A8L 4.2TDi gearbox service questions?
 

Hi there,

I have been looking to get my gearbox serviced properly since I bought the car nearly 5 years ago. I was close once where I drove the 700 mile round trip to Mackie in Glasgow, dropped it off late one afternoon, decamped to a hotel but then got a call in the morning to say they had the wrong parts for my particular box but that there was also an oil leak that meant the transmission would have to come out!

As this was on 17th March 2020 and we were steaming towards the first COVID lockdown I never did get round to booking it back in.

I have driven all around the UK and across Europe before and since and don't have any issues but as I have now hit 169k miles and I will hopefully have some spare cash figure now is the time to get it booked in.

In the 5+ years since I have had the car it has never left a drop of oil on my pattern-imprinted concrete drive and checking the service history see it had an oil leak repaired prior to me buying the car back in March 2018 so can assume the box doesn't need to come out.

I have also asked if they can replace the oil in the front diff/transfer box and the rear sports differential while they have the car in but they tell me, quote;

"With regards to the sport diff and the transfer box these require carrying out with pressure bleeding equipment, also the transfer box is combined procedure along with the front diff of the gearbox. Which when they are in situation can be very tight to get to. So unfortunately, we wouldn’t carry out these procedures for yourself."

Disappointing to say the least as they do seem to have a reputation of being a first-class ZF Service Agent but is this task really as difficult as I am being told?

Have any of you guys ever carried out an oil change in the front diff/transfer box and rear sports diff? Possible? Impossible??

I must admit my first point of call back in 2020 was ZF themselves in Dortmund after reading some great reviews of Klaus & Co. but unfortunately they don't do service work any more and wanted to refer me to one of their authorised Service Agents of which Mackie are one. I believe they also told me that the oil changes on the differential are only carried out if there is a drain plug there.

Thoughts?

Thanks & kind regards,
-=Glyn=-

Never worked on a D4, but did the rear diff on my D2 when I had access to a lift (just prior to lockdown, ironically).

As for the D4, here's several videos on how to do it yourself. I've only watched the rear diff one, but all the relevant info is in the video or video description:

First three all by the same person.
Rear Diff: https://www.youtube.com/watch?app=desktop&v=9WeWN7UkZgg
Front Diff: https://www.youtube.com/watch?v=vDmXgynQHlI
Transfer Case: https://www.youtube.com/watch?v=oz3gftOh9mA

Transmission Fluid: https://www.youtube.com/watch?v=vDdOOzd2mJ8

The Edit option seems to have disappeared, so adding this here.

The following is another video on filling the ZF transmission, which has some more detail about the fill procedure. It was done on a BMW, but it's the same procedure:

https://www.youtube.com/watch?v=kXKhZievmSI

Thanks for the replies steamship...seems the more I research the more confused I get!

Some posts/videos refer to sports diffs on different models and the only references to A8 diffs don't seem to be the sports diff.

I have seen references to the sports diff having two different oils, the need to calibrate it afterwards which was why I was hoping the 'experts' at Mackies would step up to the plate.

Strange then that they did quote me back in 2020 to replace the diff oil but here we are nearly four years later and they are telling me they don't do it and need specialized pressure bleeding equipment to do so.

When I had the factory tour back in 2020 they showed me the dyno-cell where they take out transmissions and run them up under road conditions and emphasized they are able to remanufacture gearboxes/diffs/transfer boxes on site but here we are in 2023 and all of a sudden they don't have the equipment to change the oil in a differential.

This is not a job I would attempt myself but I do have a friend who is confident he can carry out the complete transmission service as he has worked on 8's before and has done the same work on Range Rovers which I also believe are fitted with the ZF8HP90 gearbox although I would think the diffs/transfer boxes would be different to mine.

Why is nothing straightforward these days? Must be the price we pay for 'progress; I suppose...

Thanks & kind regards,
-=Glyn=-

That's a bugger, and on a relatively newish car (compared to a D2). Hope you can get it sorted.

On a lighter note...

Singing from the Don Pettit NASA songbook:

"The problem is we don't have the technology to do that anymore. We used to but we destroyed that technology"