Z4MR Transmission internal parts, where to source?

[Ascanio]

My gearbox is open on the floor of the shop.
Need to replace the synchro for the 2nd gear and get a seal kit.
Anybody know where to source the parts?

Tranny part number: 23007837983 (GS6-37BZ-TJEE), which appears to be ZF, but have seen forum posts stating it’s Getrag, which has been acquired by Magna, which posted fake phone numbers for their US HQ ).

Having a hard time finding the spares….

[maupineda]

Z’s use ZF Trannys

[Ascanio]

Originally Posted by maupineda

Z’s use ZF Trannys

From what I read around discussions is a bit of both ZF and Getrag depending on trim and model year, but I’m just sourcing from forums

[Ascanio]

In any case it seems impossible to source tranny parts, BMW distributes them only as whole packages, and ZF USA has proven completely unhelpful, to the point of referring me to distributors who no longer distribute them!

[grannyknot]

I`ve spent a lot of time myself hunting for a rebuild kit, have never found one.
https://metricmechanic.com/
is one of the few companies that rebuild the 420G, they may sell you some parts.
You could also try, https://diffsonline.com/getrag-6-spe...l#.YCQ0ii1h1u0
This is a vid from MM disassembling 3 420G`s

[Ascanio]

Originally Posted by grannyknot

I`ve spent a lot of time myself hunting for a rebuild kit, have never found one.
https://metricmechanic.com/
is one of the few companies that rebuild the 420G, they may sell you some parts.
You could also try, https://diffsonline.com/getrag-6-spe...l#.YCQ0ii1h1u0
This is a vid from MM disassembling 3 420G`s

Great info! Thanks
Do you know if they work on the ZF type H as well?

[ANILE8]

Originally Posted by Ascanio

In any case it seems impossible to source tranny parts, BMW distributes them only as whole packages, and ZF USA has proven completely unhelpful, to the point of referring me to distributors who no longer distribute them!

From everything I've heard, you are correct. These are a 'sealed' for life' unit from BMW and they just replace the entire unit. I know someone who blew their box and were waiting around 9mths to source a replacement from a wrecker.

If this happened to me, I would look at it as a mixed blessing and take the opportunity to swap in a sequential. There are so many options, Hollinger, Xtrac, Quaife, Samsonas. I would not be paying $$$ to fix an inferior gearbox.

[Ascanio]

Well “inferior” can be questioned, depending on what performance you are giving weight to.
The OE transmission is meant to be durable considering the mechanical stress it could be subjected to on road use, and comfortable for normal driving. Straight teeth will impact auditory comfort. Dog bite will make for extremely unpleasant use in city and traffic.
Sport/race gearboxes also require frequent costly maintenance, which adds up.

I remember one of my first mods ever, a set of Ohlins coil overs for an MX5, paid 2k for the kit, only to discover (the hard way) that I had to invest another 700 every two years to have them inspected. That is a trade-off that not everybody is willing to make. It depends on your intentions and what you are willing to sacrifice or not.

OE is usually the superior overall compromise, unless cost engineering was the leading factor, or even worse, mistakes were done. Which also happens.

[GuidoK]

I saw that a transmission shop local to me does sell a GS6-37BZ seal kit:
https://webshop.ganzeboom.net/gs6-37

However this is in the Netherlands. But I'm sure they speak english so they might be willing to ship to italy.
(I think these seals are common available bmw parts though and listed in the bmw parts catalog)
And maybe they know a solution to your worn synchro mesh.
I wouldn't be surprised that maybe older synchro mesh rings (that are still available) might fit, but this is such specific info that only persons who actually work with this would know.

[Ascanio]

Thanks!!

[ANILE8]

I think there may be some misinformation here we should clear up. Sequential boxes from several manufacturers are available with helical cut gears for lower noise as well as the more common straight cut gears for increased strength when noise is not an issue.

Dogtooth engagement simply replaces the synchros, clutched shits can still be performed as per usual should you want a 'smoother' shift at slow speeds. Everything wears out as have your synchros. The kicker is you cannot easily get a spare part for your OEM gearbox! For a race gearbox, replacement parts and serviceability is a prime design requirement.

Not sure who is trying to stitch you up for a $700 inspection fee on your coilovers every couple of years. Plenty on here including myself are running high-end aftermarket coilovers and if they are good quality and installed correctly there is no logical reason there should be any greater maintenance costs than OEM dampers so I don't buy that argument.

Fair enough if you don't want to modify your vehicle and want to keep everything original, I can respect that. But for many, mods are the reason we still have our cars and haven't upgraded to something else.

[GuidoK]

Originally Posted by ANILE8

Fair enough if you don't want to modify your vehicle and want to keep everything original, I can respect that. But for many, mods are the reason we still have our cars and haven't upgraded to something else.

Yeah but an aftermarket gearbox is a pretty expensive piece of kit.
A quaife unit will set you back easily $10k (ex fitting), and if you go for something like a Drenth, prepare to pay double.

[Ascanio]

Originally Posted by ANILE8

I think there may be some misinformation here we should clear up.

I certainly don't want to spread misinformation, on the contrary, I just like to think I help people make more informed decisions.
I can't say I am against aftermarket, after spending more than 50g on a Mazda MX-5. I would be the worst hypocrite.
But I have also seen my mental model shift widely after having been exposed for over a decade to automotive engineers as I designed cars in Italy.

Every piece of equipment is the result of design trade-offs: a multitude of "performance" targets including cost efficiency, lower cost of maintenance (durability and/or longer service intervals), comfort, safety, quality assutance, and.... road going performance, among others I don't even remember.

