zekgb

Dammit I was all psyched up for dropping someone else's tranny for a change!

Bill Ball

No, not noticeably. It was just a brownish tint. I didn't see any fragments of brake band material either. I still have the old fluid, so I may take a closer look at it. Blackstone offers an analysis. The only problem is I contaminated it with carb cleaner.

Schocki

The quiet but noticeable whine is absolutely normal in P or N and is mentioned in the MB 722.3 manual. What you hear is the front planetary gear in free rotation. All clutches and brake bands are disengaged, everything is fine.

Mercedes Benz
"Complaint: slight grinding noise in selector lever in "P" or "N".
Cause/Remedy: this is a normal rolling noise of the front gear assembly which cannot be eliminated."

Because the sound was gone before, I think something was stuck (actuator or piston?) and works correctly again. Good news

My GTS always had the same whine in P and N. When my B3 (reverse probelm) gave up, new ATF fluid turned blackish/brownish within no time. But no smell of burned material. I think something was dragging and what you found in the fluid is some friction material.

Kiln_Red

Great news, Bill. I'm not too terribly surprised. I guess a transmission can fail in any way, but usually there are warning signs. The way the fluid smells has been the best measure for me as to the health of a transmission. The transmission fluid in my Buick Park Avenue looks brown, but it smells fine. I'm afraid to change it as I know it has never been changed before. 257k miles and still running strong.

Gonzotiki_666

Glad to hear that the car cut you some slack Bill!

Speedtoys

You lucky sod...

dr bob

All that clean living finally pays off!

Buy a lottery ticket. You'll only need one.


For those playing at home, there's an obvious case here for more frequent fluid and filter changes. Bill drives his car like he stole it, shifts manually a lot, yet manages to still be driving as the car comes up towards 300k on the meter. It's pretty easy to forget the secondary fluids sometimes, especially if the car isn't a daily driver, until an ugly symptom reminds us about what they do. Waiting for symptoms is not the best plan for extended life. Kind of like waiting for a rod knock to remind us to check or change the oil in the engine. Most times, there's already damage done that new lubricant won't undo. So keep a log of hat you do, and consult that log as you plan services for the car. If your car has ahibernation period, do thses fluid services immediately --before-- hibernation so contaminants can get out before storage time.

Bill Ball

As dr Bob said, frequent fluid changes are a good idea for the tranny. Tranny and brake fluid changes are often completely neglected. I'll admit to not changing brake or tranny fluid in family cars for way past their scheduled interval. The family SUV finally developed an ABS fault that was fixed by a brake fluid flush. I've been better with the 928, following the schedule pretty closely. With recent life changes, I lost my service bay, still pictured in my avatar, and regular maintenance has suffered. Still, I was surprised the tranny had 40K mile old fluid. Although it is now shifting well over all, I do plan to do a short term fluid and filter change in a few K miles and will pull the valve body then and maybe get a look at the B2 brake band. I did see the B3 band 40K mile ago and it looked like brand new, but the B2 has been much more abused, although less so recently.

BC

What lift was that?

GregBBRD

As much as some would like to believe....there are no "super" duty parts inside your transmission. It has the same pieces as everyone else's transmissions....and the clutches do wear out. (More than the brake bands, generally.) The "burned" fluid is, very simply, from slippage. That's the only source of friction to increase the transmission fluid temperature.

If I get these things apart and replace the seals and clutches at an early mileage (80,000 miles and 30 years), they generally have not "cooked" the steel plates that go between the clutches and they are amazingly economical to do (because they don't require as many expensive parts.) (I'm doing one with 70,000 miles on it, as I stopped to write this.) If I get them in the 150,000 miles range, generally the steel plates between the clutches are "toast". While the huge majority of rebuilders simply take a 90 degree sander and "sand down" the hot spots in on the plates (to save money and increase their profit margin) this is an incredibly poor thing to do. It simply reduces the available surface area that the clutches have to grab onto, which accelerates the heat problem even more. This is "used car lot fix it enough to sell it" stuff. Steel plates with hot spots need to be replaced.....like Mercedes says. The price of the steel plates has increased 1000%, in the past few years. Plates that we used to buy for $6.00 are now over $70.00....each! If one replaces these (like should be done) the cost of rebuilding the transmission goes up.....simply by definition.

