W163 ML270 2002 722.6 won't engage any gears!

sonic

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Really enjoyed following this thread, way above my standard of repair.
Well done Blueyes & all those who gave advice.
 

Arudge

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Thanks Steve... it's really not hard, only the will required and a few tools.
I never really understood why garages sent gearboxes out to 'Specialist' transmission firms.. and why repairing them cost considerably more than engine repairs.. non of this is rocket science to be fair.
Even when the transmission internals appear to be part of extraterrestrial anti grav propulsion.. they are not.
Google..YouTube and this forum are your friend.. thanks again

That's a great summery and very true....it isn't rocket science and i'd encourage anybody to give it a go. You don't need the finest Snap On tools or fully equipped workshops, a few basic tools, a few blocks of wood and the enough will to give it a go and you're away.

Just give it a go.

But you have to admire that transmissions design, whoever designed it can't be normal:D:D
 

Evolution

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Time to resurrect... I have a 2005 E320 CDI. Bought it with a shagged radiator and subsequently shagged gearbox.

I replaced with a 722.6 gearbox & TC from a W220 S320 CDI- what a monster! The 211 TC is meant to be big, but the 220 one is enormous.

Ran absolutely faultlessly until the other day, when I put my foot down to overtake a tractor, the revs soared as if I was in neutral, and I nearly became an epitaph in the back of said tractor.

Exactly the same symptoms- select all gears fine, revs out in P and N, limits to 1000rpm in R and D. Strangely, manual selection won't work either.

I also have a weird one, if I leave the car and then restart after a minute, it'll work for roughly 30 secs before losing all drive again.

Just read through all of this and will be pulling the trans at some point. I'm only in Coventry so not far from you at all, assuming you still have said ML!
 

Evolution

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Yep, no issue with level, no external leaks. Symptoms are literally identical to what's happened in this thread.
 

Evolution

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I've got a spare gearbox kicking around already- picked it up yesterday.

I have already drained a sample of fluid- it isn't emulsified, no visible shards of metal in fluid, etc. I'll pull the gearbox sump tomorrow and check the magnet. I'd be very surprised if it was anything mechanical, it has been absolutely flawless... until it just suddenly wasn't.

Also, when you turn it on and off, it does come back. But then the manual gear selection won't work, and you're back to square one. Very odd.

I'll get diagnostics on it as soon as I can. I scanned it very recently and there was one issue to do with a speed sensor. Nothing further.
 

Flyinspanner

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If there was an issue on the electroplate (speed sensor) then maybe that has failed and is not allowing engagement.
 

Evolution

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If there was an issue on the electroplate (speed sensor) then maybe that has failed and is not allowing engagement.

That's kind of my thoughts.

1) no noise/explosions
2) I only replaced the whole shebang less than 3 months ago- TC, gearbox, etc. The TC was in fine fettle, and the fluid that came out of the box was perfect. Really good condition.
3) the car has been absolutely flawless, until it just suddenly wasn't.
4) as soon as you turn it on, it'll allow totally normal operation for less than a minute, then it'll tell you to **** off! I drove it on and off the recovery truck, and into my garage. Fairly sure if there was no oil circulating, then it would just refuse flat to move.

I know it's all speculation, but the common sense in me is telling me that it can't be a physical issue.

Anyhow- popping to the garage today and going to swap out the conductor plates.

I may also swap the solenoids, but unsure.

One thing I do remember- I scanned it recently, because it did a similar thing to the missus. She's no fool, she stopped, turned it off, left it a minute, and it was fine. That was a couple of weeks ago.

The only error code in the whole transmission was weird- Y3/6N3 or something like that. I remember looking it up and it related to either speed or something else. Sorry- this is not my finest hour, I was more dead set on working out which parking sensors had gone at the time.
 

Evolution

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Hmmmmmmm.
 

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Evolution

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Valve body out already, and on the bench. Noticing a lot of crud in it. I'm unsure what the hell was in the sump but it's magnetic... however it doesn't look like shards/swarf, it's just... bits. Like dirt. Very odd.
 

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Evolution

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Well, finally got a few mins spare to drive it, in between all the other work today! Drove all the way through the village and back with no real issues. I can only hope it's all sorted for now..?!
 

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LostKiwi

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Valve body out already, and on the bench. Noticing a lot of crud in it. I'm unsure what the hell was in the sump but it's magnetic... however it doesn't look like shards/swarf, it's just... bits. Like dirt. Very odd.
That looks like friction lining from a clutch pack to me.
 

Evolution

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That looks like friction lining from a clutch pack to me.

Yeah, that's what I was wondering, but if you look at it, it looks like old metal? It clearly isn't fresh swarf. The box was sat around for a LONG time before I used it.

It's just driven 15 miles home. A bit shitty at first but seems to have smoothed out nicely. Probably trying to work through the many gallons of brake cleaner I drowned the solenoids/valve body in.
 

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Evolution

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Well. It's disgraced itself. Shat its pants again. I've had the box out. Checked everything.

1) the oil pump was in fine fettle. No play. Oil pump engagement teeth not broken. So ruled out physical oil pump issues. I put in a known good spare one u I had anyway.
2) the replacement box parts inside had massive amounts of corrosion on them?? I can only assume it sat for a long time; presumably in a lake. That explains the deposits in the sump though. I deconstructed a few of the clutch packs, plenty of life in all the discs and no hotspots on any of the sandwich plates.
3) it's exhibited the same issues between two separate valve bodies and conductor plates.
4) I also changed the stator clutch pack for a known good working item with no corrosion in it.
5) I checked the TCM. Plugs were a little oily but none inside the actual unit. Hosed it with contact cleaner, key it dry, and reinstalled it.
6) fluid level has been checked and is perfect.
7) it worked flawlessly for 8 miles or so. Absolutely flawlessly. Shifts were beautiful, shuffled through all gears no problem.
8) still the same recurrent problem- it'll run fine for a little while before it just blows a whistle on proceedings. It works *exactly* as it should. Then it just kicks you into neutral and bam. Game over. Leave it for 2-3 mins, turn on, it'll drive again... for a minute. Then dead again.
9) at the point that it decides to be a cabbage, or a Russian doll, or anything other than a working gearbox, you can't manually select any gears with the stick. It'll recognise PRND, but it'll limit revs to 1,000rpm in R and D.
10) it's had a new conductor plate put in as well as splitting the box down and checking through as many of the bits as I can.

Bizarre. I'm having fun pulling spare boxes to bits and seeing the differences between them. However, the car is meant to be my daily, and I'm absolutely hosing fuel as my V8 3-Series is taking up the slack. I could have bought a refurbished gearbox with the difference in price running the V8!
 

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