Gearbox Fluid change (8 speed ZF)

[tonycordon]

I know that the gearbox of my '13 XF Sportbrake is 'sealed for life', but I am hearing opinions saying that a fluid change, which involves a new sump pan and filter is beneficial and that the difference can be 'felt' whilst driving. My car has covered almost 90K miles, I have owned it for 7 years and intend to keep it for as long as I can. So, does anyone have any relevant experience?

[fatboy b]

I think I it’s a 70k miles job and around £450 at a good Indy. Worth doing soon. Transformed the gear changes in my XFR-S, which we’re starting to get a bit harsh when cold.

[a8hex]

sealed for life == should last as long as we will sell you a warranty

[fatboy b]

a8hex said:

sealed for life == should last as long as we will sell you a warranty

It’s not though. ZF recommend every 70k

[Panamax]

tonycordon said:

So, does anyone have any relevant experience?

A precautionary change on any sealed transmission is never going to be wrong around 10 years or 100,000 miles so long as it's done proplerly.

I would not expect it to make the slightest difference to the way the car drives. In basic terms, if the fluid's knackered the transmission is probably knackered. The objective is to replace the fluid before any of that happens.

It's interesting that many people fret about their transmission fluid but never give the differential a second thought.

[MCSV8]

I've just replaced the fluid in my 92k miles 2011 X351 Supersport (6 speed ZF) with genuine ZF fluid and filter.

Diff oil also changed with amazingly expensive Castrol BOT720. Annoyingly, the LSD takes 1.25l and it's sold in 1l containers !! The non-LSD takes <1l .

Only as a precaution, and absolutely no difference noticed.

Makes me feel warm and fuzzy inside, though.

[fatboy b]

Panamax said:

A precautionary change on any sealed transmission is never going to be wrong around 10 years or 100,000 miles so long as it's done proplerly.

I would not expect it to make the slightest difference to the way the car drives. In basic terms, if the fluid's knackered the transmission is probably knackered. The objective is to replace the fluid before any of that happens.

It's interesting that many people fret about their transmission fluid but never give the differential a second thought.

Totally incorrect.

As said, the gear changes on my XFR-S were improved immensely when cold after a gearbox service. The box wasn’t knackered.

[Panamax]

fatboy b said:

Totally incorrect. As said, the gear changes on my XFR-S were improved immensely when cold after a gearbox service. The box wasn’t knackered.

Then I'll bet cash money the specification of the replacement fluid was different from whatever was taken out. Either that or your old fluid was full of bits of transmission.

I've had precautionary fluid changes in a number of cars and it's never made the slightest difference.

[stevemcs]

Panamax said:

Then I'll bet cash money the specification of the replacement fluid was different from whatever was taken out. Either that or your old fluid was full of bits of transmission.

I've had precautionary fluid changes in a number of cars and it's never made the slightest difference.

I think it’s a little bit of both. Our local transmission company said sometimes your better off putting the money towards a new gearbox if the fluid has been in there a long time, the valves and solenoids get used to it and cannot cope with new fluid.

[fatboy b]

Panamax said:

Then I'll bet cash money the specification of the replacement fluid was different from whatever was taken out. Either that or your old fluid was full of bits of transmission.

I've had precautionary fluid changes in a number of cars and it's never made the slightest difference.

Performed perfectly after the change with the same spec oil. Have a look on the ZF website. Says much the same there. You’ll do more damage leaving old oil in. And there is a filter to stop the big bits travelling about. Regardless, exactly what is wrong with changing the oil?

[mmcd87]

Panamax said:

Then I'll bet cash money the specification of the replacement fluid was different from whatever was taken out. Either that or your old fluid was full of bits of transmission.

I've had precautionary fluid changes in a number of cars and it's never made the slightest difference.

The fluid degrades over time and as clutches wear etc it contaminates the fluid. It's no different to changing engine oil really.

Cars that have had nice long motorway journeys would benefit less from those driven in town or as a weekend b road toy - fluid will have had an easier life.

