dustinsc

Hello! I've been using the advice on this forum for more than a year, and it has been supremely useful! This is my first post, for something I haven't been able to find an answer for:

I just changed the front and rear differential fluids on my 2005 CTT (160k miles). I changed the fluids when cold. Based or recommendations on this site and others, I used mobile 1 75w90 gear oil. Two issues that I'm concerned/wondering about:

1. On the front differential, I opened the fill plug first, and maybe 6-8 oz of fluid came out. This concerned me because I can only fill it until it starts to spill out.

2. Front and rear capacities are 1.1 qt and 1.5 qt = 2.6 qt total for both. I ended up being able to put in only 1.75 qts. total between front and back - I have 1.25 qts. left of the 3 qts I purchased. I'm concerned that both diffs are now low on oil.

I didn't jack the car up - I just put it in the highest suspension mode, so I assume that the car was level.
Should I have done this with the diffs up to temperature? Similar to how I had to do with the auto transmission fluid? I've not seen any instructions to that effect on my searching through the forums and on the web.

I suppose that I'll try to top front and rear off again, now that I've put a few miles on it, but I'm not terribly confident that anything will be different.

Any thoughts or suggestions?

BlackTurboS

When I did this to my diffs in 2015 on my 09 Turbo S I had the same concern. I was only able to get a little under a quart in the front diff and a little under a qt in the rear diff as well. I was told my a Porsche tech friend that there may be more fluid in diffs from the factory than what you would replace it with during a change, but the amount required is to fill until it runs out the fill plug.

I filled as much as I could until it started running out, and never topped off. I'm 20k miles in now and both diffs are quieter and running smooth.

As a note, I had a whine noise from my front differential, changing the fluid didn't fix it. I replaced the fluid again last year with the recommended gear oil but mixed in some LucasOil heavy duty gear oil. Whine went away - bought my some more time until I replace the whole front diff..

Best of luck... sounds like you are fine if you filled as much as you could. I wouldn't worry about it.

dustinsc

Thank you very much, BlackTurboS. The fact that someone else had the same experience makes me feel more confident.

Dilberto

Those are correct capacities - fill until it spillls...cap it and done.

malimt

Greetings guys,

I saw this thread and I felt compelled to get involved. When is it required to change the Differential Oils? I'm at 60k miles now and thankfully not experiencing anything unusual with the Diff. However, I thought I should ask to get a general idea of when would be the right time to change mine?

Would really appreciate some advice here.
Thanks.

kino1161

What is the process for changing or adding fluid to the differential? How do I know if I should ADD or CHANGE the fluid?

08 GTS

dcapper

Remember. The diffs are splash type fluid setup. Not like the engine oil. If you were to somehow fill the diff right full, you'd blow your seals. I did my diffs and the same thing, a few hundred ml came out.

dcapper

https://www.pelicanparts.com/techart...Oil_Change.htm

https://www.pelicanparts.com/techart...Oil_Change.htm

It's a simple job, but getting at the fill plugs are hard. I used a torx bit on a wrench. Remember if you are going to do it, make sure you can get the fill plug loose before taking out the drain plug and draining the fluid. You'll need a fluid pump. I used a cheap one from Harbor Freight or Princess Auto. Can't remember.

kino1161

JAGMAN1

Fill until it comes out the top hole.

kino1161

Great. Thank you.

Mega Man

As as with any fluid change you want the recommended amount which in this case is to the "fill plug hole" level. You should never be concerned with how much came out because how do you know the last idiot didn't put too little or too much or that some fluid has been lost over the years or level has increased due to moisture? Always put the recommended amount no matter what comes out... That goes for any fluid.

Pillow

See the DIY DAN videos on YT.
https://www.youtube.com/playlist?lis...A9J2apL0l2q-q0

Also there is a stubby allen key available.

FCP Euro also has kits for the diff/trans case/transmission.

kino1161

Thanks all!

VicS

Quick update to this older thread as I'm changing out fluids:

Rear Diff, PTY specific fluid, 000-043-305-03 (now supersedes 043-300-37)
Front Diff. fluid 000-043-305-04 (now supersedes 000-043-205-30)