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[Scatmancraig]

I have an Omega 2.5TD with the AR25 autobox. Now I know that this gearbox can be something of a weak point in the vehicle. I'm not 100% convinced that the one in mine is in perfect health....

It might be my imagination, as I haven't owned an automatic car for a few years now, but I think the gearbox is just a little too slippy at times. It's also slow to engage reverse, probably 1-2 seconds instead of instantly when you put it in Drive. Other than that, it goes through the gears ok, and the torque converter locks at just under 50. It kicks down like it should too. It's just the engine revs sometimes hardly change when it changes gear, especially on light throttle.

The car is on 163k, so not in the first flush of youth by any means. It was originally a HSBC company car up to 100k, and I have their service history print out confirming that the box was replaced at 70k. So the one in it may well have over 90k on it now. The engine is standard, and I have no immediate plans to start messing with the ECU as it seems to pull like a train as it is.

Do you think it is worth me changing the gearbox oil and filters, or leaving it as it is and putting the cash towards upgrading it to an AR35 box (if I can find one)?


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[Nick W]

Have you checked the fluid level?


Or you could drop the gearbox sumps, clean the filter and reassemble with sealant rather than gaskets. That will cost you about £20 worth of ATF, and you'll be able to examine the condition of the fluid that's in it.

[Scatmancraig]

Have you checked the fluid level?


Or you could drop the gearbox sumps, clean the filter and reassemble with sealant rather than gaskets. That will cost you about £20 worth of ATF, and you'll be able to examine the condition of the fluid that's in it.

How do you check the fluid level on these?  As I can't see a filler tube.  Something in the back of my mind tells me that they don't have one, I know the BMW 530D I had a few years back didn't.

I can get the filters and gaskets easily enough through the ABS club.  But even then, with the cost of the fluid, it's still a fair few quid to do the job.

[Nick W]

Have you checked the fluid level?


Or you could drop the gearbox sumps, clean the filter and reassemble with sealant rather than gaskets. That will cost you about £20 worth of ATF, and you'll be able to examine the condition of the fluid that's in it.

How do you check the fluid level on these?  As I can't see a filler tube.  Something in the back of my mind tells me that they don't have one, I know the BMW 530D I had a few years back didn't.

I can get the filters and gaskets easily enough through the ABS club.  But even then, with the cost of the fluid, it's still a fair few quid to do the job.

Stupidly, there isn't one. The level check procedure is to drive the car ensuring that it's been into all four gears and the ATF is up to temp. With the engine running you undo the filler plug on the gearbox and add fluid until it dribbles out of the hole. Easy if you can drive it onto a ramp, but a right pain if you're stuck with axle stands


To keep the costs down, buy the gaskets, and clean your existing filter.

[TheBoy]

They all seem to have a lot of slip.

However, don't mess about, get an AR35 on it, and then get the bugger chipped. Its not about speed, its about making it more drivable with a better power delivery.

[Scatmancraig]

They all seem to have a lot of slip.

However, don't mess about, get an AR35 on it, and then get the bugger chipped. Its not about speed, its about making it more drivable with a better power delivery.

How difficult is it to swap for an AR35?  And does it matter what the AR35 came off in the first place?  (for example, if I can get my hands on a Senator AR35, can it be used?) 

I'm not at all disappointed with the power delivery.  Although I have owned multiple Carlton and Senator 3.0 12v and 24v's, I haven't had any for a few years now.  I spent nearly two years without without a car (don't ask!) and for the last year my drive was a Peugeot 106 1.5 Diesel!!  So even the detuned version of the Beemer engine in the Omega is a world apart from what I have recently been used to!!

[TheBoy]

Simple in principle, but often quite fiddly, and its bloody heavy.

Unbolt TC from flywheel (3 bolts on TD). Unbolt driveshaft from gearbox (6 bolts IIRC). Unbolt gearbox from engine casing (about 8 bolts), disconnect electrics.  With box off, swap over TC and bellhousing.  Refit is reverse, ensuring that TC is attached to gearbox before fitting gearbox to engine.

[Scatmancraig]

Simple in principle, but often quite fiddly, and its bloody heavy.

Unbolt TC from flywheel (3 bolts on TD). Unbolt driveshaft from gearbox (6 bolts IIRC). Unbolt gearbox from engine casing (about 8 bolts), disconnect electrics.  With box off, swap over TC and bellhousing.  Refit is reverse, ensuring that TC is attached to gearbox before fitting gearbox to engine.

My main issue with swapping the box will be lifting the replacement back in. I've removed a couple of AR35's before, but always replaced with R28 manuals, which are a good deal lighter. I might be able to fashion a cradle to attach to my 2 tonne trolley jack to assist. Sounds like a straightforward enough job though.

[Shackeng]

JamesV6CDX swapped mine with a little encouragement from me, and made it look easy. IIRC we used two jacks to lift it into position.

[Bigron]

Just 80 miles from you to Serek's garage in Huntingdon for a perfect job.....

Ron.

[Scatmancraig]

Bearing in mind that I can get the filters and gaskets quite easily, I'm going to give that a try first.  My budget won't stretch to a replacement box while I still have other parts to get.  As it is, the gearbox still works and the car drives ok once warmed up, and several people have said that changing the filters and fluid does them good, so I will report back once this is done.

[tigers_gonads]

Not teaching you to suck eggs or anything but when you check the level, make sure the engines running and the car must be level on stands or ramps before you remove the filler plug 

[Scatmancraig]

Not teaching you to suck eggs or anything but when you check the level, make sure the engines running and the car must be level on stands or ramps before you remove the filler plug 

I was working out in my head how to do that and still be able to get under the car. I used to put a spare wheel under each front or rear wheel and use axle stands at the other end.  Need new axle stands though as someone had nicked my last set.

[Entwood]

Cheats way if you have problems .... park the car, on a flat level surface, engine running, through the gears a couple of times then leave the engine running, then jack up from the side with the filler plug, remove filler plug and add oil until it just starts to overflow, position something to catch excess oil, lower the car back down and leave until oil ceases to drip, jack back up and replace filler plug, lower to ground and switch off engine ....

job jobbed 

bit of a faff but if getting the car high and level is a problem then it works !!! 

[Scatmancraig]

Cheats way if you have problems .... park the car, on a flat level surface, engine running, through the gears a couple of times then leave the engine running, then jack up from the side with the filler plug, remove filler plug and add oil until it just starts to overflow, position something to catch excess oil, lower the car back down and leave until oil ceases to drip, jack back up and replace filler plug, lower to ground and switch off engine ....

job jobbed 

bit of a faff but if getting the car high and level is a problem then it works !!! 

That definitely sounds like the way forward, once I've replaced the filters and sump gaskets.

Can anyone tell me what the total fluid capacity of the AR25 transmission is please?

[Bigron]

Nearly 9 litres, IF you can get all of the old ATF out.....

http://oldsite.omegaowners.com/forum/YaBB.pl?num=1289757627

That's an old guide and for an AR35, but basically the same with a few handy tips.

Ron.

[Scatmancraig]

Nearly 9 litres, IF you can get all of the old ATF out.....

http://oldsite.omegaowners.com/forum/YaBB.pl?num=1289757627

That's an old guide and for an AR35, but basically the same with a few handy tips.

Ron.

I've heard before that it's best to do two fluid changes a short period apart, so that any remaining old fluid stuck in the torque converter is diluted as much as possible.

I'm wondering if it's cheaper to get the Dexron III ATF through Trade Club?  As it's quite a decent amount that is needed.