to flush or not to flush, that is the question
 

When I got my 83 SD in may of this year [2003] I really had no idea what to do first, it needed so much work that I did the easy things first. One was flushing the tranny. I un- hooked the return line to rad on driver side and placed the line in a 5 gallon pail. I then started car and with the fliud going into the bucket I began adding new fluid as fast as the filler would take it with out overflowing. The fluid was dark, not real dark, like black, but sort of brown. After the fluid began to feel cool, about 4 gallons in the pail, I figured the flush was complete. I topped it of and went for a drive. It shifted much smoother than before the flush. To make a long story short I just finished flushing my tranny for the forth time and it gets smoother and smoother every time. The question is: Am I nuts? or can flushing a tranny with 230,xxx miles keep getting better and better. The 4 flushes were over a 7 month period. any and all comments welcomed. steve

Steve:

Save yourself a bunch of money and just drain the pan and torque converter, then refill with Mobil 1 ATF after replacing the filter and cleaning the pan.

No need to actually pump the fresh tranny fluid through it, it's wastefull.

Peter

peter, I hear you on the waste, but our shop has a waste oil heater so it really is not wasted. I read that the mobil 1 atf doesn't work as well on a older tranny's .Please correct me if I'm wrong. I pulled the pan and cleaned it and put in a new filter during the first flush. steve

Yes, this was an unnecessary step. Draining the trans AND converter, changing the filter and filling with fresh fluid is the best approach.

Something very important to point out here is the SMELL of the fluid is probably a better indicator than the color. If the fluid is nice and red, there's no need to smell. If it is brown or black, smell it. If it smells like turpentine or varnish, then your clutches are burned. Under these conditions an aggressive flush can often wash out the clutch linings and the car won't move.

If the fluid is brown, but smells okay, just change filter and change ALL the fluid.

Good luck,

YALL SAW THIS COMING
 

Suck about a quart of trans fluid out the top... put in a can of Trans-X and either put it in all the gears for about 20 minutes.. or drive 30 minutes ( or more ) .. THEN do as the above posts have suggested... this will dissolve any varnish which has been deposited and then you flush it ( hot but DON'T get burned )...

Mobil 1 is superb tranny fluid. Often makes an older tranny run better (with the proviso that any fluid change on a nelgected automatic can take if from bad performance to none - the only thing making it work is the crud, dissovle the crud and it quits).

A complete fluid change is all that is needed, and fresh automatic transmission fluid is VERY expensive fuel!

Peter

Peter, You are advising AGAINST dissolving any varnish which has been deposited in the auto trans valve body before draining the fluid ? :eek: :confused:

I'm confused!!!! steve

Using Trans-X seemed to save my Suburban transmission.
At about 70k it seemed to slip and not down shift properly in OD when starting up hills at highway speeds. After using Trans X and changing fluid a few times in 1500 miles, problem went away. It now has 104k with no problems (yet). Product seem to clean & flush, but previous transmission fluid never smelled or was other than red.

I don't know if I was reading Peter wrong... but all my experience and many statements by others and pure logic would indicate that getting the varnish out of those small holes in the valve body of an automatic transmission would be a good thing.. then drain to get it out of the system.. just like we drain oil out to do the same thing..
It is also cheap ( typically under $10 ) and I have never heard anyone claim they thought any damage occured using it ...
Varnish is not supposed to be in those tiny cavities with those little balls that control the hydraulic clamping at the right speed and power of the clutch bands in an automatic trans...
I do not have any indication that this is a matter of new fluid being able to dissolve Deposited Varnish... thus I think something like Trans-X to get it off... and into the stream ...making it possible to completely remove it from the transmission via draining... is needed....
Steve, does that help ?

Leatherman:

Usual problem is that the varnish is all that is holding the friction coating on the frictions, so the tranny stops working when you dissolve it. Steel on steel isn't the best clutch in the world -- that's why trains have sanders.

Varnish is also sometimes all that is closing the check ball orifices -- dissolve it and too much fluid goes past and bad things happen. Can also produce too much clearance in the valve spools so that the control system won't work.

Automatics can be tempermental beasts.

