I have wanted a 300SD for a while now. I got impatient before when looking for one, and
foolishly bought a nice looking 380SEL that didn't run (was told it was a fuel problem
and it did seem that way), and I learned the hard way that the 380 is not a car with any
demand or even worth fixing really. It still sits in my back yard, partially apart, a victim of
the infamous Mercedes V8 timing chain problem .

II just found "low cost" 300SD, 1981 with 260k or miles. The transmission is bad they say.
I did my research this time before a purchase and the symptom (reverse gear only, lost
forward while going up a hill) seems to be the B2B piston breakage problem.

Now this car is not that close to my location. It has high miles, but I am told it runs
great. I read that if you managed to get a trans with this problem into 3rd gear, it
would drive. While I am not going to risk trying that to get it home.. as I'd hate to
find out it was a broken band, as it exited the transmission case.

I first had a thought that my 380SEL trans would fit the SD, but I have read here that
isn't the case. But I could use the SEL for other parts. I read that the updated servo
piston and parts costs about $100 from the dealer. The car is probably 80-90 miles from
my house. I don't own a tow rig. Say I was to find someone to tow the car for $200 or so,
or maybe even rent a truck and car hauler trailer... what should I be paying for a 1981
SD in this condition? I have played with automatic transmissions a bit.. even rebuilt a
chevy trans years ago, without much to work with. I know the Mercedes transmissions are
a lot more complex, but someone here said their 300SD or the same year I think, had this
problem and they fixed it without even dropping the trans pan. The procedure takes only a
few hours even with dropping the pan, another article says.

The thing is, while it sure sounds like I know what the car needs to drive, and the pics
of the car look pretty good.. I also don't want to have 2 Mercedes sitting around broken,
but I can't afford $3-4k or more for a nice specimen with no problems. Actually, I need
another vehicle to drive soon, as my old Toyota finally gave it up and I let that one go
to someone else's care after over a decade of good service.

Any thoughts on whether this one is worth the chance?

If the car is real nice and the motor is strong ( no excessive blowby) but only a bad trans, and price is right (maybe $1500 or less) you have a find. If you replace the B2 piston, make sure you also replace the sleeve in the case that guides it if it is still thew original aluminum type.

The asking price is $500.

From what I have read, it is almost certain that at least the B2B piston is bad, and likely that is the only problem with the transmission as far as it not moving under it's own power.

I'm actually toying with the idea of attempting a fix where the car is now, or nearby. I'd much rather spend what would be the tow money, on parts.


I would replace:
B2 Piston
B2 seal ring
plastic bushing for updated B2 piston
seal that holds in the bushing

You have it right about what needs to be replaced along with the B2 piston BUT you 1. Need to see the car and decide if you really want it (that sounds pretty cheap) 2. Recognize that you must be EXTREMELY CAREFUL about keeping the inside of the trans from getting contamination in it. How far away is it? If it were me and the car ran I would have a buddy go with me and drive it home. If you need to tow it a long distance you should be disconnecting the driveshaft anyway. You don't know what you are going to run into trying to fix things far away from home. Believe me, I've done it many times (mostly when I was much younger) - wouldn't recommend it now. Removing that sleeve is NOT necessarily easy with the trans in car but it can be done. I made a tool to do it but doing that properly far from home is more adventure than driving/towing home IMHO.

I have done trans work before, under less than ideal conditions
(like you, a long time in the past). You're right, it is cheap. But then again I was reading here last night someone on this forum has bought a few 160k SD's with bad trans for $200 each. The owner says a friend is a MB mechanic so they are using that as a price for a new transmission. Used ones go for $650, and of course the cost to R&R it. It's the old cost to pay someone to repair vs just buying something else, which this owner says he did. I have a few pictures, taken just yesterday, but of course they can't tell the whole story.

As far as wanting the car. The exterior looks good. I'm told the engine runs good. The tires are near new, and the wheels are the later chrome versions. The interior is blue, which to me looks kinda "different" (ok, ugly) against the woodgrain inserts. So it is not the car of my dreams (I like the palomino color if my SEL better), but if I could get it going cheap enough I could drive it for a bit and if I found a car I liked better. I even have the SEL that I think needs to be a parts car, and if I wanted to I could even use the servo from it, although it is probably original too.

My daily driver actually died a week or so ago and now has a new owner. That leaves me looking for a vehicle, and vehicle-less unless I rent one. I could do that, or rent a truck and trailer to haul the car, or pay someone to tow it. I would expect the cost to tow to be maybe $200. The map sites say it's about 70 miles from me. I don't really have anyone to help me with this. This is in SoCal, where so many are all about "me me me", and most people I know moved away.

There is public transportation that I am told goes near where the car is. The owner says the car doesn't move at all, except in reverse. But it is also facing uphill at the moment, from the pictures from yesterday. If I thought I could get it into 3rd and drive it, I'd take the ride up there.. have the owner pick me up, and if the car seems otherwise ok, attempt the drive after pointing it down that hill.

A whole lot of "if's" involved on this... and if this was a few years ago (I had more funds, resources then), I'd never consider any of this. I'm laughing just thinking about all this.

Bummer, without decent resources it's tough to do stuff like that. If you're even considering it though, you're still standing. Maybe you could raise some funds by parting out the SEL. Good luck.

Join AAA or another emergency road service that covers 100 mile tows. I got one at a place called Better World. They don't care which car it is, only that the "owner" is there and that it really is broken down. They might have a problem if the car is not currently licensed.

My coverage gives me up to 4 calls - jumps, tires, tows (up to 100 miles or $250) and cost less than $100 a year. It takes 3-4 days to go into effect, but it might be worth it. Get a friend to drive you there or take public trans and ride back in the tow truck.

The guy I just bought my car from used his AAA to have my car towed 50 miles because the plates were expired. Nice guy.

FWIW, I just bought my wife a "creampuff" 300SD that was 160 miles away. I had pictures and descriptions, but I knew I'd find something wrong. I did, but it wasn't major. The point is, it will be worse than you think, but may still be OK.

Good luck!

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer

Thanks for the ideas, guys.

Pete. I was wondering about getting that sleeve out. The article I read mentioned making a tool to compress the cover, and mentioned replacing the sleeve but didn't say how.

The 380... well, it had been wrecked at some point, and the windshield isn't perfect, and I only have the valet key, which means more money at the dealer. It isn't registered either. I just went out and looked at the car, and under the dashmat, the black pad is perfect. I had been trying to sell the whole car, for dirt cheap, with no luck. Perhaps you are right about parting it.


tenknots, The emergency road service is a great idea, and one I hadn't thought of. I could have used that a few times in the last few years.

Wow, a 160 mile one way drive to inspect a car. That is devotion.

If you are really interested, I could describe the "tool" I made in more detail, the critical component being a filed washer BUT I would see if I could take the piston out (noting it's orientation first)and see if there is a groove worn in it. Maybe file it and reinsert and check for free movement. Check car over (check engine for excessive blowby) and see if you get it home

Don't know how to make a like to a past thread, but I bumped mine on replacing a B2. Frankly, it still isn't running quite right, won't go into third until it warms up a little, and flares a little at part throttle, could be something to do with the little c shaped metal pieces that seem like a spring worn down the side until it totally broke apart...

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'84 300SD veg-oil bliss
'83 300SD veg-oil beater