[W126 Coupe] tranny fluid

[Richard Hogarth]

Steve, 
I appreciate all of your knowledge and experience and I appreciate your
contribution to the conversation. I wish that I had development experience
as you did with the Cosworth. That sounds like it was really a great time. 
 
The fact remains (as I see the facts) that as seals in an automatic
transmission age and harden and begin lose their ability to seal, a couple
of things happen. There can be a major failure of the unit or 
Over time as the seals age and harden and parts wear, microscopic wear
particles get caked around the seals and actually increase the ability of
seals and O rings function. The old oil also reaches a saturation point as
to the amount of dissolved solids that it can carry. More and more junk is
deposited where the  fluid flows more slowly: around O rings and seals and
the pan.
Transmissions can function just like this for tens of thousands of miles.
When  clean tranny fluid is put into an aged transmission, the new fluid is
thinner and lighter and can carry lots of solids which has the effect of
washing those seals clean causing seals to leak and for the transmission to
suddenly fail. Lighter oils always dissolve or have a detergent action on
thicker oils. For instance: Never put a 5-30 or a 10-30 into an older engine
that has been running a heavier multi-visc or heavier straight weight. The
new lighter oil will dissolve all kinds of crap in the engine causing leaks,
scoring, clogging of screens, passages and filters. You must have seen or
experienced this yourself through your years of automotive and
enginedevelopment?
 
( I too have worked on all kinds of machinery from motorcycles and cars to
aeronautical machinery. I cut my teeth on racing Saab 3 Cylinder 2 cycles
and John Zeitlen Super Vees, Renault wet sleeve R-8 and R-10 Gordinis and
Austin Mini Gymkhana runs  back in the late sixties and early seventies all
the way to PT-6, T-55/56 Lycoming , Pratt Jt-3D and TF-33 Turbines /
Turbofans / and TurboShaft and Turboprops both professionally and as an
enthusiast. ) 
-RPH
 
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Steve Lemberg
Sent: Thursday, April 05, 2007 2:53 PM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] tranny fluid
 
If you have a transmission that is being held together by sludge your
problem is it can fail at any time anywhere with out notice.     I prefer to
choose the time and place to affect repairs if at all possible.     Saying
that dirt is what keeps an old transmission working is absurd.     The info
from TCI is great for their stuff and general knowledge but TCI makes
converters that are not usually in service the length of time many OEM
converter are that do have the fluid drained repeatedly.   
 
The many hundred RPM's with no oil is just not true, as soon as the engine
turns the front pump starts to develop pressure and feed the converter.    I
would say the amount of time it takes for the car to move while in gear
after a refill (don't ask how I know this) is around 8-10 seconds or 60
rotations at a 600RPM idle.     There is oil film on the internal parts
after draining and the few seconds of minimal oil is not a factor, the oil
is feed to the converter under high pressure form the start of engine
rotation or very soon thereafter.    The information posted is regarding a
new transmission install that has never been filled and run, the fluid
drained during a service does not remove every drop of oil in the valve body
and passages so the pressure is restored almost at once.
 
Doing a service with out following the procedures recommended by the
manufacture is your right however you are doing a disservice to masses of
people here who are not professional mechanics or skilled in repair and
maintenance work on their cars.    There are many Mercedes with automatic
transmission that have well in excess of 500K miles, very few a handful have
ever needed a converter and these were due to hard failures in the
transmission.     
 
I have been involved in operating and maintaining things that drive, fly and
float for about 35 years.     The range is rather broad from a 1936 Chevy to
Falcon jets and things in between like P-51 Mustangs and Cosworth DFV/DFX
engine development.     Disregarding standard operating procedures negates
the expected service life and quite possibly the failure mode of the item in
question.    I would not want to fly an airplane that just had a C check
done to some mechanics own short cut idea of an inspection and I wouldn't
stand for that in my cars service either.
 
Steve
----- Original Message ----- 
From: Richard Hogarth <mailto:R_Hogarth at Foundrycove.com>  
To: 'Mercedes Coupes Mailing Lists' <mailto:mbcoupes at mbcoupes.com>  
Sent: Thursday, April 05, 2007 11:21 AM
Subject: Re: [W126 Coupe] tranny fluid
 
Bellamy, 
That cuts to the chase, good points. 
BTW - Volvos ain't the only cars where old fluid is a make or break
difference.
 
 Now for the religious experience part:
If you drain the torque converter, you are running it dry for many hundreds
of RPMs while it fills up. The torque converter is a pressure pump, not a
suction pump. Until it starts circulating fluid, nothing else gets fluid
circulated and the Converter is running dry. If one were to purchase a new
converter, the warranty would be voided if you don't fill the converter
prior to installation.    
 
 

Size of Converter 
Number of Quarts 
			

13" 
5 
			

12" 
4 
			

11" 
3-1/2 
			

10" 
3 
			

9" 
2-1/2 
			

8" 
2 
			

7" 
2 
			
					
					
					
					
 
 
Also, the recommended service on some newer automatics is to not even drop
the pan on the tranny. Ford recommends that for the first tranny service,
the fluid gets suctioned out through the dipstick tube. It's the second
service where the pan gets dropped and filter screen changed. They don't
drain the torque converter at all. 
-RPH
             
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Mister McGoo
Sent: Thursday, April 05, 2007 11:04 AM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] tranny fluid
 
Oh?  half a bath?  Look at it this way...  how often do you change your
transmission fluid?  If you're only going to change half of the fluid at a
time by not draining the converter (an exaggeration... you're changing
considerably more than half), then change it twice as often, right?  But
ALWAYS change your filter, OK? 
 
Let's not turn changing your transmission fluid into a religious experience.
We have read how to check the oil level every which way short of while
driving at 50mph.  We have even heard that the dirt in your fluid might
actually be the only thing that is holding your transmission together,
('specially if you drive a Volvo).
 
Advice:  Simply follow the Mercedes instructions.  If you don't do it
yourself, take your car to a Mercedes specialist.  

OK?

-Bellamy

  _____  

From: mbzman560 at hotmail.com
To: mbcoupes at mbcoupes.com
Date: Wed, 4 Apr 2007 21:23:13 -0700
Subject: Re: [W126 Coupe] tranny fluid

Steve- I'd say amen to that.  Not draining the converter is like taking a
1/2 bath, or only draining half of your motor oil.
Camran


 
 

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