Euro w123 300d Trans slipping shocking bad in 2nd 722.405

[300d 4 ME]

After a grueling 60 mile trip today. I brought home a 85 w123.130 Euro spec 300d Non turbo sedan (Auto) 722.405 trans.

She was a great deal, due to the trans not going past 2nd gear.

So here is what happens...

It goes into all selector positions fine. Low gear feels normal, now the 1-2 shift is harsh and flary- but livable.

After getting to around 15mph the engine roars, and it feels like it drops into neutral. Just nothing but revving. Have to slow down enough to catch 1st gear, before it starts acting like a trans again.

I've checked, the fluid level-is perfect. P/O said it and filter was changed after this all happened. I know this doesn't help with the detective work! Claimed it wasn't burnt- but take it as you will!

and played around with the bowden cabe- no change. Was/is adjusted perfect.

This has no 3/2 valves on the valve cover..


Left the kickdown switch, and vac to modulator off. Didn't help...

Also tested vacuum at near 15g for the vcv going to trans. Same for vac holding- everything is just fine.
Cranked the modulator in 4 turns clockwise, it held the gear a little bit longer, but still the same thing happens..

Didn't see a point into hooking up gages to adjust the modulator(since it doesn't go fast enough).

Could it be a piston stuck, or spring broke? Please toss me some suggestions...

Pics to come soon.

[Frank Reiner]

Clutch K1 not applying. Why? Either a valve body fault, failure of the clutch mechanical components, or failure of the clutch apply piston seals.

[300d 4 ME]

Alright, I've been looking at all the threads about K1 issues I could find. Seems a good start is to get the k1 upgrade/ spring MB kit-with piston. Have little hope it will simply solve it, but either way I would do it in a rebuild.

So why not?

[Frank Reiner]

Originally Posted by 300d 4 ME

Alright, I've been looking at all the threads about K1 issues I could find. Seems a good start is to get the k1 upgrade/ spring MB kit-with piston. Have little hope it will simply solve it, but either way I would do it in a rebuild. So why not?

The references in essentially all of the threads on the subject of "K1" are to the K1 accumulator, not to the clutch. The function of the accumulator is to soften the application of the clutch in the interest of comfort. Unless the K1 accumulator piston has disintegrated the fault will be found elsewhere. Installation of a new accumulator kit during rebuild is worthwhile.

[300d 4 ME]

I popped off the pan today, and had a look at the k1 piston assembly in the valve body. I saw nothing broken. To me it looks like the sealing rings have a lot of wear, and are scored with itty bitty pieces of metal. It came out, and went back in with little force. Like the seals aren't doing much.


I saw super fine metallic stuff in the oil, wasn't magnetic-looked like aluminium... Where would you go from here? Start taking the trans out? For what its worth the P/O said it happen all of a sudden. So me thinks it is a hardware fault...

Have a look. Sorry about the large size, don't know what happened...

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[Frank Reiner]

300:

If you are comfortable with the idea of exploring the valve body, that would be the next step. You will be looking for a damaged or stuck valve spool.

Look in the Members List for "Stretch", and find his tutorial on a rebuild of a 722.3. The 722.4 is the junior version of the 722.3, and the valve body steps are the same.

[vwnate1]

I'd suggest replacing those worn out accumulator O-Rings first....

Don't over think it, fix what you find wrong and try again .

[300d 4 ME]

I thought about popping the valve body off while I was in there. Realized I needed to clean up more, maybe lay down some plastic on the counter.

Went ahead and got the k1 piston/ spring kit. I'm sure those old seals are leaking. Highly doubt enough to instantly cause this to happen....

I'm not well versed in AT transmission. Though just about every other area of these old benz. Been lucky I guess.

[nastala]

I've collected a bunch of 722.3 info, take a look through here: https://archive.org/details/mb7223 . The technical overview is good, as well as the official MB manual.

[Junkman]

I had some flaring and found a couple of springs broken. I forgot what springs but they were accessed via the cover on the side of the valve body.

You don't need to drive the car to adjust the governor. Just do it at idle. You will get the same results.

Here's a guide I found while looking around.

https://ln2.sync.com/dl/8dc741e50/98td6ghb-y8q86uri-f6bmabzq-jvwkj4gx

[300d 4 ME]

Yeah further valve body inspection is next. Spent today cleaning up the shed, in prep for "AT surgery"....

Its not so much a flare, as it just lets go of it-at 15mph. It feels like it might be slipping once it gets into second. I really can't tell. Haven't been in a auto w123 in years... Either way it is instant once it goes, I have to almost stop to get it back into 1st, before it tries again.

I can do a gravel burn out in 1st... Very strong.

[300d 4 ME]

Originally Posted by nastala

I've collected a bunch of 722.3 info, take a look through here: https://archive.org/details/mb7223 . The technical overview is good, as well as the official MB manual.

Thanks for the link-collection!

I got the valve body off. On the first look through I've found nothing stuck. Haven't cracked into the ball bearing side yet.

Did see that it has been opened up before. Noticed how the straight headed screws were chewed up, and torqued within a MM of there lives!

Leaning more towards a full rebuild. Found some wee slivers of something in the fluid. Not magnetic...

[300d 4 ME]

Here is a pic of k2, and b1. So the little spring in each of these is supposed to bounce back and forth? I have none of the other stuff it shows on the exploded diagram...

It slides back and forth(you can hear it when moving the valve body).

Found a wee chunk of neon green plastic in one of the ports. Also found the upper and lower body half wasn't really bolted together with the 2 securing bolts. They were completely loose.

Not that it matters when bolted onto the trans.

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[300d 4 ME]

The trans got yanked out 2 months ago, just been waiting... So here are some pics of what I believe caused my issues. It deserves a thread all by it's self.....

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[300d 4 ME]

So for those of you playing the home game. The planetary carrier sheared off the rivets, and ground through that aluminium piece attached to it. Had to file the teeth on the hub to get the discs out.

Amazingly enough, the clutches, plates, brake bands-etc. All look normal, with no hot spots, or bad wear..

Now for the kicker. While during disassembly, I popped of the oil pump(rear side of case).

I was looking at the Ast manual during this. Came off fine, but I noticed something.

IT HAD NO GEARS!!!!!!!!?

Somebody must have had it apart, and left out the gears. I can't believe it!

I drove it around the block like this too. No more than 10mph-but still.

The previous owner said he took it to a garage to see what happened to the trans....

So what would have caused the planetary to just let go? I wonder if all of the fluid in the engine compartment had something to do with all of this..