Oh no, needle bearings found in trans pan

[owner]

I was doing a basic fluid/filter and leaking connector plug service on the 722.6 trans in my OM612 powered MB ML270 (this vehicle is similar weight to my unladen T1N and same running gear), but things took a turn for the worse...

Stuck to the pan magnet were about 10 loose needle roller bearings. Also inside the filter I found metal shavings...

https://drive.google.com/file/d/0ByLwC5UP406xVE05dHJzak9ZOEU/view?usp=sharing - high res version.

Word on the street is that its some kind of thrust bearing that has broken down. The rollers are about 1.5mm diameter and about 4mm long. I dropped the valve body and found about 8 more rollers stuck on the magnetic speed sensors.

The fluid (Genuine 236.10) is about 50k km old, it was fairly black. The trans has done 285k km. This has happened within the last 50k. The previous full 13l fluid flush/change I did when I got the car 50k ago, fluid was brown and no metal in pan. History beyond that is unknown, but these vehicles were sold new with the "sealed for life" BS guarantee. So MB wouldn't have done any trans servicing during the warranty period.

The trans used to make a whining noise on overrun in 2nd gear, but it seems to have gradually stopped doing that noise at some point, I guess there is more play now with the broken down bearing lol.

I can't afford a rebuild, I have a spare trans of unknown condition that I could put in. But I'm thinking I will just run it till it dies, maybe with a drain plug fluid change every time I do the engine oil (this car has no drain plug on the TC (sealed for "life" remember), so you will only get about 3l out of the pan drain plug). Unless someone who knows more about these things says its better to bite the bullet and somehow fix it before it dies?

For now its back on the road with 5l of fresh 236.14 mixed in with the old fluid in the TC, and a new filter.
EDIT: I should add that the trans runs and shifts perfectly. I did have an issue with very occasional (maybe once every few months) limp mode due to trans speed sensors (implausible gear ratio), but that was presumably due to all the roller bearings stuck to the speed sensors.

 

[220629]

Bummer.

It's amazing to me that presumably all the needles have made their out and it is still operating normally.

I have no advice except to do the Google on the internets to see if there is any info out there as to finding a similar condition and just pressing on.

I don't know if additional pan drains will really buy you much for a shaft turning without bearings. It certainly can't hurt though.

My 2006 157,000 mile transmission sounds different, but not terrible as compared to my 2004 303,000 mile. I'm set to drop the pan and change the filter/fluid. Fingers crossed for mine.

Good luck.
vic

 

[Old Crows]

That sound awful!

 

[Midwestdrifter]

Depending on where the thrust bearing is, it may only be loaded in a specific gear. You could go some time before you have major symptoms. With good lubrication, the lack of the thrust bearing isn't immediately fatal in many cases.

Unfortunately the added free play in the stack up may cause damage to whichever housing the bushing resides in. I would say replace the bushing if you have the time, shop, skills. However the damage to the surfaces is likely done, so you will need a few need hard parts.

 

[AdrianD]

What year is it ?

 

[owner]

Its a facelift ml270 year 2002. Supposedly they beefed up some of the transmission internals in 2001, but not enough I guess.

 

[AdrianD]

To me those parts look like they come from a sprag. Especially that trapeze shaped part.

 

[owner]

Yeah that trapeze shaped part caught my eye too, but it seems smaller that the photo I saw of a sprag on that DIY rebuild thread, but its hard to judge sizes in the photos.

My wife has just reported today (she drives the car usually) that it has been going into limp mode a lot this week. So my hand may have been forced early. I will check withe codes with my star diag tomorrow. I guess the fresh fluid may have dislodged some more metal shavings and/or rollers.

If you skip to 14:10 in this video, you can see a thrust bearing that looks like the right size.
https://www.youtube.com/watch?v=M1Wlb9rvXAY

Also shown in this vid at 9:14...
https://www.youtube.com/watch?v=rKkB9n7NWw0

Also at 12:20 there is a much bigger bearing but the rollers look like the right size, damn thats a lot of rollers.

 

[AdrianD]

Yeah, until you hold a sprag or a solenoid in your hand you can't tell their size.

Anyway, if it is going in limp mode, better stop driving it. All the repair shops I talked to recommended a torque converter replacement because debris can get into it and you don't want them in a freshly rebuilt trans.

When you replace it take it apart and tell us what you find.

 

[owner]

I've just finished putting a replacement used trans in. Me and Eric went halves in a writeoff ML270 a few years ago. It had an engine fire (Power steering hose blew off and fluid caught fire) but only the front of the engine and front bodywork is burnt. So I took the trans out of that.

Was a bit of a saga getting it swapped over. Well actually the swap went reasonably smoothly, considering there is also a transfer case the size/weight of the entire trans bolted onto the back of the trans - so its like doing 2x trans swaps in one. But when I went to start it afterwars it gave the dreaded "start error". That error took a whole day to fix. For some reason the DAS (ML version of the SKREEM) had decided to disable the keys for no reason, AND gave some BS error code that led us on a wild goose chase checking everything but the keys.

Anyway, the new trans had good honest well used brown fluid in it, and no odd metal or otherwise particles in the fluid/filter, or speed sensors etc. It shifts really well, I'm really happy with it. The wife even commented on how well it drives now!

