Transmission swap

[Herbmiester 939]

I am looking to swap the GM 6L45 in my 130i for a ZF6HP. Some of you may wonder whey swap an auto for an auto, but bear with me I do have what I think are solid reasons. Firstly and probably the big one for me, is the GM6L45 is an average box. It's not that smooth, especially when being pushed. It clunks up and down and does have a habit of chopping down when its not needed or holding on when it should drop down. I find it a bit of a guessing game. It does work ok when you use the paddle shifters. My 6l45 has had a service ad works as it should.

In comparison the ZF box's I have had are noticeably smoother. The y have a much more refined converter lock/unlock and shifts are smoother. It also seems to be a lot smarter about when it shifts up and down. Finally it can be made very sharp with an XHP flash tune. Having had 6HP boxes in a few cars now and have always been impressed. 

The question of why not manual convert is a simple one, at best its a 5k job and could easily be 7k plus. One the other hand the ZF swap is a 1 to 1.5k job. Also my wife drives the car in Wellington traffic and is not interested in having a manual. I can get my manual fix driving the E34. 

Getting the right ZF box is the key and there are a few small parts needed. I am pretty sure I can do it myself (using a lift), and again if the right box is used, no reprogmaing of the TCU or DME is required. I am still gathering information but  this article from XHP covers it. I am in the market for a ZF 6HP19/21.

https://www.xautomotive.com/blogs/news/from-gm-to-zf-6hp

 

[Eagle 1683]

Biggest issue for me would be the used auto box gamble. You'd probably do a service, mechatronic seals etc and probably a few drain and fills so that's another $700-800 on top. Then you kinda have to hope the rest is ok because they do have quite a few potential faults that can occur.

Getting one from a damaged working car or something the you can at least test drive, check adaption values and fluid condition would be good, or even having it inspected\rebuilt.

[Herbmiester 939]

Yes getting the right box is the key. My research, including a good chat with the local transmission guy, painted a decent picture on ZF6 reliability. He really doesn't like the 6L45. 

[Kiwi_BMW 90]

Why don't you fit a 8hp45, it would bolt up to the N52 and Cantcu controller.

While the 6hp works quite well it isn't as smooth as the 8hp

[Herbmiester 939]

An 8HP is an awesome trans and I have driven, and owned a few cars that have it. However, it's quite a bit more expensive to buy, and there is no simple "how to" guide to fit it. I dont know if I will need new driveshaft, what trans mounts will work and the fact the Cantcu controller is $2k. The 6HP is a simple bolt-up and the DME talks to the TCU with no programming needed.

[Olaf 3352]

yep, the ZF6HP is an excellent box, and given it appears to be a relatively simple swap, indeed why wouldn't ya?   The ZF8HP is astonishing at its smoothness and intelligence; I can't vouch for more or lesser longevity or reliability of 6HP vs 8HP.   I agree with what you're saying John, there's a big difference between swapping in a trans that the car is engineered for, and customising an entirely different trans swap.

I'm in the same camp - I certainly love the manual driving experience, a conversion would not get a look in with anything my wife drove even infrequently.  I drove manual in Mexico City for ~2.5 years, if I was doing that again it'd be auto all the way.  Modern autos are bloody brilliant.
 

 

[Vass 872]

2 hours ago, Olaf said:

I drove manual in Mexico City for ~2.5 years, if I was doing that again it'd be auto all the way.

 

[Olaf 3352]

it's okay mate, heel-and-toe double de-clutch downshifts with blips when I'm pedalling a manual 😁

[Kiwi_BMW 90]

On 12/27/2024 at 11:18 AM, Herbmiester said:

An 8HP is an awesome trans and I have driven, and owned a few cars that have it. However, it's quite a bit more expensive to buy, and there is no simple "how to" guide to fit it. I dont know if I will need new driveshaft, what trans mounts will work and the fact the Cantcu controller is $2k. The 6HP is a simple bolt-up and the DME talks to the TCU with no programming needed.

The 6HP19/21 and 8HP45 are the same length, and the rear flange from a 6HP can be fitted to a 8HP, so the same d/shaft should work.

The rear mount would be an easy adaption, although from what I have read there are several different cross members and one maybe a bolt in fit.

That leaves one mechanical issue, the trans cooler pipes are different size between the 6HP and the 8HP, not sure about the 6L

Cantcu supports many electronic shifters and operates seamlessly in a oem way.

Yes it is a bit more expensive but a 8HP is younger and most likely in better condition than a used 6HP

[Herbmiester 939]

I did some checking and an 8HP starts at around 3k, plus 2k for the Cantcu, that's 5k plus working out the cooler swap parts. I can do the 6hp for about 1.5k. While its not as good a trans, with an XHp tune it's a pretty good. The 8hp can be someone else's project. 

Edited December 29, 2024 by Herbmiester

[HELLBM 1561]

2 hours ago, Herbmiester said:

I did some checking and an 8HP starts at around 3k, plus 2k for the Cantcu, that's 5k plus working out the cooler swap parts. I can do the 6hp for about 1.5k. While its not as good a trans, with an XHp tune it's a pretty good. The 8hp can be someone else's project. 

We have plenty of good 6HP's $750 each or 8HP $1500 each @HELLBM

[Neil McCauley 399]

@HELLBM done any M57 8HP swaps yet?

[HELLBM 1561]

8 hours ago, Neil McCauley said:

@HELLBM done any M57 8HP swaps yet?

Only Manual

[Driftit 2095]

I'm actually quite keen on this myself John.
My commuter 130i had its box serviced at some stage by someone that did not fill it correctly.  Caused the dredded low speed shudder.  I sorted the shudder but the box changes pretty harshly sometimes and often "slips" going up a gear from 2nd to 3rd.

I would probably go with the ZF6 for this car.  As I already have a manual 130i for the fun stuff.
I was also just looking at the S55 DCT adapter for my M30 in the E34 too.

[Herbmiester 939]

 

Dan, I am keen to do this sooner rather than later. My 6L45 shudders and clunks gears similar to yours and mine has also been serviced. If you do this let me know I will pop over the hill and give you a hand. (If you need it  )

[Driftit 2095]

37 minutes ago, Herbmiester said:

 

Dan, I am keen to do this sooner rather than later. My 6L45 shudders and clunks gears similar to yours and mine has also been serviced. If you do this let me know I will pop over the hill and give you a hand. (If you need it  )

I'll start really looking into it.  I have other gearbox tasks for the E34 and Merc E55 I am also working on right now so I will pick up a gearbox jack asap to make things easier.

I had the manual box out of the other 130i recently which was a pretty quick job.
Good chance to do the rear main and guibos.

Is any programming needed?

[Herbmiester 939]

If you get the correct box no programming is necessary, you just have to re pin the connector. Full instructions on the XHp blog. https://www.xautomotive.com/blogs/news/from-gm-to-zf-6hp