Didn't see this one coming. Reversed out of my driveway this morning, shifted into Drive and POOF, nothing but revs/slippage and a tiny bit of forward momentum.

Coasted up the street a bit, shifted down to S and revved it a bit, seemed to catch 2nd gear but still with huge slippage.

Crawled around the block to let engine warm up so I could check fluid.

Nothing showing on dipstick (checked on level ground at idle). Put in 1 liter (about a quart). (Now the dipstick shows way overfull.)

Symptoms now:

If I come to a full stop, or close to it, I lose drive.

When I try to start off again I get massive slippage but slowly gains speed to where it shifts into 2nd with massive shaking. Then drives normally through 3 and 4 and if I keep driving, is fine.

IF I let it rev really high when starting out from a full stop, it slams really hard into 1st and then shifts normally otherwise.

The ATF loss is sudden. I checked it last Saturday before I set out down to northern NY.

I am at work, did some quick searches but this symptoms profile doesn't seem to come up, not yet anyway.

Will see if I can do a fluid change tomorrow (local stat holiday) but weather has been uncooperative and I work outside....

Tks

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

If it's a 722.315 trans, sounds like the B2 piston is binding. You'll need to get (new or used) an updated piston and the updated nylon bushing to replace the aluminum bushing.
Hopefully the case is not gouged which will lead to a bigger issue.

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1983 123.133 California
- GreaseCar Veg System

I can help you out tomorrow, need fluid and filter? I have it (at least for the W126 SD and 240D). You print the directions out...if you want me to bring the tow dolly for a ride back to Scott's I can do that too.

Thanks, you've got Gmail.

From what I remember from years of reading about other peoples' woes, the B2 is JUST do-able with the transmission in place, dropped off the mount.

For normal-sized hands (not mine for sure).

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Check the level again. I doubt 1 qt would go from none showing to over-fill. When the fluid is low, splashing can cause it to appear too high on the stick, at least my experience w/ my Chrysler trannys. In those, there is no risk from over-filling since it just spills out the overflow. Some here say that over-filling can hurt a M-B tranny.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

The dipstick shows way overfull when the engine isn't running. It'll be like a good four inches or so above the full mark.
Fluid is checked with the transmission at operating temperature, which is impossible to do when it won't drive, so with the engine running it'll show low on the dipstick. A warm engine does not mean a warm transmission.

Anyway, if and when you carefully get the car up to speed and 3rd and 4th seem to work fine and you still have reverse gear, then your symptoms seem to point at B2 piston failure, which thankfully is not the end of the world. They tend to fail without prior warning, so it's usually instant failure.

There are a lot of very detailed how-to's to be found online when you search for "B2 piston w123" on Google. I'm not going to post any links here, because I don't know if I'm allowed to, but it should be easy to find.

Good luck!

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

To clarify:

I checked the ATF dipstick:

1. When the symptoms started (car not warmed up). Level on dipstick was a bit below the full mark.

2. When the engine had reached operating temperature. Nothing showing on dipstick.

3. After adding a litre of ATF then driving (as best as I could) for about 10 minutes. Level showed way up dipstick beyond normal.

In reading about the B2 failure I have now seen that it can be associated with a fluid leak. I was not aware of that before.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

A liter of ATF to fill up is quite a lot. Between low and full on that dipstick is about 400 something mililiters, so slightly less then half a quart... A quart is roughly a liter, so slightly less than half a liter.

Now I'm sure you probably know how to read those dipsticks properly, but just in case:

1) Have engine idling, transmission in Park
2) Car on level ground
3) Pull dipstick out
4) Wipe off with your clean fingers. Don't use a rag or paper towel, lint can mess up the valvebody in the transmission
5) Put back all the way, pull back out immediately and read level right away

Either way, symptoms are classic B2 piston failure, so I guess that should be the first place to look at. When you work on the transmission, keep in mind to work super clean. A piece of lint, a little grain of dirt, a bug accidentally landing and getting stuck in the transmission can all mess it up...

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)

If you continue to drive / rev the engine to engage, you will damage a possibly reparable in the car transmission.

If you didn't see anything on the ground before step 2 of your post 7, I call that a miss read.

If it is the B2 Piston on a W123 there is very little room to get at the Piston and to pull out the seal and bushing.

When I did it I did as others did and had to remove the Drive Shaft on the Trans End the Support Plate and shove the tail of the Transmission towards the left side.

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84 300D, 82 Volvo 244Gl Diesel

These appear to be the part numbers ('85 300d Federal):

B2 piston: 1072700432

Big nylon bushing: 1262770850

Smaller sealing ring: 1402770455

Thrust pin: 1262779275 (if req)

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Don't forget the sealing o ring.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

I understood that was the third item in the list (the 140 part number). I got that from the Atlanta dealer website.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I purchased from the dealer they supplied a Teflon o ring but I had to wait 10 days it came from Germany. Once I had it I had it matched up with a viton o ring. I was thinking if that large diameter small rim o ring was damaged when I installed it I would have to wait another 10 days but this time without a running car. The one I removed came out in 2 pieces. With luck I had no issues with my installation. Both cost the same C $8.45.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

The stone cold level on the dipstick is about 5mm below the cold mark. If you read it that low, it was normal.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)