Much beyond 150,000 miles, the drums that the brake bands "compress" onto begin to have hot spots....and then they need to be replaced. Once you start needing to buy "hard parts" (like the drums) the cost of truly rebuilding one of these things goes up astronomically.

Don't miss-understand me. The "flat rate" guys that "repair" these things for low dollars can still "repair" one for low dollars....they are never going to replace a drum.....regardless of how bad the hot spots are. They are going to use Chinese made clutches and brake bands. (I have these parts, too....for the people that are not interested in having a transmission repair that will last for another 30,000 miles....I have a huge cross section of different customers.)

However, if someone really wants a "rebuilt" transmission...that requires the replacement of "cooked" brake bands, clutches, steel plates, and drums (if necessary) with genuine Mercedes parts....and that stuff is getting really expensive, quickly.

Simply because of the cost of parts, I'm not a proponent of dragging every last possible mile out of a transmission, flogging it until it no longer functions. The internal seals and O-rings are rock hard, now....even if you are pouring in a "seal softener" like "Trans X". The rock hard seals and O-rings reduce the available pressure to the clutches and the brake bands, which increases slippage and wear to clutches that are already worn and deteriorating. Heat and increased slippage increase rapidly, when both of these things occur.

Automatic transmissions are the "poster child" for "you can pay me now, or you can pay me later". Get them early and they are economical. Wait too long and they get stupid expensive. Get a "flat rate hack" to "rebuild it" with low grade parts and pieces with hot spots.....and you will get to pay to have it done twice.....once by the hack and once by a true "rebuilder". I know....because I get then in to "rebuild" after some hack has "repaired" them.

Speedtoys

Greg:

My trans there might be well abused..any photos of crapped out stuff in there you can share with others?

gladyswoodhams

Heart breaking.

GregBBRD

That's probably a great idea. What to replace and why is the thing that takes so very long to learn. A "primer" with pictures might be very helpful.

Obvious to me, for many years, is the fact that "rebuilding" anything totally depends on one's definition of "rebuilding."

People take engines apart, don't do a valve job, don't replace the bearings or the rings, basically clean the pieces and put it back together. Some call that a rebuild. I call that a "reseal". And there's a huge difference in the long term results between that and a real "rebuild".

The "typical" transmission rebuild by the "flat rate hacks" consist of a new set of gaskets and a new set of clutch discs. I also call that a "reseal", not a rebuild. Yes, the clutch discs get replaced, but those are paper and virtually part of a "reseal".

In the end, the end product one gets back is totally dependent on how "rebuilt" is defined.

Pictures might help people know the difference, be able to ask intelligent questions, request different pieces, and get a better result.

Kiln_Red

Greg,

Wouldn't the transmission be noticeably slipping or have some other symptom(s) before the hard parts would be compromised? Logic suggests to me that the clutches are still the weakest link here and that they would need to be pretty well torched first before catastrophic damage to the hard parts.

My logic may very well be flawed. Thanks in advance for any further clarification.

BC

I have been doing a ton of research into automatic transmissions because that is what my towing truck has. The 4L80E. People are "rebuilding" these units with new clutch plates, but not replacing the "Steels" - and short distances later, there is some other problem and they have to take it out again. When they take them apart, I think the home mechanic expects some massive issues to be visible, when its apparent issues when driving are really all the little clearances adding up from just being generally worn. So the "hard parts" as Greg suggests need to be mic'd carefully and replaced when out of spec.

Again, just the differences from "Doing it Right" - which of course is a mix of spending the money and having the experience, or in the absence of experience, the ability to find the info you need.