Tranny Flush? - PeachParts Mercedes-Benz Forum

imagesinthewind · #1 10-21-2012, 02:48 PM

So, I bought the 78 with a very small, tiny tranny leak.

I don't think it's gotten bigger, there is only oil under my car. I check by
wiping my finger across the spots and checking for red.

I do add tranny fluid every couple months, not a lot, but enough to keep it between the lines (yes, at temp, running check).

It's been sitting through the summer, I've been scooting around to save $$ and diesel is over $4 here. I got and installed a new brake master and have been driving it daily.

When I first start driving, the tranny takes a click to get into gear and it's pretty slow to start (tranny has always liked a warm up period before moving though) and is slow to change into second. It doesn't rev really high or surge, just slow. And other small funky things. When it warms up, it seem to be fine. It upshifts fine, then downshifts fine.

I was thinking of doing a tranny flush and all new fluid. But I'm afraid with a small leak that the pressure of the flush will make the small leak bigger.

Any ideas you'd like to share about the tranny in general, why it may be slow to upshift into second? Currently the tranny is showing a level right between the two lines, so I'm good on fluid.

Thanks!

oldsinner111 · #2 10-21-2012, 02:53 PM

your modulator could be leaking,and vacumm sucking it up.Flushes are bull****.Drop the pan change filter,gasket.

EDBSO · #3 10-21-2012, 05:56 PM

Not certain about yours by my w210 is designed to shift out of first at a higher rpm when cold. MB did this to help the engine warm up quicker and to reduce pollution emissions.

If it shifts properly when warm you are probably OK if you keep the level up.

vstech · #4 10-21-2012, 07:33 PM

yeah, NEVER use those flush places... just drive up on ramps, slide under there, and pull the two drain plugs, one in the pan, one in the torque converter. then I also pull the cooler hose connections, and drain the cooler too. gets ALL the fluid out. then drop the pan, change the filter, then clean the pan with brake spray, then put a new gasket on the pan, and put it all back together.
fill the trans with 4 quarts of fluid, and start the car, then add 1/2 quart every 10 minutes checking the level, stop when it gets to the lowest line and go for a drive to get the fluid fully up to operating temp, then park on the levelest spot possible, and get the level perfect at the top line.
done.

JHZR2 · #5 10-21-2012, 10:45 PM

What I would do is get a vacuum extractor and pull, say, 1 qt of ATF. Replace Then do this again after a few miles.

Im not sure the exact amount that you can vac extract from the dipstick, but go for that amount a few times.

After replacing 10-12 qts of fluid, you should have 60+% new fluid. Let this circulate and refresh and clean to the best of its abilities. Then drop the pan, replace the filter, and put all new fluid in there.

THis gets you starting slowly, and you can go from there. If you want, clean the whole AT real well and try the baby powder trick to find any leakage.

You dont want to introduce too much fluid too fast in case something that is easily solvated and dispersed does.

Lots of people do replace fluid via the cooler line. Ive never tried it.

compress ignite · #6 10-22-2012, 02:06 AM

What
VSTECH suggested...

It's the Only SAFE way to "Service" an MB Tranny!

JHZR2 · #7 10-22-2012, 05:58 AM

that is too rapid an intro of new fluid for me on an unknown at. one with known good history, for sure.

vstech · #8 10-22-2012, 06:53 AM

so, what is the point of gradually changing a quart of fluid at a time?

JHZR2 · #9 10-22-2012, 08:39 AM

Quote:

Originally Posted by vstech

so, what is the point of gradually changing a quart of fluid at a time?

Well, do you know any of the history of this AT? I dont. I see a car with 265k, who knows if and when the AT was rebuilt, and a trans that is exhibiting funny shifting and leaks.

I totally agree that a pan drop and everything you mentioned is the right approach for an AT that is a known quantity with some history. I dont know the history with this.

Ill bet you have heard of the shops that wont service high mileage ATs, or people who service their transmissions and then they dont work right. Was there something wrong there before? Likely yes, but too rapid a change can make it worse. Why? New fluid will have a far different characteristic in terms of additization and oxidation level. This means that it will clean, disperse and solvate deposits at a rapid rate, and can innondate the filter and other components.

