I am going to do the transmission fluid before I put the car away for the winter. I haven't seen any mention of changing fluid in the front diff. What's the deal? What oil, how much, how often, how do you do it?

thanks!

 

Sure - I change it when I change the transmission oil - which for me is annually. I buy the oil from Porsche - it's hydraulic (gear) oil 7W-90 - some folks use Mobil 1 or other stuff.

Very easy to change - same idea as the tranny. Drain plug on the bottom, the filler plug is on the right side. I usually run a tube with a funnel through the wheel well (tire removed). It takes 600ml to fill it (fill it slowly ). You should also change the washers for the drain/filler plug. Don't overtighten them - I believe it's supposed to by 17lb/ft. - I'll check tonight and let you know unless someone else can confirm in the meantime.

 

For a C4S with LSD, many use Mobil 1 75W-90 SHC for transmission and front diff oil. BTW, this is a different formulation from the Mobil 1 75W-90 found at your local auto parts store.

 

Enrico -thanks very much. I'll definitely add that to my "to do" list.

Eric - I made note of the SHC stuff in the archives. Mobil 1 doesn't have it on their website so I figured it was a discontinued product. I looked high and low in Ottawa just to find Mobil 1 75W90 ($20 per quart at the only place I could find it, versus $6 per quart for what is available at local auto parts stores). Looks like I could get a few gallons of the Mobil 1 SHC from that supplier for cheaper than what I paid. Hmmm. My car doesn't have LSD so I guess I would be OK with what I got.

 

Paul,
Your C4S should have LSD IIRC .... in any event, the Mobil SHC formulation has been relabled under the commercial "Delvac" line according to what I've read - at least in Canada. You can check out their link for more info.
If you find out where to buy it, drop me a line ....

 

[QUOTE=Garth S]Paul,
Your C4S should have LSD IIRC .... QUOTE]

Hey Garth! I remember checking option codes to see if I had LSD. Turned up negative. I guess you are suggesting (and I could maybe read that in to Eric's reply) that ALL C4S have LSD. My back wheels spin opposite direction when I spin one by hand when it is in the air. I thought this meant no LSD. Could it mean LSD broken?

I'll look around for the Delvec. In any case, the SHC could be had from the US at not too bad a price.

 

Paul,

Correction on the torque settings - I knew I had something wrong. Proper settings are:

Oil Filler Plug: 22Nm (16 ft/lb)
Oil Drain Plug: 30Nm (22 ft/lb)

I thought I read a TSB somewhere that updated those values but it may have been for the engine drain plugs. Anyhow - easy enough DIY - enjoy. Oh, and don't forget to check the magnet on the drain plug to see if you have any carvings

 

Taking a brief break to wipe off the sweat and calm my nerves. Not sure if anyone else has had issues removing the plugs for the trans and front diff. Mine were incredibly tight! Was able to remove both plugs from the trans but it took a cheater bar and tons of force - was worried they were going to strip. Now onto the front diff and same problem. However I cannot get the fill plug out and it is starting to round. Used penetrant and heat with no luck. Is this a common problem? These things are tighter than the SAI valve!

 

I know it doesn't need to be said, but I still will. Don't even try and remove drain plug until you get fill out. If it's not working, order new drain and fill plugs. Once you have them, take whatever steps to get the old ones out. You might try an oversized torx bit to get a bite in plug for removal, after you have new one. This is why I am glad, I'm the only one that touches my car. Good luck.

 

Yes that was good advice that I had read before. I did start with fill plugs first. Haven't tried the drain on the front diff yet. Going back out to the garage now for round 2.

 

No luck removing the fill plug on the front diff. The plug is now stripped. Hard to believe how tight that fitting must be. It doesn't look like there is a sealing washer under it like the drain plug and the two plugs on the trans - not sure if that is part of the problem, but either way this thing was torqued down way too hard. Tried to turn it using a chisel and pin punch but no luck. Looks like I am going to need to weld a fitting on to it. Cant think of anything else since you cannot grip the outside.

 

If you don't have a good set of torx, go buy a couple that are a little oversized. Just in case you break the first one. Pound that thing in there and make sure you're square on the wrench so you don't pry it out at an angle. Quick solid crack, pressure.
Or even try a set of the square ez outs, with the edge that catches inside a broken pipe.

 

This

 

Try as Overboosted suggested. If that doesn't work then JB WELD an Allen head socket in there

Edit: looks like we were thinking the same thing.

 

Or this. You may have to buy the biggest ez out, and then cut it back to the wide area that'll take up the rounded out hole.