Sport Auto Transmission Difference 125/135

[BigshotMD]

Does anyone know if there are any differences in auto transmission build quality between the 125 and 135? Both are ZF gearboxes? Made in the same place?

Cheers.

[carbonaccord]

It's not the same. Only the 135i has the ZF gearbox.

[Lester]

There are several posts on this very topic right now - do some searching to catch up.

All 1-series AT's - except the 135 are using a varient of the GM 6L50R transmission made by GM in France, and used in a variety of GM cars including the Cadillac CTS. The 6L45R is a BMW OEM version and is used in the 32x series and all 1 series up to the 130.

The 135 is using a ZF - GA16HP19Z and is used in the 135 and 335.

As to quality, who is to say - I'm sure BMW has quality assurance in place with both manufacturers. Hopefully the ones made in France don't have pieces of croissant and brie cheese in them! :-)

[BigshotMD]

Originally Posted by Lester

There are several posts on this very topic right now - do some searching to catch up.

All 1-series AT's - except the 135 are using a varient of the GM 6L50R transmission made by GM in France, and used in a variety of GM cars including the Cadillac CTS. The 6L45R is a BMW OEM version and is used in the 32x series and all 1 series up to the 130.

The 135 is using a ZF - GA16HP19Z and is used in the 135 and 335.

As to quality, who is to say - I'm sure BMW has quality assurance in place with both manufacturers. Hopefully the ones made in France don't have pieces of croissant and brie cheese in them! :-)

Thanks for your input and apologize for the double post.
I have done all the catch up reading...I hope!

Yeah, just having some second doubts on my purchase, realising now that the AT in 125i/128i is manufactured by GM (hopefully, no brie in between..LoL). Maybe I should have gone with the 135i.

I thought I made an informed decision, accepting the fact that I didn't need the extra power output because of my life style (daily use, mostly in the city, with a lifestyle, unless called for rare emergency operations, will probably not need to travel greater than 80kph unless I feel like getting a speeding fine). The dealer told me that both gearboxes were identical. Didn't analyse the ratios and acceleration differences until now, noting the almost 0.6s difference in the 125/128 as opposed to the 0.1-0.2s difference in the 135i.

But I'm a bit concerned about this 125i/128 gearbox. I've come from a Audi DSG gearbox, which is pretty durable and arguably better than a manual gearbox. And as such, engine aside, I am wondering about the quality and performance of this GM gearbox.

But I've read and some people have tried to explained the acceleration differences:
- Not the gearbox, but because turbo holds their boost on AT in 135i hence the little difference in AT/MT gearboxes. In MT, turbos need to re-spool.
- If one where to theoritically put the GM gearbox into the 135i, the times would be the same.
- GM gearbox is 66pounds heavier, thus more heavy duty? i.e. Someone mentioned that if gearboxes were women, the GM is a size 10, less likely to get brittle bones when older, as opposed to a ZF, being a size 8?

But then I read on the same thread that the GM is much more inferior to the ZF gearbox, one that is made in germany as opposed to France? This same gearbox is in use in the Cadillac CTS, where the power/acceleration ratio was a bit doubtful. It is also used in a Holden Commodore in Australia...a bit depressing

Could someone please conclude and comment:
- Is the GM gearbox truly inferior? If not, please reassure my confused soul
- If I were to compare head-to-head the actual performance (i.e. gear shifting times) of the gearbox, they are the same?
- Durability wise, it can hold a bit of torture similar to the ZF?
- Does anyone know the factory cost of both gearboxes. Lester posted a good diagram of both gearboxes in another thread. It's the same cost for both gearboxes? If ZF costs more and GM much less, that means the profit margin for 135i is a lot lower?

Thanks a lot for your input and reading this long post.

[BrokenVert]

Maybe your dealer thought you were talking about the Manual trans? Becuase the 125 and the 135 both use the same manual box.

[Lester]

Originally Posted by BrokenVert

Maybe your dealer thought you were talking about the Manual trans? Becuase the 125 and the 135 both use the same manual box.

Actually, the 125/128 don't use the same manual transmission as the 135.

The 125/128 use the Getrag GS6-17BG. This transmission is also used in the 525 and 325/328.

The 135 and 335 use a different model of Getrag: The 135 uses GS6-53BZ-TJGK.
The 335 use a slightly different variant than the 135, model GS6-53DZ - THGX.

[BigshotMD]

so there is a difference for both MT and AT transmissions in both 135 and 125. Don't know what my dealer was talking about.

Maybe i should ask for a free upgrade for misinforming..haha, a bit late now.

[Lester]

The Manuals are at least from the same manufacturer - Getrag, and the same family - GS6. I am not sure what the subtle differnces are between the model numbers - 17BG for the 125/128 or the 53BZ on the 135. The 53BZ case looks a little heavier than the 17BG on the realoem parts drawings.

[BigshotMD]

well anyway, back to my original questions..any useful input would be great.

Cheers

[cimbali]

the GM auto is quite good as far as automatic transmissions go...in regular D mode you get good gas mileage at the expense of low end performance. In SD or manual mode you get great performance at low and high engine speeds. And the GM transmissions used by BMW have been very reliable.

[BrokenVert]

To Lester. I stand corrected.

[BigshotMD]

Originally Posted by cimbali

the GM auto is quite good as far as automatic transmissions go...in regular D mode you get good gas mileage at the expense of low end performance. In SD or manual mode you get great performance at low and high engine speeds. And the GM transmissions used by BMW have been very reliable.

Thanks.

Just that this is my first Bimmer. A bit of a noob.

Anyone have any problems with the auto transmission for the 128/125? In the other BMWs that use this same gearbox?

There is apparently 1 reported issue with the MT, with reverse gear, but maybe that's a incidental rather than a statistical issue.

I can't seem to find any problems with the gm transmission on the 128/125, so it's probably a good thing

[Lester]

Bimmerfest has a few complains about jerky shifting and performance in low gears on the GM tranny. One or two had to have torque converters replaced under warranty.