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Hi folks,

This might be useful for some.

So, this was on my To-do list for quite some time now and finally had a time and a place where to do it myself.

At first, I wanted to find a good gearbox specialist shop, but since I live in NI I had to go to  Scotland or Ireland. I decided that I will do it myself as I read mixed reviews regarding a transmission oil change.

After researching I decided to go for a metal oil pan instead of a standard plastic one.

 

Info on my car:  2005/03 535d sport current mileage 213400 

 

Issues that I had was while being stopped at the traffic lights and the engine is warm if I step on the accelerator as soon as I release the brakes two out of three times the RPMs would increase, 

nothing would happen for about a second and then when the torque converter would engage it would shoot off. another issue where while driving at constant speed, for example, anything between 40 mph an 80 mph the rpm gauge would fluctuate....  exactly as it is in this video here although if I change it to DS mode(semi-sport) the RPMs would fluctuate no matter how fast I would drive. I thought its the torque converter on its way out, but it wasn't the case, at least in not this instance...

 

Anyway, I found a good deal on eBay, https://www.ebay.co.uk/itm/122680285353  (although you can search and buy the parts separately, it doesn't have to be from this seller) UPS delivered it in three days.

 

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I checked the temperature, it was too hot to do anything so I let the car cool down a bit.

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Had enough time to go over the service_information manual <----MUST READ TWICE!!!!!! one more time

 

The old plastic sump

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New metallic sump on the right

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Old oil sump out 

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Not too much metallic deposits on the magnets, it's a good sign

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The oil itself, it looked like if somebody hasn't changed the engine oil in their petrol car for a good while... it didn't smell like it was burnt or anything

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Mechatronics unit in its glory

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and the important bit... 

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Those 4 seals in the middle of a gearbox, they need changing, but you can't change them without removing the mechatronics unit first.

I suppose in all those threads about fluctuating rpms at a constant speed, almost all the time they are fixed by getting and installing a refurbished torque converter and that ''this is the only way'' might not be true!!!  Maybe yes, but whenever I changed all the seals myself, the hard ''take off'' and ''fluctuating RPMs'' disappeared. so, I am guessing, if somebody changed their gearbox oil ''with all the seals'' they are the most likely culprit as it hasn't been done properly. Take a look at the difference yourself!!!!!!!

 

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the black seal(second longest from four of them) comparing to a brand new seal, you can see that it has shrunk noticeably,  it was the same for the longest seal as well.

I suppose they don't make enough of a tight seal to make/hold a required oil pressure, that's why rpms fluctuate..

 

Someone at the BMW parts department has messed up, as it didn't fit due to a small plastic notch on the other side of a plastic, see the difference in an image. I changed just the rubber bits as the old plastic case was still ok.

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New separate oil filter installed

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All tightened according to the manual listed above

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All done and change the engine oil while at it. The red bolt is a magnetic sump plug, will see if there is any metallic bits in the egine oil, next time its needs changing, looks fancy as well 

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Job done. I reset the oil adjustment and also reset the adaptations(not the factory adaptations for the pressure plates)  using ista and following the service information sheet to the point.  Total cost including all the extra tools(torque wrench and a ''large syringe'' ) was about £280. Time wise better to do it over the weekend in a warm garage. There will be plenty of parts to be cleaned and put back together. It can be done alone. 

It worked for me! The gearbox is still learning my driving style, but it already feels like a brand new gearbox. Well worth doing and no need for a new/refurbished torque converter.

I hope this helps somebody.

 

Feel free to ask if you have any questions.

 

 

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Interesting you did the bridge seals. The transmission specialist in Scotland doesn't replace them unless you ask them too and that's only after they mock you for reading the Internet, am I not right @RightHandGoose?

 

The bridge seals as you point out are a weak point. The leak oil, pressure drops and as a result clutches slip, gearbox needs refurbed.

 

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27 minutes ago, 535i Andrew said:

Interesting you did the bridge seals. The transmission specialist in Scotland doesn't replace them unless you ask them too and that's only after they mock you for reading the Internet, am I not right @RightHandGoose?

 

The bridge seals as you point out are a weak point. The leak oil, pressure drops and as a result clutches slip, gearbox needs refurbed.

 

Exactly that! They are hard to get to... It's just easier to leave them, but it wouldn't be any good as the problem will still be there after the gearbox learn your driving style. I suppose using a torque wrench on extra ten bolts are a bit too much hustle ...

For me not changing those bridge seals would be the same as changing the whole clutch on a manual gearbox, but leaving the old thrust bearing in...

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Great write up, many thanks. It's a job I want to do on my own auto box, but lacking a lift is my problem. I don't suppose you've a gearbox specialist recommendation in Dublin by any chance?

Regarding the plastic notch mis-match, was there some mating piece under the notch on the upper gearbox that prevented the new piece from sitting in place? As it looks like the corresponding surface on the mechatronics box is flat (for the rubber seals) and wouldn't cause an issue.

 

Keliuss

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First thank you for the excellent write-up.

