Gearbox for E91 BMW 320d Touring Sport Plus - Help

[Dr Ing]

Hi everyone started this thread because I know there will be some lovers and owners of the exact same vehicle in here somewhere and some of you may have some experience or good advice for what I’m struggling with.

As advised by my mechanic, I am now sourcing a new gear box for my 320d 2011 BMW Touring Sport Plus - I have gathered the following data so far:

I still have the car as I need it to drive and now with lockdown things have got more problematic (I have mastered moving from 1-3rd for the time being) however in the meantime, I am going to try and source the part, get it first and then hope my mechanic can put it in when the wider situation permits.

3 Series E91 LCI 2007-2012 N47 - this is the start stop version.

I have the Chasis No and have checked this on ‘realoem’ and other similar code sites

Now where this gets interesting and to be honest where all of my basic knowledge hits the wall is...

The mechanic and breakers (those I contacted have a few in stock) have warned me to be sure that I am getting the right gearbox as there are longer gearboxes for the ED version.

From the codes and websites I have looked at I think I am looking for a:

ZF GS6-45DZ

...however there is one suggested with the added extension code HAK (which seems to be for the ED model)

If anyone knows anything more or if I completely barking (mad) up the wrong tree please let me know...I would really appreciate your help.

It’s very confusing when you are staring at all the info with my very limited knowledge.

I know taking the existing gearbox out of the car and then looking at the codes on it would be the easiest way but I am trying to find a work around in difficult times.

Appreciate anyone investing some thinking time for me in this...

Edited by Dr Ing on Saturday 25th July 19:28

[rallycross]

Have your looked at real oem for the part number just enter the last 7 digits of your chassis number.

https://www.realoem.com/bmw/enUS/select

Try these for a used gearbox


01279 417755 Or

01952 461462 Or

[phone]

[Dr Ing]

rallycross said:

Have your looked at real oem for the part number just enter the last 7 digits of your chassis number?

Yes I have and when I did, if I am reading the information correctly I think it is telling me that I need the ZFGS6 - 45DZ ‘HAK’ (HAK appears to be for my ED version) however I am not sure if I am reading this correctly or understanding the information listed correctly.

Many thanks for the contacts...

[Dr Ing]

Just bumping this up and hoping that someone else out there might have a bit more knowledge to share on this...I haven’t quite solved it yet....

Edited by Dr Ing on Wednesday 13th May 20:17

[Dr Ing]

It also got MOVED which I completely understand...
This is where I perhaps should have had it to start with...
I don’t post or start threads much so I’m not in the way of the best process for these things!

[BFleming]

Dr Ing said:

Just bumping this up and hoping that someone else out there might have a bit more knowledge to share on this...I haven’t quite solved it yet....

Where do I start! My old 2010 320d ed had the GS6 45DZ box from the factory, and when you start reading up on them, you hear how chocolate they are (particularly reverse gear). Parts are unobtainable, replacement boxes are expensive secondhand, and there's no guarantee per se on how long they will last. So the previous owner of my car fitted a GS6 37DZ box. Physically a straight swap, complete with the start-stop neutral position sensor on top of the gearbox, but different ratios. I did a lot of digging at the time about why my gearshift indicator didn't work, cruise didn't work, and I had a hidden DDE (diesel ECU) code saying 'Final Drive Ratio Implausible'. The ed had a final drive ratio of 1:2,79, and the new box & it's shorter ratios meant I would have had to fit a differential of 1:2.3 or so balance things up - which doesn't exist. The regular 320d (non-ed) with the GS6 45DZ has a final drive ratio of 1:3.15. But where it gets interesting (if such things interest you) is that the GS6 45DZ coupled with the 1:3.15 diff ratio has identical (2% deviation max) driving ratios to the older GS6 37DZ coupled with the 1:2.56 differential. So I ended up fitting a full-fat 320d ECU to my ed and changing the rear diff to 1:2.56. And hey presto, all my problems were solved. It's easier for you though as you already have a full fat 320d.
So in summary, replace your gearbox with another GS6 45DZ, like for like replacement, but same potential box issues in the future.
Or
Replace your existing gearbox with a GS6 37DZ and a 1:2.56 differential, stronger gearbox, but same driving experience/overall ratios as you've always had.

Just for reference, the gear ratios are as follows:
GS6 45DZ:
1st - 4.11
2nd - 2.248
3rd - 1.403
4th - 1
5th - 0.802
6th: 0.659
Final drive - 1:3.15 (ed - 2.79)

GS6 37DZ
1st - 5.14
2nd - 2.83
3rd - 1.804
4th - 1.257
5th - 1
6th: 0.831
Final Drive - 1:2.56

Compare 5th in both cars to prove my point about the overall ratios being the same (well, very very close)...
GS6 45DZ: 0.802 x 3.15 = 2.52
GS6 37DZ: 1 x 2.56 = 2.56 (difference is 1.4%, which the car's ECU etc deems 'near enough').