Peter

Too slow an activation of the hydraulic movements which engage the clutch bands is the same as a person not letting out a manual clutch in a normal fashion... and it causes greatly increased wear of the friction surface...
I can not agree that the continuation of clogging those small holes in the valve body is a positive affect of varnish build up... and what is likely to happen is the small steel balls in that unit get stuck and don't close or open like they should...
You almost talk like the original engineers bored the hole too large... and we should or need to have varnish from old trans fluid to make it work properly...
I vote NOT :D

I think I understand more now, great explaination. I still wonder why my 230,000 mile tranny would shift smoother and smoother with each flush. I really know nothing of the magic that goes on in an automatic tanny but I do know that mine is working better than ever[since may 2003]. I am now driving my 83 SD without tranny fears and that allows me to enjoy this fine automoble even more. steve

Steve:

Well, you aren't going to HURT it by flushing the tranny, for heaven's sake, just waste perfectly good tranny juice.

Watch out for the smoother and smoother, though -- MB trannies traditionally shift firmly under power, so if you are getting very smooth shifting at wide throttle, you may be aquiring slip instead.

Most people don't change the tranny fluid anywhere near often enough -- and old fluid will cause varnish on frictions and control passages. Eliminating this stuff will make for better operation.

Peter

Yes, the flushing will indeed clean passages in the valve body and that's, of course, a good thing. But, that's not the whole or most important issue here.

A really gunked up transmission, as psfred properly pointed out, has its clutch surfaces basically held together with the crud. Chemical or pressure flushing can, and often does, remove the clutch lining material and renders the vehicle immobile.

Again, SMELL the fluid, before doing any kind of chemical or pressure flushing. If it is brown, not black and does not smell like varnish or turpentine, then change it and be happy.

Going to whatever length to keep an engine crankcase clean has no downside if done with good, common sense. This same mindset will NOT always work with an automatic transmission.

My $0.02,

You are trying to walk a pretty fine line there Larry...

If cleaning the varnish out of the valve body also causes the clutches to come apart due to taking out the magic sealing varnish..

Then the transmission needed rebuilding.....

Come on, let's show a little common sense here. You can't flush one without flushing the other. If flushing risks losing the clutch surfaces which necessitates rebuild, this is a no brainer decision. You don't flush it. It's as simple as that.

Why would anyone risk a total rebuild so that the valve body works a little better? Is it better to have a transmission that is not shifting perfectly or to have a transmission that will not move the car at all? Seems like a very simple decision to me.

Happy New Year,

COMMON SENSE ? PLEASE ,DO !
 

" has its clutch surfaces basically held together with the crud. "

I just do not believe this......

If that is true then do you have some place others can buy " crud" to put into their transmissions to keep their clutch surfaces working longer ?

It does not take but one happenstance of something having occured AT ABOUT THE SAME TIME as another thing for stories to get started about them being related...

When in fact many things happen temporally close together IN WHICH THERE IS NO CAUSAL RELATIONSHIP....

Do you have any Empirical references/data/tests to support the above statement...?

This is the reason Science is not based on ANECDOTAL stories... that controlled comparison tests are used to come up with good advise...
---------------------------------
I am not suggesting ' flushing' in the sense of using clean self powered fluid washing.. but just Trans-X and then draining and refilling... for the record....

Guys,

This is becoming an ominous thread. The originator reported by cleaning his transmission with an admittedly unique procedure that his transmission began working better. The major objections I heard from those responding was that he wasted a lot of automatic transmission fluid. From all the stories about how difficult the resealing of the pan is on these transmissions, and the fatal to the transmission consequences if it should actually leak at a significant rate while you are driving, say, 600 miles on a single tank of Diesel, make this odd approach possibly more interesting. This is how I service my power steering systems - basically a drain and fill operation that continues until the fluid coming back from the system looks like it came out of the can - and it works there, and if I am using an extra quart of fluid than is absolutely necessary, I don't care, my steering stay tight and that is the point. So, stevelewis may waste transmission fluid, and his procedure never addresses the filter (which I do change in the power steering analogy whenever I change the fluid, about every two years) but it is better than doing nothing, which is, strangely, what the W210 vintage and later transmissions require according to MB (and if you elect to change that fluid, you won't waste a gallon or two of it on purpose as it is very expensive).

The debate this has spawned about what happens when a machine with failed parts operates seemingly ok for unexplained reasons and then fails completely when someone services it is interesting but will likely never conclude. If something is working for reasons other than the way it was designed to work, it was actually broken regardless if it was "working" or not. The servicing, which would normally be considered beneficial for a machine operating as designed, cannot be "blamed" for the failure that was previously not apparent even if they occur in seeming sequence.