 

There are a couple of points I'd like to make (and I do speak from experience, I've done a couple of gearbox oil changes and replaced the TC on my ZF6HP26).

 

The people who do 6HP26 gearbox tuning are very clear that you should never reset the gearbox learned adaptations unless you actually rebuild the gearbox. You should reset the oil adaptations but not the learned adaptations. I did reset all mine and despite following the full, epic, re-train process my gearbox got it wrong and developed a really nasty change between a couple of gears. I reset it again and drove normally and that did sort it out.

 

The rubber seals between the mechantronics and the main gearbox usually only fail in hot countries but I agree in the merit of changing them when the sump is off.

 

You might find you have fixed your problems but unfortunately it might be short-lived. An oil change fixed my apparent TC problem for about 10k miles. Another oil change for a few thousand miles. Fitting a refurbished TC really fixed the problem and feels very different and a lot lot better. Hopefully yours will be OK though.

 

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16 minutes ago, pidgeonpost said:

Bugger. There was me feeling kinda smug and secure after getting my 'box serviced at around 60k 18 months ago, I'll now have to be fretting about bridge seals I guess.... :lol:

 

Lol, I know what you mean

 

There is an argument for doing them and as mentioned above can only be a problem in hot climates.

 

BUT...having suffered a box failure, I can't help but think was it the bridge seals that failed on mine resulting in loss of pressure resulting in cooked clutches? But getting them fixed at 91,000 miles wouldn't have helped as the wear to the clutches was done by then......

 

I'll never know.

Edited by 535i Andrew

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On 04/12/2018 at 10:06, keliuss said:

Great write up, many thanks. It's a job I want to do on my own auto box, but lacking a lift is my problem. I don't suppose you've a gearbox specialist recommendation in Dublin by any chance?

Regarding the plastic notch mis-match, was there some mating piece under the notch on the upper gearbox that prevented the new piece from sitting in place? As it looks like the corresponding surface on the mechatronics box is flat (for the rubber seals) and wouldn't cause an issue.

 

Keliuss

2

Regarding gearbox specialist. .. not too sure, but looks like there are several companies doing gearbox repair.

Regarding the plastic notch... indeed there is a groove on the mating surface on the upper gearbox, so it can be fitted correctly. Luckily for me, the seals on both of them are easily removable so I just swapped the seals/gaskets(the case was ok so I reused the old plastic bit). The part I got from the dealership, it's actually 6HP19/21 with a part No: 0501215783 although on the packaging it was correct part number meant for 6HP26 Gbox. So its a fault from the packaging department.

If anybody orders this adapter, then make sure the numbers on the part itself matches the one you actually ordered or you might have to grind the plastic notch off...

 

On 04/12/2018 at 10:17, 535i Andrew said:

Did you take any precautions taking out the mechatronic unit? Do you need to watch out for static and ground yourself etc. Etc.?

 Well... the manual says, not to touch the contacts unnecessary both on a mechatronic side and the electric plug side so I didn't touch them, that's about it. Just don't put it on a ground itself, will be fine then.

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On ‎04‎/‎12‎/‎2018 at 21:52, pidgeonpost said:

Bugger. There was me feeling kinda smug and secure after getting my 'box serviced at around 60k 18 months ago, I'll now have to be fretting about bridge seals I guess.... :lol:

 

I got my 'box serviced 6 years ago !  it still seems perfectly fine, but I'm keeping my fingers crossed for the next 18 months which is how much longer I'll be keeping it.

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2 hours ago, Tuvoc said:

 

I got my 'box serviced 6 years ago !  it still seems perfectly fine, but I'm keeping my fingers crossed for the next 18 months which is how much longer I'll be keeping it.

I've got no plans to change for the foreseeable future. Box behaves as it should and changes smooth. :)

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5 hours ago, Tuvoc said:

 

I got my 'box serviced 6 years ago !  it still seems perfectly fine, but I'm keeping my fingers crossed for the next 18 months which is how much longer I'll be keeping it.

 

Just out of curiosity, what mileage was on it 6 years ago and what's on it now?

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10 hours ago, 535i Andrew said:

 

Just out of curiosity, what mileage was on it 6 years ago and what's on it now?

 

105k six years ago (almost certainly it's first ever oil change according to the transmission specialist) , 145k miles now. 

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As Andrew said, I had an interesting response when asked for the bridge seals to be done too.. But as it was my money it was done. It is interesting that the only ZF Specialist in Scotland does not even mention this an option.... 

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It was never mentioned to me either. The only extra that was recommended to me was the sleeve or connector, which often leaks as well as the sump.

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13 minutes ago, Tuvoc said:

It was never mentioned to me either. The only extra that was recommended to me was the sleeve or connector, which often leaks as well as the sump.

 

Yes another well known weak point in this box but unlike the bridge seals this one is done by specialists on a regular basis for another £30-£40 but the bridge seals aren't! 

 

The sleeve is an external weep, and nothing worse than a mess on your driveway. The bridge seals are an internal leak which more serious consequences. 

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