Hello,

I recently bought a 2003 X350 XJ8 SWB as a project car, and one of the mods I was thinking about is changing the gearbox from the 6HP 26 to a 8HP 70
I konw that X351 came with an 8HP 70 and an AJ 50 engine, so does anybody know if bell housings on the AJ 42 and AJ 50 are the same?

(I also saw that X250 3.0 D went from 6 speed to 8 speed in 2011 - so I am hopefull)

As background, I am an eDrive developement engineer and I used to work for ZF - but in their less famous eDrive division, and now I work for Magna. I have sent a question to some ex clleagues, and If i get something forom them - I will also share.
aslo, depending on the budget developement, I am also considering the 8P75HZ from a BMW 330e - with a 48V MHEV - but that's a 50/50 chance that I will go trough with it.

Thank You in advance for any help and I will start a build thread as soon as i get my ducks in a row.

 

the diesel is

 

What would be the fate of the J-Gate?

 

Well, I dont like the new controllers, so J gate would be re-engineered to provide signals to 8HP - but still look stock

 

Why not acquire the 8HP70 with the Chrysler V8 and cure the short longevity of the fragile "maintenance item" AJ motor at the same time?

 

Well ... I live in Wien Austria, if I was in Vienna, VI it would be a possible solution, here, It would be nearly ungegistrable !

 

I am assuming the number "6" would no longer mean "up to 6th gear", but rather "up to 8th", and the rest would retain its original behavior...? I.e. "5" would still mean "up to 5th", etc.?

I am super-curious if the fuel consumption will be significantly lower. 😲

 

May be I make shorter detents and fit all 8 - that would be cool, and with the way (HP is controlled - an aftermarket TCU would alow for a lot of aditional features.
As for fuel comsumption - there should be some gains.
And If I go for MHEV may be even a bit more - but addes weight would not help - but the main idea behind this aditional effort would be the torque gain.

 

No question it is a good transmission, but...Same chassis & mass. Same differential. Same 'ESO" (Engine Shaped Object).

I don't see where there's gain enough to matter unless some of those other bits are to be altered as well?

 

What is wrong with the 6hp26 that you would want to swap it out? Wish there was easily accessible software to flash different transmission tunes like the bmw crowd does. What a difference software tweaks can make.

 

As far as I know, the TCM speaks to the ECM while shifting to reduce torque. As TCMs compatible, so the ECM will understand ? Or do you need to write a converter for this ?

 

Hi OBM_Wien,

I don't know if the performance gains would be worth the trouble on a normally-aspirated X350, but it is probably possible to do the swap.

There is a lot of info online about guys fitting 8HPs to high-performance cars. Here's a video I saw recently:


For the record, I have a client with a BMW M550i xDrive with the 8HP75 that is having disturbing harsh shift problems at just 80K miles, and there are online accounts of others having similar experiences with the higher-powered BMWs.

Cheers,

Don

 

Ah, I have seen most of the videos on this chanel. I do not expect mutch speed/acceleration gains if i go to an 8HP70 - may be just some fuel consumption
8P75HZ would give some performance without building the NA engine
The point of this whole car / build is to be a project for me to play with, have fun - it won`t be a daily or a race/drag maschine.
As for ZF 8HP product quality - oh I am very well aware that there are good and bad variants - I did work for them ...

 

Theres the rub. The SIX speed slush box ain't exactly 'orrible. And the AJ Vee motors tend to want to eat all the play-money rations for their own selves.

That part is endemic. Like it or never, "play with it" you surely shall!

Not as if it just rolled out of the factory door yesterday afternoon, is it?

Only for a little while. Then the cost in time and treasure groweth tedious.

Those limits/prohibitions are 'designed in' // 'in the Levis' AKA genes, as well...