My old 320d is still running happily on 160,000 miles, 3 years since I changed the diff to correct the issues I had. The diff cost me £50, and GS6 37DZ boxes are a lot cheaper than the GS6 45DZ. Although I've just had a look, and GS6 45DZ boxes are more plentiful on ebay now than 3 years ago.

Finally, contrary to what your mechanic has said, there is no difference between any of the ratios in any of the GS6 45DZ boxes. They're all the same whether from a ed or regular 320d.



I hope this helps.

Edited by BFleming on Wednesday 13th May 20:57

[Dr Ing]

Wow thanks so much for this. So I certainly wasn’t wrong in this requiring a little more investigation but you have provided some fantastic information that is likely way to be way beyond whatever I’ll be able to understand. Thank you so much for taking the time to post all that!

Overtime though and when I’m working with people who do, I can’t wait to start talking about differentials and all that!

So to help clarify for the uneducated like myself:

If I can source the GS6-45DZ gearbox go ahead and get it without worrying about the additional end codes like H5H or HAK.

Also if I can source a GS6-35DZ that also will work if attention is paid to setting the correct differentials.

Please correct me if I’m wrong...

Edited by Dr Ing on Thursday 14th May 12:06

[BFleming]

Dr Ing said:

If I can source the GS6-45DZ gearbox go ahead and get it without worrying about the additional end codes like H5H or HAK.

Also if I can source a GS6-35DZ that also will work if attention is paid to setting the correct differentials.

You've got it (apart from the 35DZ reference, it should be 37DZ). In my experience the end codes don't matter, but I don't know 100% what they do mean. I suspect different build years with minor revisions by ZF, as older ones are listed in RealOEM as superseded by Hxx.

[Dr Ing]

Ah yes GS6-37DZ noted - many, many thanks for this - this has helped me move forward with this

[Dr Ing]

Dr Ing said:

Ah yes GS6-37DZ noted - many, many thanks for this - this has helped me move forward with this

I have found a breakers yard close enough to me (less than 40 min drive) who have a GS6 37DZ in stock. He said this is from a 1 Series - so do we think this will definitely work. Only going to cost me £200 - I hope my mechanic has your knowledge and does not give up when the codes don't match...

I know I run the risk of buying another gearbox nearing the end of its life but worth the risk I think...

[BFleming]

It'll fit as long as it has the neutral position sensor on top.
Also you'll need the diff to suit (1:2.56).

[Dr Ing]

Is this something I need to check at / with or before I go to the breakers?

How do I do that?

[BFleming]

Dr Ing said:

Is this something I need to check at / with or before I go to the breakers?

How do I do that?

The neutral position sensor? It should be fairly obvious on any pictures you see...

[Dr Ing]

BFleming said:

Also you'll need the diff to suit (1:2.56).

You are brilliant my friend - thanks so much for the picture - I am going to be able to fit this myself by the time you are finished with me!

Can I just ask about the differential setting required you have stated it needs to suit...

Again, is this something that I need to check is possible before purchasing the part or just something the mechanic needs to know to do with the part?

If I need to check - how is that done? Is it something I can do myself or perhaps the breakers can do for me before I make the trip? What am I looking for?

I appreciate your time and patience with me - the info is invaluable.

I have been quoted £200 for the part - does this sound reasonable?

[rallycross]

Bmw have loads of different diff ratios across auto and Manuals for same model I’d suggest get the gearbox fitted and see how it feels with your current diff then live with it...

Only if you are unlucky it will be too low geared and you will find motorway cruising is annoying due to too high revs But you might find it’s fine as is.

Changing a diff is going to add another few hundred £££ and it’s a horrible job on older car plus getting the right diff can be tricky.

[BFleming]

rallycross said:

Bmw have loads of different diff ratios across auto and Manuals for same model I’d suggest get the gearbox fitted and see how it feels with your current diff then live with it...

It'll cause issues if it's not the correct diff. In short, the gearbox ratios are pre-programmed to the engine ECU (DDE in this case). If the car is seeing wheel speed and engine revs that it doesn't expect, it'll cut power. Cruise won't work, the gearshift indicator won't work. Been there, unfortunately.
Just to repeat, use the original 1:3.15 diff if you stick with a GS6 45DZ (standard 2011 fitment) gearbox, or a 1:2.56 diff if you switch to a GS6 37DZ box.
Price-wise, I'd expect a 1:2.56 diff to cost £30-£100 (I paid £60 I think for a nice dry good condition diff, and a local garage fitted it for £100. I changed the oil in there before I gave it to them to fit). The 1:2.56 differentials are the most common E90 differentials to be found. The GS6 37DZ boxes are plentiful, so £200 sounds right.
I'd put a new clutch in there too while I was at it, and your mechanic might recommend the Dual Mass Flywheel too. I can't comment though, that's up to you & your mechanic to decide.

