240D MT made loud noise
 

We were driving our 1982 240D MT when we heard a loud noise under the car and thought we had run over something. Nope. Then the MT developed a whine. we turned around to drive home and she wouldn't go into 4th w/o grinding and then she started popping out of all gears and then not engaging in any gears. we towed her home. This car runs perfectly otherwise and has 190K miles on the original engine and clutch. Is this a catastrophic failure of say a main input/output shaft or what? Ideas on R&R? We have had it for 15 years and do not plan to part with her. Are there rebuilt MT? I cannot find any anywhere.

Ever check the transmission fluid level since purchasing? You very well may have. Yet this can be the result of not bothering on a very old car. It also can just be wear. Not typical
at 190k miles though.

This transmission was also used behind the brands large V8s at the time. So the design is not weak. Personally I would just look for a used replacement. Depending on the year there are two examples. One is cast iron and the other aluminium. I would replace it with the one currently in place.

Sometimes the nut on the yoke can become loose. That does not sound like your issue. At least used examples can be found still. My guess and it is only that is you have lost a shaft bearing.

First inspect the driveshaft where it connects to the transmission. As mentioned, the nut that connects the flange on the output shaft may have loosened.

Check the linkages at the shifter and the left side of the transmission for excessive slop.

Catch/drain the fluid, if there isn't any or it looks really bad source a used transmission and replace the clutch, throw out bearing, clutch master and slave cylinder at the same time. Inspect the throw out fork for wear.

Good luck and drive on !!!

Thanks guys. I changed all the fluids when I bought it many many years ago and put synthetic gear oil from Amsoil about 5000 miles ago. Shifting was improved. I'm stunned really. I put a low mile 3.07 dif in a few years back and MPG went from 35-36 hwy to 38. I will pull it and peek inside. The Haynes manual has a good writeup on rebuilding it but I can't imagine finding OEM parts. I'm on the hunt for a low mile used unit and of course will do a new cltch/PP etc setup if needed.

I believe that transmission is supposed to use ATF vs gear oil. GL-5 is hard on yellow metals e.g., synchronizers, check the spec on which is used.

Saw the WTB, there is an aluminum case and an iron one. You may wish to specify your preference.

Good luck!!!

Thank you. I believe the MT oil was not a gl5 type but I am starting to learn the lesson: USE what MB says to useOEM. ATF is what was recommended of course. On this forum someone recommended Penzoil synchro as the best for these old MB gearboxes to be kind to the bronze inside. will do. I am looking forward to peeking inside to see what happened and will post the results. I have never heard of a total failure of a manual tranny. The noise was LOUD!

What bronze inside? I doubt any bronze metal was broken inside the MT. The loud noise probably was caused by a sheared gear. It happened with my 5sp Chrysler caravan years ago. Oil brand is not as critical as one made out to be. Good luck.

Well Barry you get the gold star for figuring it out. I pulled the tranny out yesterday. The clutch and PP look nearly new so will leave them. When I popped the drain plug metal filings and junk fell out, BUT NO OIL!!! It has been 8-10 years since I replaced the ATF with AMSOIL MT oil. Must have been a slow leak over 10 years and I have added only about 10K miles(I have 3 others). Stupid knucklehead idiot, you say. Yup. My bad. I guess the only way to kill a MT is no oil. On the search for a aluminum 4 spd 81-83 now.

No you are not a whatever you described. Our wives descriptions of what we are tend to be more accurate.

Modern convention is not to even check the engine oil for the majority of car users. For quite a few years.

Once a year for manual transmission and rear ends. Plus a quick check if any really very long trips are anticipated. If car is in use. Old cars are special.

Engine oil check and a quick peek at the oil cooler hoses. After every fuel tank fill is really important.

I am a firm believer that some addition of heavy oil to the rear outer boots. After purchase. Is both easily done and well worth the effort. The proven tendency to fail is on longish trips. Is eliminated.

Some of the original oil in them seems to escape over the decades. Usually you can save the originals if at the first notice of clicking. Get some oil into the boots.

These cars get ever older and we will probably see a rash of oil cooler hose failures all too soon unfortunatly. Out on the highways with the hotter weather.

Prevention is worth the effort. Many I suspect still have the originals in place. Well past a reasonably expected lifespan. Usually a failure will cost the engine.

The cv joint parts heat and expand with not enough lubrication and brutally drag themselves across each other. Ignore the clicking and the joints will fail.

HO:
Since you have an iron case trans that will bolt up, it may be easier to find a shifter for it than to find an aluminum trans.

The synchronizers are bronze/brass.