2004 XC90 auto - no drive when warm
 

2004 XC90 d5 auto ceases to drive once it is up to temperature.
Car will just lose drive and rev like a manual that has lost its clutch.

It has 220k on it. Gearbox never serviced in my time, probably never in it's life.
I gave it a sump dump and refill with the correct fluid. I believe I have got it to the correct levels.

It drove pretty well while I tried to get it to 80degrees to get a final level reading. As soon as it hit 70degrees box temp it lost drive. Won't engage drive or reverse. It probably will when I go back to it later once it has cooled down.

Can some explain what happens at the operating temperature that causes this?

Thanks,
Anton

Probably because the transmission fluid is new in an old transmission, meaning its thinner than the older fluid especially when warm and its causing slippage. There's bound to be wear at 220,000 miles.

Servicing an old transmission is always a gamble. At that mileage, it was probably best left not being serviced, especially as there were no records of it ever being done before. Looks like it didn't pay off this time, sadly. It could also have been a case of the transmission having a problem that wasn't relating to the fluid, meaning even changing it would have made little difference, but you don't know that until you try.

You'd need to bring it to a gearbox specialist for a proper diagnosis. Could need a new valve body or a full rebuild. Either isn't cheap and would outweigh the value of the car. That's just being realistic.

Sorry I didn't explain the situation correctly.
It was already without drive before I changed the oil. The oil change was a cheap quick attempt at rectifying it, to no avail.

You are completely correct on the last bit. It may be worthwhile throwing a box into it but it would have to be cheap to justify it. I can do the work myself but anything other than that and I may as well break it or weigh it in

I guess it depends on what its worth to you. Its a 20 year old car with 220k... its not worth much value wise, but it may have sentimental value.

If you can get a second hand transmission and are happy to keep her on the road, why not I suppose?

Depends what’s important to you. Ours only has 115k but it’s a 05 and not worth a lot. Probably less than the cost of a box rebuild but we would still do the fix as there isn’t another car that comes close to doing what we need as this.

It just depends if the car has value to you not just pounds value.

No sentimentality about it. Have had it 4 years and put 60k on it.
Haven't had to do much work to it, couple of engine mounts, couple of bushings and the regular engine oil.
Could really do with a water pump and timing belt shortly but that will only happen if I can get the auto box working.
AWD has never worked, not really been a big issue as it was bought for the space.

It now stalls when engaging drive or reverse.
I think I will drop the oil again, refill and see if that makes any difference. Worth a try.
I unfortunately don't understand the workings off an auto to understand or try to work out what is actually happening within the box.

No one understand these bloody boxes at least no one willing to fix them for less than thousands and even those people don’t really fix them they just pop in a recon unit. Shame really. Sounds like you’ve had your use out of it though.

the parts to recondition these gearboxes are expensive dozens of clutch plates and multiple valves and bearings and new fluid and that's before any labour to remove it from the car and strip it down. watch the youtube vid on the aw box stripdown to understand how complex this process is:regular_smile:

Watched a few of them and they are a Pandora's box!

I think the best option is to find a second hand box at £2-300 and throw it in it.
Does anyone know would the box from the 2.5t petrol fit and have the same ratios or is an AW55/51SN all exactly the same?
There is a full 2.5t auto for sale locally that is out of MOT at reasonable money.

2wd and 4wd are different boxes lots of cross referencing will be needed to match a compatible box as they will have different electrical connectors as well