[Rich_1971_280s]

Hi all, I have searched on this subject and haven't had much luck. I am contemplating undertaking a DIY rebuild of my 1971 280s auto transmission which packed up on me earlier this week.

I am no stranger to a engine rebuild and other extensive restoration and rebuild work, but have never opened up an auto box before.

I am looking for resources, printed, online or otherwise and someone who has done this before who might be able to guide me, or put me off altogether.

Is this a fairly straightforward auto box? Can I expect to order my parts, dissasemble, clean, replace, rebuild and re-install or are there some tricks to this that mean I should steer clear.

Since more is always better when it comes to info. Here's the situation, in case a full rebuild is not necessary.

I've only had the car for two weeks, my first Mercedes, and my first auto. I have noticed the past days driving that normally my oil pressure gauge is pegged at 3. I assume this is normal, I have no idea. Anyway, this particular day I notice it's dropping slightly at idle, a little lower every few times I inch forward in traffic but comes up full when I move. This worries me, and I decide ok, if I can make it a mile I can stop at a garage.

Well, I hardly made it around the corner of the intersection before a loud thump sound, one I can feel, and then no power, as if it's just been dumped in 4th or I don't know what. I pull over immediately and switch off the ignition thinking I just blew the motor.

I had the car towed home and called one of our Mercedes specialists here in Cape Town. I explained the situation and he asked if I have tried to turn the motor over since then. I say no, but I go out and crank it. It fires immediately to life, full oil pressure, and I sigh in relief that the thump was transmission not engine.

I call them back, ok, engine runs as normal, now they ask did I try to move the car, but no, of course I didn't shift it out of park. So I go back and now it won't even turn over at all, as if seized.

So, my assumption is that whatever is wrong with the transmission is stopping the engine from turning, but the engine is probably still fine, it did run no problems just before I tried for the second time.

I'm also assuming a 40yr old automatic needs a full rebuild regardless of if this is as serious as I assume it is or not.

Any help, wisdom, insight is appreciated.

Rich

 

[Grubeguy]

See the online resources portion of this forum - there's stuff posted about the transmission.

When I bought mine, the tranny was slipping pretty badly. I took it to Aamco and got it rebuilt for about $2000. May or may not be an option for you, but the major tranny guys can still fix the things...

 

[wbain]

There is a transmission manual in Vol 2 of the MB Classis car CD, ie the W110, W111 manual.

My advice is to take an auto trans course at a local community college that has an automotive program. This way you can be informed about how they work and the way everything fits.You will need some special tools for this, like a special spring compressor to compress the planetary gear set to remove the internal plates.

You will probably find that the clutch plates are fine on one side and bare on the other. Parts are available from the classis center. There is a thread on The International M-100 Group in the 6.3 section on rebuilding one of the larger transmissions and they are very similar to yours.

 

[Rich_1971_280s]

Thanks wbain,

Any idea if the tool is available from Mercedes Classic Centre also?

I'm not going to jump into this lightly and I will take the advise here very seriously.

I will check for a auto transmission course locally. The thing is I want to learn, so paying a shop to do it doesn't teach me anything, not to mention the fact I don't have the cash right now.

Thanks for the help! I will talk to the Classic Centre.

Rich

 

[wbain]

Please check this thread:

lots of naked 6.3 transmission pics.

http://www.m-100.cc/forum/topic.asp?TOPIC_ID=4432&whichpage=1

Please remember that the M100 trans is heavier duty and slightly different than the smaller ones.

 

[GGR]

I don't see how your engine oil pressure would be related to a transmission failure. Anyway, oil pressure can be as low as 1kg or 15psi at idle with a warm engine with no problem as long as it peggs back to maximum as soon as you rev the engine.

I would take the time to do a precise diagnostic before taking the trans out and tearing it to pieces. It could be something else.

 

[Rich_1971_280s]

I don't see how your engine oil pressure would be related to a transmission failure. Anyway, oil pressure can be as low as 1kg or 15psi at idle with a warm engine with no problem as long as it peggs back to maximum as soon as you rev the engine.

I would take the time to do a precise diagnostic before taking the trans out and tearing it to pieces. It could be something else.

I imagine they are unrelated, mechanically they must be. It was just interesting to me to note that for the week since having the car, the pressure gauge was always pegged at 3 all the time at idle and driving, cold or hot, but this changed just minutes before the problem occurred. There was a definite progressive loss of oil pressure over a three minute period from just over 2 down to 1.5 at idle. It was just an observation that I thought might mean something.

 

[Rich_1971_280s]

Maybe it's the motor after all and not the transmission at all.

 

[GGR]

When the engine is cold engine oil pressure could be around 3, but lowers when it gets to its working temperature.

Does the engine rotate? Try with a 27mm socket on the krankshaft front bolt.