Noplace am I saying that your approach is not valid. I just wouldnt go that route immediately, especially since with new fluid, any cleaning that will occur will immediately lodge in the filter, and so then you just did the job and just loaded the filter up with all kinds of junk.

Putting a good quantity of fresh fluid in gradually and easily from the dipstick (KISS principle) ensures that it gets in, a good quantity of fresh fluid is blended, it can start to clean and disperse, then load the old filter, and finally after getting a decent amount of new fluid in there, then after some mileage, the pan can be dropped and the job done right.

To me it is just a more secure way to get this done, allowing things to be done gradually and not impacting stuff in too rapid/severe a way. Thats when things get clogged up or too much junk loosened.

Back in the old days (2003-ish?) Larry Bible or someone used to swear by Trans-X, IIRC, as a flush to use if things started getting funny. But there were lots of discussions back then about doing gentle, slow and methodical changes first, and it has always been a sound approach.

The aspects of failure and degradation in an AT are far different than in an MT or an engine, diff, etc.

chasinthesun · #10 10-22-2012, 11:05 AM

Ive Never had a bad experience with steps mentioned by vstech ,I do the TC first since since its up frt ,then the pan ,the other way youll be fighting drops of trans fluid coming down as you fiddle with the TCs bolt.I can say that the pan gets treated to a tank cleaning since I dont want anything but clean parts going back on.Its the first service I do when picking up a used diesel mercedes,Im some 20 cars in with these steps with never a bad experience only good .I change the filter and fluid before recommended mileage requires ,20k when 30k is the Service allowance.Once a yr for a daily driver is the norm in my garage.

charmalu · #11 10-22-2012, 03:12 PM

First I heard of this one qt change therory.

That could also apply to the eng oil, Glow plugs and....

When changing the baby`s diaper, only remove a portion of the cr@p at a time or the balance of the system will be disturbed.

what ever works.

Charlie

JHZR2 · #12 10-22-2012, 05:23 PM

Quote:

Originally Posted by charmalu

First I heard of this one qt change therory.

That could also apply to the eng oil, Glow plugs and....

When changing the baby`s diaper, only remove a portion of the cr@p at a time or the balance of the system will be disturbed.

what ever works.

Charlie

No, they are entirely different systems and the mechanisms of failure are different.

Well, actually for glow plugs you could just replace the bad one and keep going.

Not saying it is the end-all, be-all decisive thread, but a fast google search gave me this one, talking exactly of the issues that some speak of:

Changing ATF in high-mileage car that has been neglected... - Maxima Forums

Note, I am in no way saying that the method that VStech is advocating is wrong. My cars that have known history get exactly the service that we are all talking about.

But if you are denying that the additives and properties change over time, or that fresh ATF will have a ton of detergent and dispersant in it, you are just kidding yourself.

So the issue is that there is varnish and possibly sludge in there, dirt and gunk on surfaces and seals, friction material, etc., not to mention just how oxidized the ATF may well be if it has been left in there a long time. ATF is notoriously destroyed by shearing very fast and to a substantially different fluid.

So you put a ton f new fluid in there, a new filter, and it goes to town solvating junk, carrying it to the filter, cleaning surfaces, changing the frictional characteristics of the clutches, and it all happens abruptly, so that the mechanical adjustments or electronic ones cant adapt and be tweaked.

Then you get a nice loading on your filter, which impedes flow.

And you leave it in there for 30k miles before you change it out.

See what Im getting at? Slow and methodical for cleaning and solvating dirt is the best. Making monor changes that allow dirt to slowly be carried off, preventing tons of junk from going through valve bodies and small orifices is a good thing.

If I dont know the history of an AT, slow and methodical is my approach.

If I know the history, go at it.

Ive never had an AT fail me yet, while many cant keep them past 150-160k... I must be doing something right... Whats the worst? A little wasted ATF? At least if I suck it from the dipstick, Im getting newer fluid in the AT, faster, and more often than if I wait for a pan drop, which is also a good thing...