Next week me and Eric will tear down my old trans and see what carnage we find.

 

[AdrianD]

woot, I love carnage pics !

 

[owner]

Eric and I tore down my dead trans today, and we also tore down a spare one to cannibalise for parts, to make one good one. Mine has the bearings in pan issue, and the spare one has tons of clutch and plate material in the fluid/pan/filter/everywhere.

Now, lets have a quick game of spot the difference...
My B1 clutch assembly:

Spare B1 clutch assembly:

(HINT: read the thread title)
This B1 clutch assembly is the first thing you remove, it is attached to the back of the bellhousing. The thrust bearing you can see is the No1 thrust bearing. You can see that on mine that every single one of the rollers has fallen out of the bearing cage. According to the manual this bearing is not a replaceable part, you have to replace the whole B1 cage etc.

Now look at the K1 clutch assembly, this K1 bearing surface mates with the No1 thrust bearing...
Mine:

Spare:

As you can see mine is very badly worn. The good spare one has a half mm raised section that the bearing rolls on. Mine this raised section has been scored/ground down flush with a groove cut in as well. Gah.

So we took the B1 (whole thing incl bellhousing) and K1 from the spare one, and put it in mine. The insides of the spare one looked really nice and clean, with plenty of meat on the B1 and K1 clutches that we looked at, the thicknesses measured as-new...

My guess is that its the torque converter clutch that has broken down in the spare one. The rest of the trans' guts looked new. Even my trans, except for the missing bearings and that surface looked brand new inside, with as-new B1 and K1 clutches. Also there was zero damage to any of the gears etc. There looks to be a clear path for the rollers to drop straight out of the B1 clutch pack and through the speed sensor holes and straight out of harms way, luckily.

So now we have one good spare trans ready to go.

 

[AdrianD]

Woot. I've never read about failures there but good to know and good to have a spare trans ready.
Seems like the one which failed with clutch material was just like my first trans+converter replacement. Ran 600 miles with fresh fluid then it started to clog the filter and all of the clutches showed normal wear.

 

[220629]

I'm not very familiar with automatic transmissions other than operating them.
That said, I have been around other power transmission equipment.

That thrust bearing appears to be pretty skimpy to me. That would hint that it may be in place to accept an occasional bump, and not really intended to be under constant load.

Accepting that premise, are there any unusual conditions or possibly other worn/out of spec parts which could cause that bearing to be under constant load? The failed part(s) in equipment can be a casualty rather than the root cause of the problem.

It is fortunate that you mention the broken bits can mostly fall free. That means that the condition may result in louder noises as a warning during operation and is not as likely to just explode. I have no data.

Thanks for taking the time to write up what you found, and of course the pictures.

vic

 

[Old Crows]

Oh my! Why are we drawn to tranny porn?

 

[owner]

Yea good point Vic, I was thinking about that myself, all we have done is replace a broken bearing, we haven't fixed what caused it. The light loading on that bearing you mention is also backed up by the fact that you can't just replace that bearing, you have to buy a whole new B1 cage because the bearing is integrated.

So I think we might put the B1 and K1 back into its original "spare" trans, and use the TC off of mine. Because that spare trans looked like the issue was the TC clutches breaking down, the guts of the trans looked perfect as you can see in the photos.

 

[Midwestdrifter]

It is possible that the bearing was damaged by some transient condition. Possibly during assembly? It would take some time for minor damage to accumulate. At some point the needles start to slide instead of roll, then it goes downhill fast.

Was the bearings cage metal or plastic? Plastic cages can be more easily damaged by assembly error, overheating, or chemical exposure. Once the cage cracks its just a matter of time.

 

[glasseye]

Oh my! Why are we drawn to tranny porn?

Because superb photography.

Kudos, owner.

 

[owner]

The bearing cage is metal, and is captive somehow in the B1 cage. My trans did used to make an odd noise on overrun in 2nd gear. My guess is that the noise stopped when that bearing broke down. So it lends credibility to the theory that there was some kind of loading on that bearing that shouldn't have been there.

 

[coolestmanalive]

I had the exact same failure.

Exactly the same.


Doesnt it piss you off that those bearings are non-servicable?

replace the whole god damn stator just because that 1 single, of the 2, bearings failed?



My biggest issue is that I cant find the correct stator anywhere. ALL applications I can find are either:

a) Mercedes 1996+ 140 272 22 24, meant to house 3 or 4 single or double sided frictions
b) Chrylser 2004+ 140 272 22 24, meant to house 3 single sided friction.

Example:

http://www.cctransmissionparts.com/downloads/catalog/09_Mercedes.pdf (page 885)

My original stator (140 272 22 24) houses 5x single sided frictions.


I literally have yet to find a single reference, anywhere online, to a 140 272 22 24, 722.6 stator meant to house 5 sets of frictions.


FYI, the difference is the gap between the teeth of the stator and the snap ring. Bigger gap? smaller number of frictions.... smaller gap? larger number of frictions.

Chrysler application (3 sets of frictions) has a 0.410" inch gap. My stator uses ~0.25" gap and 5x