The differentials have pre-set ratios, and will be labelled up as such. They're not adjustable in that sense. You have a 1:3.15 currently. The 1:2.56 will have a sticker on the top, looking like this:


In a very simplistic diagram, this is what the hardware of your BMW looks like. Rear wheel drive, engine & gearbox at the front, driveshaft connected between the gearbox and the rear differential. The things that vary the ratio of engine speed to the rear wheels are the gearbox (with its 6 forward gears) and the differential (one fixed ratio)...


So if you fundamentally change the set of ratios in the gearbox (by fitting a new (different to original) gearbox), the car needs a corresponding ratio change at the rear axle - so the rear diff needs a change too. Modern diesel BMW's are really fussy about this.

Pre-2009 manual diesel 4 cylinder E90's had the GS6 37DZ box and a 1:2.56 diff.
Post 2009 manual diesel 4 cylinder E90's had the GS6 45DZ box and a 1:3.15 diff.

Both box & diff combinations gave the same overall ratios as each other.

Edited by BFleming on Friday 15th May 14:16

[Touring442]

The later boxes are complete st, another 'improvement'.

£700 for a used 45 that might go wrong again versus £200 for one that probably won't.

A diff swap will take about an hour on the ramp with air tools, nice easy job. A used diff won't be worth a lot as they almost never fail. A 7566225 or 7566226 is the one you want. Fitted to lots of E90 and 1 Series stuff.

50 quid:

https://www.ebay.co.uk/itm/BMW-1-3-SERIES-E81-E87-...6gAAOSwsFZeRrx2&enc=AQAEAAACYIQvEcHUrT7nmUC3yY5qbPyaBN1nJEDYW8MyypsJPgXKWvGWBPIgzGbX1fJ04aU6u6dOv8wXEOXKaw4bt7XKt%2BSbOpovKNyhKGzU%2FKA6%2B%2F3aBlYwAVPprDOql3StwGjp0sWAxgmiGg39IfUDlQ5Ntsxper1L1KiQd0wEW0m1MKV2ZVPvxRNQXfOuOWzLHtOWCvcbgAS5abHYl4VZT9AlZzGnHJ7tuWiWgcZ9JKCrMmTJOyC%2BB%2FLtoVNb9bX%2BIQU5CL50cYTwk5eyYwDwnBwmh9Q1l1ZdNwJltmMkgfeaM7T0Hh%2FPShOAx%2FP4O2%2BIekrqplTxS9GjQ3TNSRfkLrCKQds0FPiPOoMzLB3esQ8gVSsuutm%2BCLBTXbm%2FOSh67NxeTRFGqZhH7Ot2tCFFEh04clMwSM8YwYDQk1K0RdmBTqclc3fN7eDVHeGoMBPrrxadvqGqbUaCVO5RPI8CTKSCDCOaYbwqxsVb%2FRH%2BlKLoymdhhn4bZA8sx9Npo14dLXsgfQwasYkyMthyThJrH7mwQ0ICJok3aX4ufO%2BAlLhfGo9rCRQMEtnNglJ%2FjQoL9y%2F3a27oqIPofxuJ0ireCJ6XK2%2FNnvWCK%2F3%2Bcdk%2FjCtr87R9pTD352shE16eO3PyHjrGkW2IBtN%2Fm2WEil5EyvkbM4IOn%2F5bLcFE7O8NNwLKUG3veQrrUwJHPtPbTT5eE15L16bgagPvv%2FeUd68MdYyBDZuvwuE0DxgG7O%2BcozPOAlpAz3GI0Mz5Pn%2Fw5xAluG8VwR5AzfHf3kLcLuw%2F0G7Aqth7BYLQHOrrqy%2FWD433p41o&checksum=1538326884912d24929ee8df4959aafa91feec25a34c

[BFleming]

7566226 is indeed what I fitted.

[Dr Ing]

Just a little final update gentlemen to let you know where this all went in the end.

I managed to locate a second hand GS6-45DZ (HAK) without too many miles on the clock and picked it up at a very good price. It was shipped to me quickly - I have to be fair and say the company were great to deal with and I would recommend their service.

My own mechanic (after inspection) advised that the clutch and fly-wheel needed replaced - which we also did.

The gearbox and car are now working like a dream and I am back in love with my wee car.

All in: for parts and labour the total price was well under what I had envisaged and well below the deposit on some of the new cars I had been considering buying!

I am now thinking of some little upgrades to the car inside and out that might give it another little lift.

Many thanks for all your help and advice on this!

I just did not have the confidence in the end to be too ambitious with this gearbox change but I have learned what a rear differential is and I am looking forward to building on this knowledge! Hopefully not with this particular car or gearbox though...

Edited by Dr Ing on Wednesday 1st July 01:27

[Dr Ing]

So I now have a few longer journeys under the belt now and the car is truly driving like a dream.

Working on a few aesthetic exterior and interior upgrades now on another thread so if you have any other expertise or advice you want to continue to pass on my way there I’d much appreciate it...

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Edited by Dr Ing on Saturday 25th July 19:27