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[Webby the Bear]

Evening guys 

We're moving on to transmission at school and a couple of the lads were tasked with removing an autobox from an old 3 Series we have in there (N. reg perhaps). They pulled it out in pretty quick time and I went over to inspect said box and I was like... hold on a second... I've seen that box before...



So. What's going on here? It's got GM stickers and GM cast in to the side. It fitted like a glove. I've heard that it's a BMW box in the Omega... but why all the GM gubbins?

Here's the castings and stickers if it helps...



Please forgive me fr the questions I'm going to ask as its been a while since I've done transmission... but:

1.) On the back of the box you can just make out a hexagonal thing connected to the output shaft. is this a balanced assembly to even out the output forces and not cause vibrations.... and whats its name
2.) What is the selector switch for? I'm assuming it sends a signal to the ECU to tell it what gear position youre in after moving the shifter?
3.) I've read one of the big problems with these boxes aside from the ATF level is the selector switch needing cleaning... where do you clean? you have to open it up?

[TheBoy]

Certainly the TDS beemers of the era used the GM Hydramatic boxes, as used in our Omegas.

[Kevin Wood]

Yep, BMW used GM Strasbourg transmissions identical to the AR35 in quite a few models.

[Webby the Bear]

Interesting! So this bad boy would slot straight in to my car?

[Kevin Wood]

Interesting! So this bad boy would slot straight in to my car?

I'm guessing the bellhousing casting is probably different. The electrics and wiring might also differ, as might the gear ratios, but it's fundamentally the same gearbox.

[Ever Ready]

I think it is the Hydra-Matic 4L30-E

I have a couple of docs on it somewhere, who knows where though

[Kevin Wood]

I think it is the Hydra-Matic 4L30-E

I have a couple of docs on it somewhere, who knows where though

Yep, 4L30E is the designation for that line of gearboxes. It was used on everything up to the 328 / 528 in the '90's plus some of the 2.5td tractor engined BMWs.

[Webby the Bear]

Thanks boys. 

Anyone any idea on the questions relating to rear donut thingy and selector switch?

[Ever Ready]

If memory serves the selector lever is externally mounted on the passengers side of the box (rhd)

[Webby the Bear]

If memory serves the selector lever is externally mounted on the passengers side of the box (rhd)

It is mate  Was just curious about how to clean the switch though as it's a common problem on these I believe

[Webby the Bear]

Ps, I have read the guide regarding removing the switch. Loks a bit complicated with getting it aligned  Does it have to come off to clean it?

[Webby the Bear]

Actually looking at the guide I think I may have sussed it....

The inside of the switch is what needs cleaning as it's a system whereby the arm moves and changes resistance depending on it's position.... gets crud in there thus gives incorrect signals?

[Ever Ready]

I don't know how hard or easy it is to remove the selector in situ

Years of road crud can get in to most places, so maybe it would benefit from a clean

[henryd]

I think it is the Hydra-Matic 4L30-E

I have a couple of docs on it somewhere, who knows where though

Yep, 4L30E is the designation for that line of gearboxes. It was used on everything up to the 328 / 528 in the '90's plus some of the 2.5td tractor engined BMWs.

4 pot Z3,s got them as well

[Kevin Wood]

There doesn't appear to be a selector switch on that box. I'm guessing BMW sensibly used some sort of switch on the lever itself where it's in the dry but yes, as you say, it's to inform the ECU what position the lever is in. On the Omega it also operates the reversing lights and prevents the engine from being started in gear.

I'm guessing BMW used a different coupling to the propshaft. A rubber doughnut is often used to provide a little flexibility and to damp out shocks in the drivetrain, as you say.