Capt. Obvious

Time for everyone's favorite discussion: drivetrain fluids!

The shifting in my '99 is a bit notchy going into 2nd and it's almost to 90k miles, so it's due for a change anyway. I tried searching but couldn't find the info I was looking for.

Does Porsche recommend a different transmission fluid for cars with a limited slip differential?

I know a lot of people recommend Mobile Delvac 75-90, but does that have the friction modifiers that an LSD needs?

Or, if the fluid is different from the standard Porsche fluid (part number 999.917.546.00), does anyone have the part number for it?


Update for people searching in the future: Cars with the factory LSD use the same fluid as the non-LSD cars if you're using Porsche-approved fluid.

MiamiC70

Interested too as my 2004 40th AE also has a LSD.

D6lc

i changed mine on my 40th, with the Porsche fluid from Suncoast, it was expensive and I didnt notice any improvement in the shifting. Hoping there is a better option out there for teh next oild change

alpine003

I changed the fluid too since it was notchy and even after that, there wasn't really any improvement. You should also try tweaking your settings on your shift cables. It made a noticeable difference for me(especially when cold). Even with the factory alignment tool, your adjustments can be off a couple MM from optimal position. Even factory original shifters might benefit from tweaking the shift cable adjustments.

Capt. Obvious

I'm installing my 997 SSK this weekend, so I'll be playing with the adjustment this weekend. I don't know if/when the tranny fluid has been changed before, so I still want to change it anyway.

On a high note with the sloppy 2nd gear, it's just notchy and not popping out of gear, so I have that going for me.

Macster

None of the official Porsche sources I have mention anything about any friction modifiers for LSD. For manual transmissions there are just two fluids approved for use. A Mobil fluid and a Shell fluid.

If you have an aftermarket LSD in the diff then the LSD maker may have its own recommendations regarding fluid and you should probably follow that recommendation.

Also, I have found a fluid change can improve shifting feel most noticeably when the transmission is warmed up at the expense of a bit more reluctance shifting when cold. This is quite acceptable to me, as smooth fast shifting is a must have when the car/tranny is warned up. The cold shifting is not that bad. After a few blocks of driving the shifting improves some and before I know it the tranny is warm enough shifting is just fine.

Another thing that can improve shifting is a good brake and clutch fluid flush/bleed. If it has been nearly 2 years or more since you last did this you should consider doing this before fiddling with the shift linkage adjustment, but after you change the transmission fluid.

Capt. Obvious

It's the factory LSD.

996Ray

Hi Capt,

I went through this a couple of months ago. I have the Porsche LSD as well. I could not find any documentation that requires a different fluid for our transmissions. If I knew about Suncoast at the time I would have ordered the Porsche stuff. That being said, after looking at the different posts on Rennlist, I tried Delvac. For me, it was nearly unusable cold. It was fine warm, but, 2nd and 3rd cold was awful. So, more searching. I saw some really positive write ups about Motul 300. I got it locally and it worked great!!!

If you can order Porsche fluid from Suncoast or if you have a local Porsche dealer, I would put in the factory stuff. Though my tranni feels great....Motul 300 is not approved by Porsche.

jrgordonsenior

Friction modifiers are NOT for use with a clutch type LSD which is what you have (same with Guard). Designed to help the synchros and gears, it also affects the ability of the clutches in the LSD to work. Friction modifiers may be guilty of some shifting issues because the synchros do in fact need some friction to function properly....

In my race car I use a special fluid from Lubrication Engineers that both Matt @ Guard and Viking on this board have recommended to me. No tranny or diff issue with this fluid which is designed to work in sub- zero temps. Linked below is their 75-90 which is perfect for street applications. They also make a 75-140 which is what I race on...

http://products.lelubricants.com/ite..._utmk=64170607

Capt. Obvious

I swung by my local Porsche dealer (Barrier Porsche in Bellevue, WA) and asked about the tranny fluid. They said the same fluid should be used whether or not the car has the factory LSD. Also, they only had fluid in the big container, but were willing to sell it by the quart if you bring your own container.

keytohwy

What'd they charge for a quart?

fpb111

I tried Mobil Delvac very hard shift when cold.

Motul 300 Works perfectly for me.
Motul Racing GEAR 300 75W90 - 100% Synthetic Ester

GermanCarSpecialists

This can get into a heated debated.

heligear

I used a product from millersoils.co.uk their products are highly rated.

knfeparty

SWEPCO 201 has "limited slip characteristics" so I have used that for a couple of fills now. It shifts great warm and on the track, but when it gets cold (and by that I mean below 70 degrees) it gets really difficult to shift. I wouldn't recommend it if you live somewhere that is regularly below 50 where you store your car. Unless the Porsche fluid becomes easier to buy, I'm going to stick with the Swepco.