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[daveb]

Hi everyone.

I have a year 2000 facelift Omega 2.5TD CD AUTOMATIC (BMW engine) and have a gearbox query.

I understand that there were two different auto boxes fitted to these, I think they are called AR25 and AR35, but can't be sure.

I am interested in increasing the performance of my car as I understand that the BMW engine was de-tuned quite a bit when put in the Omega.

I understand that the '35' one is the better one to have if I increase power as it is able to better handle the increase in torque.

Is any of this true, or am I dreaming.

If this is the case, how can I tell which gearbox I have fitted. Is there a visual way I can find out, or can I tell from the chassis number or any other associated documentation I have for the car.

Any help appreciated.

Great Forum by the way - managed to upgrade to cruise following advice on this site. £8 for the stalk - then plug and play - wahey - worked straight away. Wouldn't have ever thought of trying until I joined this site - Thanks!

Dave.
 

[Matchless]

Im sure Mr McBurger will be along with the details soon but Im sure you have the AR25, and I gather its a bit marginal on torque capacity. The AR35 is the better box, mated to your existing torque converter.

[mijfife]

Hi Dave, I've just refitted my gearbox and I noticed that there is a green ID plate on the left hand side of the box about half way along. You should be able to read this in situ. I'm assuming yours might be the same??

Cheers Jim

[daveb]

Hi Dave, I've just refitted my gearbox and I noticed that there is a green ID plate on the left hand side of the box about half way along. You should be able to read this in situ. I'm assuming yours might be the same??

Cheers Jim

Hi Jim,

Left hand side is nearside isn't it!?

What does it say on your green ID plate ?

Thanks.

Dave.

[mijfife]

Hi Dave, yes left hand is nearside, I supose if you're lying on your back under the car it's technically on your right hand side   As for what's on my green plate, I can't remember   i do recal seeing the AR code but I'm not sure if it is 25 or 35. I'll have a look tomorrow when I'm (hopefully) fitting the engine.

Cheers Jim  

[RonaldMcBurger]

Hi de hi. Autobox/TD combo. Just my stuff.

Ok, the box you have (if original) is an AR25. It is actually worse than that, it is the basic AR25 which is the same one used in the 2.0 16v Omegas. Problem is a lack of clutches and too much torque.

These boxes usually fail on 2.5TD's at about 120k - 140k. The main problem is that they forgot the huge torque the TD's produce, which basically knackers the box.

The answer is to replace the box with a good AR35 from a 3.0. Bellhousing is different, so that needs to be swapped, but you MUST use the original torque convertor. These never go wrong.

As for more power, yes you can get a whopping increase quite cheaply. Talk to OmegaToy when he gets back off his hols. He has tweaked his 2.5TD so that it will leave the 3.0 v6 behind (as long as it isn't running that is! ). Seriously, he has over 200BHP coming out of that TD engine.

So there you have it. Tweak and an AR35 box = one very fast and ultra reliable Omega Diesel.

[daveb]

Thanks for such a comprehensive guide Ronald McB.

Are AR35's easy enough to come by and what sort of cost is it likely to be. And what about the bellhousing - is that easy enough to get hold of?

Is fitting all this a DIY job for a novice like me or if a garage job, how many hours labour do you reckon on.

The power upgrade Omegatoy has achieved sounds highly entertaining - must do the same to mine!

Thanks for all the help so far.

Dave.