Engineers design things to work a certain way. It is wonderful if the design and then the manufacturing procedures result in a machine that can still perform some functions when some items are failing or have failed. These are not operating conditions included in the design as no machines are designed to include unnecessary parts that can just wear out or break without any consequence. There are many reasons for this lack of extra junk in machines, but the most prominent one is that these items always add cost (and mass) which are detrimental to sales. And sales are the reason the engineers got the task to design the machine in the first place.

Dirt, varnish, burned transmission fluid by products and other foriegn materials are not included when the transmission is built at the factory, and any transmission relying on the accumulation of these foriegn materials in strategically important locations to operate is already broken. If it is operating it is about to expire and any number of events can occur to bring about its demise. Servicing the transmission in a way that is beneficial to a machine operating the way it is designed may disrupt such chance arrangements of random junk necessary for the failed transmission to work, but so could a pothole encountered at just the right speed and angle, a very hot day, shaking at start up, or just plain gravity over time, and so on.

In the end this subject is not worth a big argument. Machines like automatic transmissions shouldn't exist in the first place. So who cares how they fail, right? Good luck, Jim

Which is why I want a reasonably simple way to put a manual trans in my 300D. It would then very quickly become a *perfect for me* car.

My only other option is "downgrading" to a 240d.. And it would actually be cheaper to do that than replace the trans in mine, as it will need at some unknown point.

Personaly I'm going to continue to change fluid and filter, and am in the process of running with a quart of trans-x in there for a few weeks. Just on principle, or out of spite, whichever way you want to look at it.

WoW, thanks Jim, thats pretty clear. steve

Yep, this is why I drive manual transmissions as well.

Go to any auto transmission shop or dealer, talk to the guys in the service department and I can promise you that they will back up what I'm saying about flushing a transmission with burned fluid. No anecdotes here, just plain old experience in the shop.

Happy New Year,

:D

Larry, If I go into a transmission shop I would be talking to people with a vested interest in OTHERS not keeping their transmissions clean and in good shape...
They have a vested interest .... MONEY... even if they think they are being honest.. their memory can be affected by the fact that they will make more money from neglect of transmissions than good preventative maintenance....

AND,

They do not get a representative sample of transmission examples to work with ... people bring them a skewed sample...transmissions which are giving them problems... and with too few " N " in statistical terms ( number that each shop or each man can be assured meets the criteria which we are discussing ).. to make an informed decision as far as policy...

And the fact is that ALL of the opinions which I got from those peope would in fact be ANECDOTES.. by definition... not a controlled study of the situation...

Yeah, I'm sure that you're correct. It's certainly a conspiracy theory. All the transmission shops and dealer service departments are run by aliens.

I'm just not smart enough to figure it out. Thanks for the help.

Happy New Year,

It's well known in the auto mechanic business that an automatic tranny "not working right" is a bad candidate for a fluid change. Quite often, it's ONLY working because the fluid is bad and its crapped up -- the shifting symptoms are from sticky spool valves. Nice flush and clean fluid is definitely a crapshoot -- quite often the tranny fails very quickly when the varnish and scorched friction material washes off -- there is then NOTHING on the frictions and it won't move.

Standard frictions are high density paper, by the way -- this is why water in the tranny fluid means instant death, the paper "melts" pretty fast.

Best advice I've heard on automatics (refering mostly to GM turbo 350/400s) is to use semimetallic frictions instead of standard ones. Much longer life, impervious to water, much less damage from slip (they won't char), but do shift harder.

If the tranny works better, hey! Change the fluid every 30,000 miles like you are supposed to, and it may last forever (not really, the frictions eventually die).

When it does, though, it ain't gonna bet a quick set of clutch paks and seals repair, though -- usually by then there is serious mechanical wear too.

Peter

Great synopsis JimSmith.

I had an old 220D transmission fail about 1,000 miles AFTER I changed the very old and very cruddy transmission fluid after I purchased it. Its not hard for me to believe that new fluid dislodged old varnish deposits and these deposits pluged up something in the valve body that controls the shifting process that lead to "failure". I agree with Jim that this is not the fault of the transmission - rather its a case of prior neglect coming to light after the recommended service procedures are performed - maybe for the first time ever.

All my current cars get 30K fluid and filter replacements - they do because I've had them for 100K miles and I know the fluid is in good shape.

If I acquired a 230K car that had crappy fluid I would NOT change it - I'd drive it until the trans failed, rebuild it and then begin changing fluid and filters on schedule.

Tim

Thanks Peter. I was being accused of spreading "anecdotes."

So maybe it's not a conspiracy by the auto repair industry after all.

Happy New Year,