Diff oil change question

[Andp]

Got a quote for changing diff oil in my 2007 3si manual and the garage has replied - but it seems that an extra charge may be made for the following reason : "being a 2007 Z4 you are unlikely to have a drain bung in the rear diff cover the only way we would expect to be able to change the oil would be to remove the diff take off the rear casing to drain the oil and then re-fit and re-fill in situ"
Is this correct?
Many thanks

ps extra charge would be £180 + vat

 

[GuidoK]

Yes that's a possibility, not having a drain plug.

But I wonder if they cant suck the oil out with a shop-air powered brake bleeder (that creates a continous vacuum on that hose) and a thin hose.
This is also the way bmw officially recommends doing the job on diffs that have no drain plug. They do not prescribe a special suction tool for that, but an automatic brake bleeder, or maybe an engine oil extractor can do it

Getting the diff out sure is considerably more work. 2 hours or so at least I guess to get it in and out, apply liquid sealant etc.

 

[biojo]

as said mine didnt have a drain plug so just sucked it out, you might be left with a small amount of old oil left in but not much

 

[Scooba_Steve]

Do you have to drop the diff to get the cover off? It's been a while since I've been under.

 

[nfbr]

My 2007 3.0si had a drain plug in the rear diff, but then mine is an Auto/Tiptronic

 

[Yorkie Z]

Do you have to drop the diff to get the cover off? It's been a while since I've been under.

You can remove the cover in place but its still time consuming. I speak from experience.

 

[Scooba_Steve]

Mine also has a drain.

As for the cover, still quicker/less faff in situ than dropping?

 

[stuartinzg]

if they don't know how to drain without a plug, suggest you find another more specialised garage

 

[dhobbs]

I asked munich legends to do mine and they came back with the same response. They did sample the oil and said it was fine (88k miles) so I didn't worry too much.

 

[GuidoK]

You don't want to change the oil by removing the diff rear cover without removing the diff.
To install the cover again, you have to use rtv sealant; the original paper gasket is not available anymore.
And when reinstalling the diff, there is a chance that still some oil is leaking out over that sealant while installing, and that can cause leaks.
And if your diff leaks, you can do it all over again.
If you do it yourself it's no big deal, but if you're paying someone it sucks paying someone twice I imagine.
I dont even know if you can reach all the coverbolts with the diff in place.

I'd just do it with an oil suction device. Faster and safer.

 

[adam1985]

My 2007 3.0si manual doesnt have a drain plug so my indy used a suction tool to remove the old oil.

 

[cj10jeeper]

You don't want to change the oil by removing the diff rear cover without removing the diff.
To install the cover again, you have to use rtv sealant; the original paper gasket is not available anymore.
And when reinstalling the diff, there is a chance that still some oil is leaking out over that sealant while installing, and that can cause leaks.
And if your diff leaks, you can do it all over again.
If you do it yourself it's no big deal, but if you're paying someone it sucks paying someone twice I imagine.
I dont even know if you can reach all the coverbolts with the diff in place.

I'd just do it with an oil suction device. Faster and safer.

Pulling diff. covers off really is not an issue. I run comp Jeeps and drain both diffs after most 'wet' events. It's the only way to get all the oil out, check for metal frags. clean and refill. RTV is so quick and easy to use. 15 minute total end to end job, granted there's a lot of room to play with around rigid axle diffs.

In fairness though most Z4 diffs have a drain plug, so a 5 minute job to drain and refill