Greg, do you recommend this stop leak for the older 4-Speeds (84 Euro S) too as I have the same leak through the torque converter grate. Is this better /safer than something like Trans-X that seems to have good reviews on Rennlist as well.

Also, by chance do you have a warped or damaged/dented trans pan you want to sell cheap? I'm looking to get one for a project (not a project car). If so pm me. Thanks.
Pete

 

I haven't personally used Trans X.
I generally find a product that works for what I need and then don't try a bunch of other products.
That being said, I've read that Tran X is more aggressive and have read of seal failures, resulting from this.

I can certainly can find you a transmission pan.
What version do you want to play with? (Send me a picture GregBBRD@aol.com.)

I once sent a pan to Hans, to see if his CNC guys would be interested in building a replacement aluminum pan.
Apparently, because the pan sloped in two different places, it wasn't practical to do.
So, like so many things, that idea went nowhere.

 

Great overview of the difference between an automatic and a manual!

 

This the stuff?

 

Continuous 1st gear starts pounds out the "rear" planetary gearset/driveshaft assembly.
I see this in the '85/'86 928 transmissions.
And as the torque from both Mercedes and Porsche engines increased, the problem would just get worse.

Although difficult to imagine, my conclusion would be that the engineers knew what they were doing.

 

Doesn't my 84 4 speed start in 1st on its own, and the 2nd gear start thing happened later?

 

Yes.
Their claim that a fluid can "renew worn bands", is a bit "over the top".
And anyone who knows **** from shinola knows this isn't going to happen. (Did I just "date" myself?)
What actually occurs is that the seals and O-rings swell up some, less internal leakage occurs, and more pressure can get to the bands and clutches. (Increasing clamping force and reducing slippage.)

 

Yes.
'83-'86 did this.

 

Thanks will try this. Good points everyone.

 

So the Porsche engineers equipped the 928 with a transmission that could not handle first gear starts, they realised their error after the 85/86 models and then made the MB 722.3 tranny function the same way MB intended it and as installed in their S class limo's? Even so those "bright boys" still made sure the thing could start off in first as long as you minced the throttle and did not think to put a note in the owner's manual cautioning against excessive use of this?

Not sure what kind of engineering that would be but it most certainly would not meet my acceptance criteria- if a tranny cannot handle first gear starts it has no place in the car no matter who designed it and I do not believe that is the case at all. If it was your superb torque monsters would rip 2nd gear to shreds surely?.

Your statement of observation is of course most interesting and pertinent but without meaningful analysis what does it actually tell us? Does every example of that vintage show the same characteristic wear patterns- viz age, mileage etc etc or is there a random scatter? Is the driver a factor in the pattern? Are the ones that wear more serviced less than optimally? - It is one thing that something shows signs of a problem it is another matter analysing why and what to conclude from it.

If there was a clear and obivous trend with S4 and GTS models having been adjusted "out of spec" showing clear and obvious premature degradation i might be a bit more concerned but frankly even then the way both my 928's have operated I would gladly accept some service life attrition such is the difference as to how the car feels when driven. If I had to tolerate the dreadful stock S4/GTS auto presentation I would have walked away from the thing 20 years ago I felt it was that bad and there was nothing wrong with my examples- all the ones I have driven all felt the same - somewhat tired or lethargic even!

Setting off in first gear the way my tranny is setup has to be a lot easier on the box than setting off in first the way Porsche intended it to be operated [foot to the floor]. There are no wheels spinning, no drama at all unless I want to force matters some and even then with wider rubber than stock and the superb for its day PSD there is no drama it just hooks up and goes. The thing changes gears exactly as and when I want it to and frankly it is a deilght to drive.
If you do come across a S4 or GTS auto tranny that has excessive wear on the 1st gear it would be appreciated if you can share details of such. My research suggested these units are potentially good for 500k miles. If my tranny holds up to that I will be nigh on 200 years old by the time it is shot!

 

Fred:

How you can make statements about subjects that you have absolutely no idea about, continuously amazes me.
I've had dozens and dozens, if not hundreds, of these transmission apart and rebuilt. This gives me an excellent overview of what occurs and why.
You've had how many apart and rebuilt???

Starting in 1st gear, consistently, pounds out the rear planetary.
Period.
There's no debate, no "well it shouldn't be that way".
It is a fact.

I went out out my shelf of transmission pieces and grabbed one. It's an '85/'86.
While not terrible, it shows, very clearly, what occurs. (That "pounded triangle" raised area should not be there, but that portion should be perfectly straight with the other side.)
I've seen GTS transmissions with the kickdown jumped which have that shaft spun 90 degrees....



Easy to see where the corner of the shaft retaining plate is pounded from 1st gear starts.

Note how all of the gear shafts have been thrusting and rubbing on the inner planetary gear.

I was once told that the AMG transmissions had a stronger plate here. I've never been able to very that, however.


