I have a 1979 Mercedes 300SD that stopped going forward recently. It now makes a rattling sound all of the time (when running), engine RPM does not change when you put it in gear, etc. I had a couple mechanics whom are aquaintances of mine come over and breefly inspect the vehicle and the transmission is not pumping fluid. One bet on the pump in the transmission and one bet on the torque converter. Either way, the transmission needs to come out.

I have the Factory Workshop manual CD but it does not include the procedure for tranny R&R nor rebuilding. I have found the procedures on this forum for the W123 and W126 chassis, can I assume they are the same? My chiltons manual says I should drop the Enging with the tranny, is this necisairy? One of my mechanic friends says it isn't.

How much of a good idea is it to drop the drive shaft at the same time and replace all of the bearings (including U-Joint bearings)? I have replaced an automatic transmission on a Ford van before, and I have taken the transmission out of a Porsche before, but never a Mercedes, any advice is appreciated.

Thank You.

PS- If it is the pump in the transmission can that be replaced without tearing the whole transmission apart?

PPS- Should I re-seal the transmission when it is out?

Give me a little background on what led up to this, any weird noises, recent trans service ect. ect.

Also is the car in good condition?

Tabor: Yes. The front pump can be serviced without complete disassembly of the transmission.

Remove the complete exhaust system, the exhaust heat shield and the driveshaft. Then remove the transmission. Leave the engine in place and support the rear with a wooden block between the frame and lower crankcase.

You can remove a cooler line and place the open end in a 2-litre plastic bottle and have assistant start the engine. If the front pump is good, you will have fluid flow.

I have seen forward clutches fail and cause this problem.

You have a flex coupler front and rear with a center-support bearing in the middle. There is only one u-joint and they seldom go bad. I recommend replacing the center support AND bearing while you have everything out.

Test the fluid flow as described above and get back to me....Bert

(Zcode400@sbcglobal.net)

We just got the car in June. The previous owner did a fluid and filter change before selling it. No noises that my wife can recall. Car seems very well kept, but I don't really know. Very nice cosmetically.

I just worked through the same problem on my 80 300SD. Dr Bert's advice is valid. I suspect the front pump or TC or both are ruined. On disassembly, I found the "fingers" on the TC had sheared off and ruined the front pump so both had to be replaced. Not sure what caused it.

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

When you say "complete" do you mean from the exhaust manifold back?

One of the mechanics who looked at it checked the fluid level in the transmission, then started the car, then checked the fluid level again and said that there was ZERO difference and that meant that the pump was not pumping fluid. The other mechanic concured that the fluid would have dropped at least a quarter inch if the pump was going. Either way, the transmission has to come out.

EDIT- Thank You for the help.

One of the mechanics that looked at my car owns a transmission shop and said that this is common for this model (116) of Mercedes, although he did no know why. He said I would have to replace the torque converter and maybe the pump.

Thanks all for the help.

I would do the diagnostic prescribed by Dr Bert first- disconnect one of the lines at the radiator and start the car. I don't think you will get any pressure there. But if you do ,it's something else. It's too easy to check this first and you will have to take a line off anyway when you pull the tranny.

Yes, you need to take down the whole exhaust system, but it is easy once you get it disconnected from the manifold.

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

does it go fine in reverse? If so, it may be the B2.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

No.

However, I have a question: Do I need to unbolt the torque converter from the flex plate before I take the transmission out, or can I do it after?

Doktor Bert & rs899,

I have already disconnected everything from the transmission except the drive shaft, and I don't have any more fluid at the moment if I did want to reassemble and try the diagnoses, so I will forego the additional diagnosis, even if it would be a good idea.

PS- I got the exhaust out, thanks guys.

UPDATE: The transmission is on the ground.

A big thanks to everybody that helped me.

To answer my own question, I wouldn't have needed to unbolt the torque converter to get the transmission off, but I chose to. However, I guess anybody that knows anything about automatic transmissions would know that.

The torque converter tangs are broken off in what I guess is the transmission pump. I am going to start a new thread in a second asking how to get the pump out.