[liner33]

Most specialists will tell you to service the ZF gearboxes every 60k, plenty of places do it and the cost is typically around £500 give or take. Lots of mobile companies do it as well

If you want to do it yourself there are how-tos on youtube and Autodoc stock the kit fairly cheaply around £200 typically, its an easy enough job if you have a ramp or can get the car high enough

There is an "old" school of thought that replacing the fluid on a high mileage transmission is risky and can cause failures and there is a lot of truth to this on older cars, bearing in mind how complicated the ZF is I would probably still risk it


Any gearbox "sealed for life" will have a shorter life

[Panamax]

The two posts above kind of fit together.

So long as the fluid hasn't been overheated, which will rapidly degrade it, the most likely think for it to contain is microscopic dust from the clutches etc. That dust in the fluid can actually help a worn transmission to keep on working because it makes the fluid "grippier".

The life of transmission fluid is very different from engine oil which gets contaminated by combustion products and unburnt fuel. That's really the only reason modern, synthetic engine oil needs changing at all.

[reddiesel]

Panamax said:

The two posts above kind of fit together.

So long as the fluid hasn't been overheated, which will rapidly degrade it, the most likely think for it to contain is microscopic dust from the clutches etc. That dust in the fluid can actually help a worn transmission to keep on working because it makes the fluid "grippier".

The life of transmission fluid is very different from engine oil which gets contaminated by combustion products and unburnt fuel. That's really the only reason modern, synthetic engine oil needs changing at all.

You made me smile there when you mentioned the dust making the fluid " grippier ". I well remember a chancer at the end of my road when I was a kid adding sawdust to the transmission of an old Bedford CF . Straight back through the Auction next day and onto the next one . Great days .

[fatboy b]

Panamax said:

The two posts above kind of fit together.

So long as the fluid hasn't been overheated, which will rapidly degrade it, the most likely think for it to contain is microscopic dust from the clutches etc. That dust in the fluid can actually help a worn transmission to keep on working because it makes the fluid "grippier".

The life of transmission fluid is very different from engine oil which gets contaminated by combustion products and unburnt fuel. That's really the only reason modern, synthetic engine oil needs changing at all.

You could always just accept you’re wrong and go get a fluid change

[mmcd87]

Panamax said:

The two posts above kind of fit together.

So long as the fluid hasn't been overheated, which will rapidly degrade it, the most likely think for it to contain is microscopic dust from the clutches etc. That dust in the fluid can actually help a worn transmission to keep on working because it makes the fluid "grippier".

The life of transmission fluid is very different from engine oil which gets contaminated by combustion products and unburnt fuel. That's really the only reason modern, synthetic engine oil needs changing at all.

There is more to think about than you are perhaps implying. Torque converters contain a lock up clutch which contaminates fluid over time, bridge seals to valve body can degrade over time which promotes wear due to reduced valve body pressures (recommend changing same time as filter).

The fluid properties are very important for these gearboxes to allow the clutches to work properly - a lot of people get stung using more generic fluid than exact spec. 'Dust' just collects in the valve body / mechatronic unit and thus gives poorer control and promotes further wear. Changing the fluid is definitely the way forward - ZF themselves say to do it against the 'sealed for life' of the car manufacturers which is only done to reduce cost / get it through warranty. Honestly, change the fluid as per ZF recommendation.

[Biggy Stardust]

It's not "sealed for life" it's "filled for life".

It can be refilled for longer life. I did it on my XK & it improved the gearbox from pretty smooth to absolutely perfect.

[Winco]

I changed the gearbox oil and pan/filter on my '13 XF Sportbrake myself. Done 71K, Purely preventative, the old oil and pan didn't look too bad. For oil, I used Westway Oils. 10L for £66 for their ZF 8 Speed fully synthetic.

I also changed the diff oil and used Castrol Syntrax 75W-90.

For both I used a small 12V fluid pump to transfer the oil uphill into the fill ports.

[Panamax]

Winco said:

For both I used a small 12V fluid pump to transfer the oil uphill into the fill ports.

That's a good call. So many fill plugs are difficult to access, the components being filled before they're bolted in on the production line.

[Velindajag]

Interesting discussion Thanks guys.
I think I will get XF 3.0 Diesel gearbox oil changed next service in August at 12 years 60k miles just to be safe.