear you.

However, when even a MB Dealer won't do a complete fluid transfer on a 1999 ML320, due to fluid shock failures experience, there is good reason to only do a partial change on high mileage units with the original ATF fluid.

R129 Forum Member "MAVA" rebuilds MB trannies. Maybe he will chime in on this thread.


God Bless, Arctic
 
#67 ·
I did complete fluid change+ filter on my 91 W124(sold) with 233k,the car was having shifting issues 2-3 gear change, the fluid was nasty and sediment in the pan,also installed shift kit ,fixed the issue and drove the car for another 2 years then sold it for the SL purchase, also did complete fluid change+ filter on my 92W124 126K and 90 W126 160K,no issues at all.
 
#68 ·
This fluid shock is a total old wives tale - I have done plenty of googling in the last 7 years and have yet to see anyone with a transmission failure after changing transmission fluids (using the correct fluid!!).

What will kill any auto are these Jiffy Oil type power flush machines.

Visit the 210 forum and learn about the Yawling/Yummling? method of changing the fluid.

Both my Mercs were done this way and the transmissions at 200k kms are as smooth as silk.:grin
 
#71 ·
This fluid shock is a total old wives tale - I have done plenty of googling in the last 7 years and have yet to see anyone with a transmission failure after changing transmission fluids (using the correct fluid!!).



What will kill any auto are these Jiffy Oil type power flush machines.



Visit the 210 forum and learn about the Yawling/Yummling? method of changing the fluid.



Both my Mercs were done this way and the transmissions at 200k kms are as smooth as silk.:grin

Not true. After 30 years working in a dealership, I have seen fluid shock countless times. If you service the fluid regularly, like every 30k miles, you will be fine. We won't service a car that has high mileage and has no history of being serviced in the past. It's not worth taking a chance, unless you don't mind a potential overhaul.


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#69 ·
Just to chime in. I was going to do the 3-4 partial fluid change but ended up doing it in 2x. Dropped the pan, replaced filter and gasket, added about 3-4 liters of fresh trans fluid. The next time around we dropped the pan again and drained torque convertor also, again a new gasket and filter and then filled with all fresh trans fluid, something like 9 liters iirc.

The reason I ended up doing it this way is that if I only renewed say 3-4 liters at a time I would always have old fluid mixed in with the new. So far no issues doing the full changeover.
 
#70 ·
Here is the deal:

Everything Mercedes came with a "5 Speed" in +96, BUTTTTTT

+96 V8's & V12 came with first-generation 722.6's
96 I6 came with a 722.5
+97 I6 came with 722.6's
V6's came with first generation 722.6's in the R129's

On all first gen 722.6's a fluid test needs to be done to determine if a fluid change can be done, or just drive it into the ground, orrrr rebuild Now. If the fluid lost all it's properties...

Martin
 
#75 ·
When I first came to this site I kept hearing about "fluid shock" and thought it to be nonsense. How could changing new fluid for old harm a transmission? But what looney2ns said makes sense - if an owner has so abused his transmission as to not serviced it since the dawn of time, and the filter is so clogged that it cannot trap any more particulates (chiefly clutch material I believe) then new fluid could loosen that crap and clog some small passages.

As others have said if the transmission has been that abused new fluid probably won't help.
 
#76 ·
You have the four speed tranny, just replace filter and all fluid.
If you have a converter plug replace from there too.

Depending on mileage, like after filter replacement, 15K miles.
When I have the car up for service.

I many times empty the pan, measure, add new fluid, but no filter.
At 30K miles I will replace the fluid and the filter.

You are not going to run in to any problems.
Buy some Dextron III tranny fluid.

Get a power steering filter.
Replace that too.
While you have your hands dirty. Lol.

Use the same type fluid. ;)

Guys,
I am talking about the first generation.

Regards,
aam.
 
#77 ·
You have the four speed tranny, just replace filter and all fluid......
....You are not going to run in to any problems.
Buy some Dextron III tranny fluid.
Hi Albert,
Good to hear from you again. Hope you are doing ok.