Carmakers have to juggle all of that, and it ends up being like when you go to bed in the winter and must choose whether you want the cover on your feet or your shoulders, because it's too small to cover you all at once. Yes there are exceptions to that, namely the Bugatti Veyron (reportedly costing 7.2mln Euros to build) and few others... I'm talking about things of common mortals.

Aftermarket "high-performance" and racing equipment are designed around entirely different objectives: sacrifice everything in order to maximise few critical performance targets. While OE parts are usually "generalists", aftermarket are "specialized". Depending on your intentions and expectations one might prove better than the other for you.

Racing gearboxes need servicing every few thousand miles (a Croatian friend running a Renault Clio complains of having to service its tranny every 3,000 miles, while cars racing in GT4 championships may run for as long as 8,000 mile intervals, I hear). OE transmissions are most often designed to last as long as the car without maintenance. Well... except for Audi's, but that's a different matter, and the reason why I hate Audi .
Therefore it's easy to find parts for racing and performance trannies, while it's nearly impossible to find parts for OE ones.

Regarding my Ohlins DFV Road & Track coilovers for the Mazda MX-5 NC, I intentionally disregarded the factory requirement to have them serviced every 3 years at the least (necessary to keep the 5-year warranty). I had one damper fail as I was joy riding on mountain roads on the border of France and Italy, while doing more than 150km/h, with a loud bang. No I'm not bragging, that is pretty normal driving for sportcar enthusiasts in that part of the world. Yes it is a driver's paradise. Nobody cares about the quarter mile there: in the twisties a well driven 160hp miata can stick to the tail of a RS4 pushing on all fours: it's about chassis, suspension, tires and skills.
The damper did survive a 1-hour long drive to my mechanic before being sent to the official service shop along with the other 3, undamaged: it just needed oil and seals.

My two cents is just to understand what you gain and what you lose with each option on the table, so you can make an informed decision.

[GuidoK]

I agree that oem parts usually have a longer lifespan than performance parts.
Performance parts usually have a different design purpose, giving either more performance or more feel of performance (more feedback).
That usually includes stiffer components and more vibrations, subjecting parts to a harsher life.

There are ofcourse exceptions where certain OEM parts can have certain design flaws.
For instance the OEM z4 fcab's have quite a limited life (usually less than 60k miles). The powerflex polyurethane fcabs I have in my z4 have had a longer life (both in miles as in years) than the original oem ones and are still pretty much like new.

[Ascanio]

Did you notice more NVH with poly bushings? Did you do just front or full-round? Do you have aftermarket dampers/springs also?

I am still deciding whether to go stock or poly. I don’t want the Z4M to go any stiffer than it is already, especially given how shitty the roads are in GA (no judgement there, it’s the same in Italy, and I HATE driving my MX5 with purple Powerflex around town down there, it is a nightmare).

[GuidoK]

Originally Posted by Ascanio

Did you notice more NVH with poly bushings? Did you do just front or full-round? Do you have aftermarket dampers/springs also?

I am still deciding whether to go stock or poly. I don’t want the Z4M to go any stiffer than it is already, especially given how shitty the roads are in GA (no judgement there, it’s the same in Italy, and I HATE driving my MX5 with purple Powerflex around town down there, it is a nightmare).

With just the fcabs the difference is négligeable.
It's like driving with new bushings all the time.
Adding polyurethane bushings on the anti rollbars also gives a similar effect.
Not really more NVH, but more a sense of that the car is a bit more planted.
Similar to the difference between a new car and a car that has done 100k miles.

My car is now completely polybushed (the front is shore80A, the rear is shore90A), I have stiffer anti rollbars, stiffer engine mounts and a KW V3 set (with linear springs; the normal z4 kw v3 set comes with linear springs, where the z4m kw V3 set comes with progressive springs).
I estimate the KW V3 set adds about just as much NVH as all the other mods I did to the suspension.
So all in all I have more NVH (and yes, I've been to italy lots of time, driving lots of miles on the back roads there), but it's ofcourse all adding up to a total sum.

If your preference is not to add lots of NVH, don't get a set of coilovers, and don't lower your car. Those give the biggest change in NVH imho.
However, polyurethane bushings on the front control arms and on the antirollbars are I think good upgrades that add little or no NVH and still give a more planted feel of the car.
Powerflex also has really nice poly engine mounts where you can tune the stiffness (but sadly pretty expensive too).
New engine mounts also give a more solid feel in the front. For example when taking a small roundabout, when you leave that you can feel the engine wobble a bit like a pendulum. Better engine mounts completely solve that problem.
On the rear the front trailing arm bushings are an interesting upgrade in polyurethane as they reduce tramlining a bit (use shore90a or shore95a here) The rest of the bushings are less important here I think.

[Ascanio]

Thanks! Good to know.

The purple Powerflex did make a lot of difference on the Miata, as did the various engine mounts I tried when I swapped a built 2.5 engine in it (to the point I seriously feared the cradle would crack!).

[Ascanio]

Originally Posted by Ascanio

Great info! Thanks
Do you know if they work on the ZF type H as well?

Had a chat with them, they sound like experienced guys.
Said the synchro is probably OK the issue is a design flaw in the transmission where half the teeth are slightly longer and end up engaging before the synchro does so properly, once the synchro has been bedded in.
They rework the whole tranny for 4g to make it bullet proof, for racing applications.

I’d love to do that but don’t want to spend that kind of money at the moment on a daily. I will keep their number in my priority list if and when I’ll have to do engine work in the future.