E320 CDI Transmission 722.6 box

skipmandy

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Well my Mercedes (E320 CDI 2002 722.6 transmission150k miles) has transmission issues.
Before we part company, I just wondered whether it is a simple fix or is it terminal (ie not worth the cost against the vehicle price).
Driving home the other evening pulling out on to the dual carriageway and without any warning I had no drive.I turned the ignition off and had drove for about 3 miles then again nothing.I repeated this procedure until I got home.I checked the transmission fluid and it seems OK – clear fluid and no dirt on the dip stick.No apparent leaks under the car or any obvious history of preceding gear box issues - noice or gear shift/stuck problems.
It still has this problem – it will drive but for a short distance – 2/3 miles changing up the gears normally then no drive.

Preliminary research indicates a number of possible causes.
Do gear boxes fail like this or could it be a blocked filter faulty sensor etc.
Any advice most welcome - Amanda
 

a111r

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These boxes don't have a dip stick fitted, so you either had the tool or improvised?

Was the level correct? At either 25C cold or 80C hot, it has to be measured in P with engine running.

You say 'clear fluid', did it have no underlying colour to it?
Correct spec (MB atf 134) when new is cherry red, with use changing to a yellowy-brown and getting darker.

You could check the TCU plug and see if there's evidence of fluid wicking up, which would lower the level and could give TCU errors.

That's what I would do, as a DIY-er.
Next would be a STAR diagnosis, which would be definitive, e.g. electro-plate or TC failure.
 
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whitenemesis

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Sounds like the electroplate is failing. Typically the speed senor gives up. Eventually the box will give up completely.

New plate and atf change usually around £400 at an independent
 

bob6600

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Just a thought, being a 2002 and if a saloon it could be a W211 so could be a valeo radiator issue?
 
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skipmandy

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………your knowledge is amazing thank you ALL for your input.
· I did buy a dip stick.
· The fluid was at the 80 mark after the engine had been running for 20 minutes.
· The colour of the fluid is a darkish straw yellow with no debris on the cloth when I wiped it.
· We live in Brittany France, in the country, and our nearest Merc centre is 30km away so it would be quite a job getting the vehicle there without a trailer – so a diagnostic is not the easiest of things to achieve at the moment.
· It is a W210 estate and has a BEHR radiator
Continuing with the elimination process………
Re the TCU plug – do I have to drain the ATF before accessing its location?
Thanks
 

bob6600

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TCU plug – do I have to drain the ATF before accessing its location?
Thanks

No - here's a picture pinched from BlackC55's 'How to'





Some good information in that thread

https://www.mbclub.co.uk/forums/howto/88450-how-change-automatic-gerbox-oil-flush-722-6-box.html
 

Auto-mobile

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Did you actually check it with the engine running though?
 
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skipmandy

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Yes - I did check with the engine running.

I have already come across my first hurdle! Put the car on the ramps took the protective floor cover off and located the TCU. The side plate which needs to be removed first is the problem the bolt is seized solid - I don't want to strip any thread (used T25 the T30 was far too big) but can you confirm what size star drive you would use and what tips you have on helping it on its way.
Just given it a good spray with WP90, not that will help much, as the bolt is into aluminium!
There was no evidence of leakage around the box.

Many Thanks Amanda
 
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skipmandy

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Hi Bob - eventually I managed to get the plug out. There was a lot of ATF fluid around the plug and the connector. I assume the fluid had been collecting in there as about 150mls of fluid drained from the area. Is this normal or does this confirm that this part is the cause of our gearbox issues. Sorry to keep asking questions but I have had to man up my women skills recently and I just want to make sure I am on the right track. Thanks Amanda.
 

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Trickythemerc

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Hi Bob - eventually I managed to get the plug out. There was a lot of ATF fluid around the plug and the connector. I assume the fluid had been collecting in there as about 150mls of fluid drained from the area. Is this normal or does this confirm that this part is the cause of our gearbox issues. Sorry to keep asking questions but I have had to man up my women skills recently and I just want to make sure I am on the right track. Thanks Amanda.

That looks like the pilot bushing in the box needs changing, not a major job and about £20.00 from the dealer. There is a small bolt in the centre of the bush that needs to be undone, it is captive in the bushing so it will not come out of the bush when you pull it out, if you look at the new bush you will see what I mean. When refitting the bush it only requires very low torque on the bolt, if it shears in the box you are in the doggie doo doo.
 
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skipmandy

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Got the part at the Merc dealers in France..........€11 + contact cleaner - will see if it works tomorrow. Thanks again. Amanda
 

ilunn

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You could check the TCU plug and see if there's evidence of fluid wicking up, which would lower the level and could give TCU errors.
Interesting I have seen this on an old td5 landrover but my question is where does it end up Presuming it then leaks out?.
 
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skipmandy

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Well sad to say after putting the new TCU plug in the problem did not resolve – in fact it now slips after just a short distance.
I had a go and thanks for all of your support – possibly; time for the car to be sold on as the other options, although not beyond my learning curve, are too hard to justify the cost or time. Unless, there may be any other cheapish fixes!
Still have the 709 and the Sprinter so not totally Mercless; plus the trusty emergency Peugeot 405.

Thanks again - Amanda
 

merc85

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Reading back ref post 2, Glycol contamination could be the cause of the failure, in which case a New Rad and Box would be required.
 

bob6600

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Reading back ref post 2, Glycol contamination could be the cause of the failure, in which case a New Rad and Box would be required.

Post #10 it's a W210 so shouldn't be an issue
 

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