Your information appears to make the whole decision as clear as day...which is what I have been looking for. This has been bothering me all day today.

Does your advice still apply to transmissions with no history of any fluid/filter changes having been done?
 
#78 ·
Alan, you really do not have much choice as yours is a '92 and it NEEDs to have good clean transmission fluid to function. With No history, you will just have to assume it was never serviced.
If you worry about fluid shock, then just drop the pan and replace the filter without draining the converter. Drive it for a while and do it again. Cost a bit more but give you a peace of mind.
 
#80 ·
Can you explain to me why my ’92 needs clean fluid more than the later 5-speeds boxes do? I would have thought that it would be equally important to them all. I have no experience of auto boxes, having only driven manual boxes in the past, so just trying to build up at least a basic knowlege of their foibles.

Although Albert said that I would have no problems if I changed everything at once, most on here seem to prefer and advise the partial change method, so that is what I will be asking the Indy to do. Always better to be safe than sorry.
 
#81 ·
MAVA did a great explanation on this subject, worth a search. IIRC the general gist was it was not changing the complete fluid that was the problem and new fluid did not cause shock.

The main likely cause of any damage was incorrect service procedure, resulting in the plates being dry of fluid for a given time. This results in loss of the coating if the transmission is run up to quickly or too long before the fluid has had chance to work it's way into all areas.

My Transmission fluid was changed completely as required and stated in the MB service sheets.

Any transmission specialist should be up to speed on the correct procedure for fluid changes as this is not something that only applies to R129's. My transmission guy just rolled his eyes when I asked the question, and said why would anyone want to leave old fluid in there.

My advice would be to take it to a Transmission shop and pay the 2hrs labour and get it all changed correctly.

I feel this fluid shock has become an urban myth a bit like the never jump start a Mercedes lol! MB give the correct jump start method in the handbook. I am of the opinion the module damage is done as a brown out trying too hard to start it when the battery is flat and not with the jump. MY2C :devil
 
#86 ·
.....May be you should check with your owner's manual and see if they specify the fluid for your car.
Unfortunately, it only says to use Automatic Transmission Fluid, with a sub note asking you to contact a dealer for the correct fluid, which I found strange as the handbook is quite specific on everything else.

The pdf though Ray is of great help in this respect. Many thanks for this, and everything else. Much appreciated.
 
#87 · (Edited)
Okay Gents,

Thank you for the kind comments! I do not consider my self an expert on transmissions as others in this world know information too... I have rebuilt many of these 722.6's, and I can say their are three to four(not gear ratios, or in different engines that mate-up) versions of these transmissions.

The very first version which is what the R129 has is sensitive like any other 90's 722.6 is!

What makes it sensitive is the "K2 bearing" is a bushing copper bearing, and once the lubrication is wicked-off the copper surface, and/or mating shaft. The pressure of load in nolonger on the shaft, but all the planetary gears, and needle bearings from the planets just start to eject, and mesh with the ring gear where the planetary gears ride on. Then it is self destruction, and one gets the "whine" in just about every gear position except for 4th gear. The 2nd Generation on forward have roller bearings for a K2 and it does not care of 100%(fluid exchange) new fluid or 30% fluid(pan only fluid change).

Yes, a old first Gen 722.6 can be updated to current generation. I do it all the time, but I use W220 transmissions for the V8 and V12 cars, yet I have use the old transmission case as the +2nd gen 722.6's have Touch Shift, and it does not work with the electronics of the first-generation. My 98 W140 has 2004 W220 transmission internals in the 1998 shell. All of this to get the roller bearing k2 which the internal shafts are a different sizes.

"fluid shock" is merely wiping - off the lubricant of K2, but the fluid exchange does not mater on +2nd generation 722.6's or any other Mercedes tranny...

If one wants to contest "fluid shock" it is when the torque converter is drained. That is the worse time as no fluid is in it, and the bushings are running dry on any transmission. Plus no fluid to pressurize the fluid galleries in the transmission which pressurizes the clutch packs to enable gear engagement..

One says how do the re-builders of transmissions doit? they fill up the torque converter with a few quarts of fluid during assembly, so everything is wet right away...