And I have no idea of where you are doing your research, there's absolutely no way one of these transmissions will survive untouched for 500K miles.
That's not an absurd statement, it's just plain old silly.

 

Greg,

First of all thanks for the pics at least it gives some idea where physical damage is taking place and if you can offer any insights as to how it was concluded first gear starts cause that it would be very much appreciated, what mileage such happens at and what if any untoward signs indicated there was an issue- that or whether such was found by chance when you opened the box.

I've had dozens and dozens, if not hundreds, of these transmission apart and rebuilt. This gives me an excellent overview of what occurs and why.
You've had how many apart and rebuilt???

Baffled as to what prompted the above comment- at this moment I am trying to mechanically understand the issue and what if any lifespan reduction I might expect to see as a consequence of running the way I do. I am not asking the tranny to do anything MB did not design it to do and for sure there are no outward signs of any distress.

How you can make statements about subjects that you have absolutely no idea about, continuously amazes me.

Any comment I make I welcome any challenge from anybody anytime - that is how leaders develop their knowledge base. If you have anything specific in mind please feel free to articulate.

Easy to see where the corner of the shaft retaining plate is pounded from 1st gear starts.
Note how all of the gear shafts have been thrusting and rubbing on the inner planetary gear.
I've seen GTS transmissions with the kickdown jumped which have that shaft spun 90 degrees....
It is easy to see the signs of damage but not easy [for me] to see how 1st gear starts cause this given my current limited knowledge of the auto tranny.

And I have no idea of where you are doing your research, there's absolutely no way one of these transmissions will survive untouched for 500K miles.
That's not an absurd statement, it's just plain old silly.
That number I wrote was a typo- I typically convert metric units to dinosaur units for you Stateside chaps but simply forgot to convert to miles. As for source of info my number comes from Bill Ball's S4 that covered 500k km before having problems and Bill is as reliable as they come and that with his driving style and an Eaton blower fitted a good chunk of the time. As I recall there was even a claim some time ago about a 928 that allegedly covered something like 600k miles unmolested but no proof of such. On the other hand in Germany these transmissions were rated as being capable of covering 600k miles before needing major rebuild when in MB vehicles but not sure that qualifies but they are generally reckoned to be the best in class for that vintage and by some margin. As an FYI see the extract I post below.

Finally and perhaps of more relevance, I have experienced the effect of the vac line ceasing to function and the transmission "thump" on part load changes is horrific. If there is one contingency I have seen that feels as though it could cause mechanical damage to the tranny that would be it- however if it did cause damage i have no idea at the moment how or where it would manifest itself - doubtless you will have a position in that regard.

 

Fred:

So, what yo don't know:
Those particular gears, shafts, and plate are only used in 1st gear, so any damage is a result of using 1st gear.

I'm not sure if I have the severely pounded assembly from the GTS which is manually shifted and started in 1st gear its' entire life....but I'm far too busy to go and look for it.
If I run across it in the future, I'll take a picture and post it.

Mileage and years since new are both a factor in automatic transmission life.
I'm guessing that if someone put 500,000 or 600,000kms on one of these 722.3 transmissions with-in the first 8-10 years or so (and most of those miles were "road" miles, with minimum reverse gear use), that may have been possible.

But with 30-40 years of time since new, the "gig" is up. The rubber O-rings and seals are toast. And low internal pressures, as a result of this, absolutely destroys parts.
The clutches and brake bands start slipping (slightly, almost undiscernible, at first), creating excessive heat. This excessive heat creates hot spots on the drums and the clutch plates, making replacement necessary. Add a minimum of $1000 to replace these parts (or the "flat rate" guys will grind down the hot spots, reducing the clutch surface area, to save money.)

The first sign of 'hardened" internal O-rings and seals?
The O-ring around the oil pump leaks fluid to the outside. (See the OP.)

Patch it and delay rebuilding it until the internal damage gets so severe that the transmission no longer functions?
When the parts double, triple, or go tenfold in price, again? (This has occurred at Mercedes and Porsche over the past 5-7 years.)
Or rebuilt it when it should be rebuilt, and use it for another 30 years (if one uses Mercedes pieces and not "offshore" pieces and doesn't cut corners....like grinding down "hot spots" on the steel parts of the clutches.)

Expert/high quality transmission rebuilders know what is happening.
What was that saying?
"Pay me now or pay me much more later!"

And as far as I can recall, the highest mileage example I've rebuilt had 250,000 miles on it.
....And I've done a boatload of these at under 150,000 miles!

 

Edited

 

For what it’s worth, the 5-speed is only of true value when installed in the CS/GT variant as those are more of a muscle car mindset and the whole dynamics are changed (including engine, coding and suspension settings). For day to day driving and enjoying the 928 for what it is, a true Grand Tourer, the automatic fits its personality and useability best. Like Fred said, the MB 722.3 is an amazing transmission that is rock solid and performs very well for a 300HP car.