Front diff / Transfer case oil change.

[993turbo]

Im going to change the oil in my front diff/transfer case.

Any writeups on this? Where is the drain /fill plug?

Is it a combined front diff / transfer case oil?

I understand a LS oil is to be used.

Cheers!

[C6Dia]

Ive just had my gearbox oil changed by Chester transmissions. Really knowledgeable guys and very fairly priced.
Diy will undoubtably be cheaper but id save the hassle and get them to sort it

Edit** Just seen your location. Doh

[993turbo]

Haha, I do everything myself.

Anyway, just did the rear diff.

The rear diff has both a drain and a fill hole. Luxury. About a litre came out. 1,5l went in. Motul 300.

Now on to figure out the transfer case and front diff.

[C6Dia]

Haha, I do everything myself.

Anyway, just did the rear diff.

The rear diff has both a drain and a fill hole. Luxury. About a litre came out. 1,5l went in. Motul 300.

Now on to figure out the transfer case and front diff.

Happy days

[IanH755]

Zomeone with ELSAWIN access should be able to help you more but from what I remember when myself and TomRS were talking about this the front and "centre" diffs are both built into the gearbox, both only have fill holes (drain using suction via fill holes) and both need the "additive" oil which is different to the rear diff oil (motul 300ls vs motul 300 etc). I "think" there was seperate fill holes for each but I can't be 100% sure. IIRC the front diff fill hole was by the left driveshaft and the centre fill bole was by the prop shaft UJ.

[993turbo]

Yeah, located the fill holes for the front diff. Quite tricky to get to.

[douglas96]

Yeah, located the fill holes for the front diff. Quite tricky to get to.

Hi,

Did you manage to get both the transfer box and final drive drained and filled? Did you have to remove the tunnel crossmember and the gearbox support to be able to access the fill plug at the transfer box? I'm asking as I'm going to be changing the transfer box and final drive oils with Motul 300 LS next month. Elsa is showing that the fill plug is at the bottom of the transfer box and to get to it the crossmember and gearbox support have to be removed, whereas ETKA is showing it to be at the side of the housing. I know that the final drive fill plug is located next to the driveshaft so at least that's easy to get to.

Thanks,

Douglas

[douglas96]

I meant to update this sooner, but anyway here it is.

The rear diff is very easy to drain and replace - just make sure you remove the fill/inspection plug before draining it to make sure you can refill it. About 850ml or so came out and about 1.2 litres to fill it back up to level. I used part number YA745A from Snap On to fill the rear diff with Motul 300. I fitted new drain/fill plugs and torqued to spec.

Now onto the final drive and transfer box.

I had bought all of the necessary parts for me to remove the rear gearbox mounting so that I could extract and refill gear oil at the transfer box, however, after thinking about it I decided that I wouldn't bother doing this. The reason being is that the inspection/fill plug on the transfer box is 10mm in diameter. To try and get a pipe through that hole and to double back on itself to get to the oil, would be very difficult I think and even if If I did go to the bother of doing that, it would be a very small amount that would be extracted.

Since the transfer box and final drive share the same oil supply, I decided that I would extract oil from the final drive where access was the easiest, refill it to level with Motul 300 LS, drive the car so that the pump would circulate the oil around between the transfer box and then extract it and repeat this process a few times. Basically the old and new oils were being diluted - no different than when an oil change is done in the engine or the ATF is replaced in the gearbox.

Anyway, the oil that was extracted (about a litre or so at a time) was quite clean to begin with, however after the third time I could notice a slight green tinge to it (the Motul 300 LS is green in colour).

I used Snap On P/N VAC201 to extract the oil, and YA745A to refill the oil, ensuring that there was no leftover oil remaining inside it from when I filled the rear diff.

To remove and refit the fill/inspection plug on the final drive, I had to use an 8mm ball ended Allen bit socket. It must be ball ended because part of the subframe gets in the way otherwise. I used Gedore part number IN 30 LK 8 to remove and refit the inspection/fill plug.

There is still a slight smell of diff oil emanating from the car now when I park it up - some of the diff oil spilt on the subframe, and although I tried my best to clean it, a very small amount must remain.

Not a difficult job though.

[IanH755]

just make sure you remove the fill/inspection plug before draining it to make sure you can refill it.

The most important part of a great post there Douglas!!!

[Jim Haseltine]

There is still a slight smell of diff oil emanating from the car now when I park it up - some of the diff oil spilt on the subframe, and although I tried my best to clean it, a very small amount must remain.

It's my opinion that used gear oil (that's gearbox and/or diff oil) is the most revolting smell known to man. Back in my teens I spent around 6 months working in a mortuary and nothing I smelled during that time was anything like as pungent and malodorous as a tiny drop of gear oil.

[douglas96]

just make sure you remove the fill/inspection plug before draining it to make sure you can refill it.

The most important part of a great post there Douglas!!!

Yes! I've heard of a few people learning that the hard way! Fortunately I didn't have any bother taking them off, but just in case.

There is still a slight smell of diff oil emanating from the car now when I park it up - some of the diff oil spilt on the subframe, and although I tried my best to clean it, a very small amount must remain.

It's my opinion that used gear oil (that's gearbox and/or diff oil) is the most revolting smell known to man. Back in my teens I spent around 6 months working in a mortuary and nothing I smelled during that time was anything like as pungent and malodorous as a tiny drop of gear oil.

Haha, I agree it's not pleasant but I think the ATF for our gearboxes might actually be slightly worse!

I remember a while ago someone was demonstrating heat treatment of steel. He was heating a piece of mild steel to cherry red then quenching it in oil. The oil he was quenching it in was 80W-90 gear oil. I managed to accidentally breathe in some of the fumes from it and that was a terrible smell. I felt sick the whole afternoon after that!