I do fluid exchanges on everything except these first generation 722.6's as one day it works, and the next day "crash of the planets" ....

Hope it makes sense?

Martin
 
#90 ·
.....I do fluid exchanges on everything except these first generation 722.6's as one day it works, and the next day "crash of the planets" ....

Hope it makes sense?
Martin, thankyou for your explanation on the cause of fluid shock. I now have a clear understanding of the problem.
However, can you elaborate on why you won’t touch a first gen 722.6 please.
I am assuming that this is what is in my ’92 500SL, but if you won’t go near them, with all of your knowledge and experience, is it wise for us to attempt to be doing what you won’t?
 
#91 · (Edited)
The 722.6 came in 96, very different than the trans in your 92. I think your trans uses standard ATF Fluid and has service intervals so personally I think you are over thinking things. Change the fluid. If you are worried change three or four liters during your next 3-4 motor oil changes and then do a full change on your 5th oil change.


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#92 ·
The 722.6 came in 96, very different than the trans in your 92.
]
Oh...ok Pete. Thanks for keeping me right. Don’t suppose you would know what transmission was used in the ’92 models by any chance?

Starting to think I should have just bought a space shuttle instead. It would have been less complicated!
:grin
 
#104 ·
Mo' money

OK guys I think I get it..... fluid shock is a Mercedes form of PTSD... right?
When doing the transmission change do not forget to check the electronic conductor plug ($14) the seal seems to leak after a while and could cause problems ... I would change it out for good maintenance. Also, make sure your shift seal ($10) is not leaking, this may need to be changed after 15+ years. This seal leaks little, but is annoying. The electronic conductor plate ($180) is known to be problematic and after a while should be replaced in many cases after 15+ years. Hope I haven't put a damper on this thread!
 
#105 ·
Gentlemen,
All my info. was/is for the first generation, like YOU have.
Four speed Hydraulic Tranny =722.3 with a V8.

I think that V12 and AMG uses the same tranny.

6 Cylinders does NOT.

Dextron III from Shell or other reputable name brand.
If you have doubts, get it from the dealer.
Or at list, call them.

722.6 and up is an other story.
They claim that the fluid is for life.

Yeah.
Right.

So far I have drained the converter to all my cars, only once. With no problems.
I will replace the filter every 30K.
Every 15Kmore or less, I drain the pan fluid.

Now you and I know, that the O rings will dry up, some parts wear faster....
So you will have to rebuild...

(Make sure that you replace the rear main engine seal.) ;)

If this happens, and it will.
So if this happens.
Don't blame the fluid change.

Regards,
aam.
 
#106 ·
Here is a quicky what benz has what:

mercedes transmissions

Here is what the first-generation 722.6 has for a K2 bearing:

New one:

Input Shaft Bushing - 68410-01 - Sonnax

Damaged one(note the copper is worn-out):

Third and fourth photo on post 14:

http://www.benzworld.org/forums/w140-s-class/2212618-722-6-slip-shudder-d-r.html#post10759265

First and second picture on post 27 too:

http://www.benzworld.org/forums/w140-s-class/2212618-722-6-slip-shudder-d-r.html#post10800033

The K2 damage in the pan:

first picture(post4), and planetary gear damage as the result of the pan parts

http://www.benzworld.org/forums/w140-s-class/2212618-722-6-slip-shudder-d-r.html#post10721553

Second to current generations of the 722.6 K2 bearing:

Bearing & Seal Kit - 68410-02K - Sonnax

All the best,

MArtin
 
#108 · (Edited)
The information in your first link is wrong. It shows the SL320 as having the 422.5 up to and including the 1997 model year when in fact they got the 422.6 in the latter part of the 96 model year. I have to assume the rest of the chart is filled with errors also.

Instead of looking stuff up which may be wrong or going by what someone may think is correct, the easy way to see if it is the 722.5 (hydraulic) or 722.6 (electronic) is this.

One way to tell is if you have PNRD432 label on your shifter, you have the 722.5 hydraulically controlled 5-sp transmission. The 722.6 would have PNRD4321
 
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