jphughan

I've been looking around for this info and have been coming up short, which surprises me considering that this is the same transmission that's been used on the 981 for years already. I've seen a pretty consistent recommendation to change it every 10K miles on cars that see track time (Porsche's guidelines specify every 120K -- quite a difference!), but I haven't found any DIYs. It seems there are several 75W-90 oil options out there, but they're not all the same (or even all appropriate) and it's not clear which one is OEM. I also haven't been able to find how much oil the transaxle assembly takes, whether the protocol is to fill it until it spills out of the fill hole or only to a prescribed level below that hole as measured with a paperclip, or even whether there are any single-use bolts, crush washers, seals, gaskets, etc that should be replaced. I even tried emailing Suncoast and they didn't have this information. Does anybody have any guidance here? Or does anyone with access to Porsche's servicing guidelines want to take a look at what it says for this?

Bill Lehman

I believe the standard fill is Mobil 1. I use Redline. These mid-engine cars suffer from lack of cooling at the trans. I changed the trans oil in my 987 every year. I did about 9 events a year. It takes about 4 qts. to fill. You're supposed to leave the level slightly below the fill plug. I filled till it ran out. I'm pretty sure there is a DIY article over on the Cayman Register. No single use parts.

jphughan

Thanks! Do you have a specific Mobil 1 or Red Line product? Suncoast lists just "Manual Transmission Oil" ($40/liter), Mobil 1 MobiLube ($40/liter), and then Mobil 1 Delvac ($40/gallon), all 75W-90, and I think Red Line has multiple versions with different friction modifier packages. I know some are specifically for or specifically NOT for LSDs, for example. The Delvac looks particularly tempting because Suncoast says it's standard fill for Cup cars and is apparently 1/4 of the cost of the others. But good to know that roughly 4 qts would be required -- thanks again!

okie981

Are you wanting to do this solely for preventative maintenance or are you seeking to change the way the gearbox handles some shifts like the 1-2 upshift? Several people on this forum have reported occasional synchro or gear grind during 1-2 upshifts. Curious if anyone has experimented with gearbox fluids with friction modifiers that can modify synchro behavior.

jphughan

Purely for maintenance reasons. I've got a ways to go before 10K miles, but I wanted to be prepared. I had that grind early on a few times but haven't experienced it again in I don't know how long (I've got 3800 miles now), and others have said the same.

Jenner

I just researched this same thing yesterday since I will be hitting the suggested "mileage" for a car that does DE events (1 DE event = 2500 miles change trans fluid every 15,000 miles and my 6th DE will be on Monday).

Everything I read from all the Porsche big transmission guys pointed to using only DELVAC with a stock LSD and to NOT use any LSD modifiers and to not use Redline.

How to/DIY Guide here:
http://www.caymanregister.org/showthread.php?t=33549

Great info from Matt here (posts 36 & 41):
http://www.renntrack.com/forums/show...ange-DIY/page3

Even more info here:
https://rennlist.com/forums/996-gt2-...l-for-gt3.html

HTH.

jphughan

Great info! Although unless you go to some amazing DEs, one DE should not be 2500 miles -- was that 250? And fwiw, GTgears in the thread asking about whether a break-in transmission oil change should be performed said that that wasn't necessary and that it should be changed after half a dozen track weekends, not days, which works out to about every 10K total miles for me anyway.

EDIT: Just saw that GTgears was the one who wrote the posts on Renntrack. If he says use Delvac on cars with an LSD as long as it's changed frequently, that's good enough for me.

Jenner

I might put 250 TRACK miles on my GT4 in a single DE BUT 250 miles on the track is much harsher than 250 miles on the street. Thus 1 track day is the equivalent of 2500 street miles.

This is what I read in that thread (bolds are mine):
Matt Monson = GTGears...

jphughan

Ah ok, didn't realize that you were comparing DE wear and tear to equivalent street mileage. That's strange to see Matt saying 4 DEs there because here's the thread where he says half a dozen weekends tops between gearbox oil changes: https://rennlist.com/forums/gt4/9027...in-1k-too.html.

GrantG

Is there a site where this is posted that doesn't require PCA membership?

A432

Have tried them all and agree with this 100%.
Synchros work better, downside is you will get a little more LSD groan in tight low speed turns (like a parking situation) due to less FM.
Also like the fact that you can feel the LSD working better, use the DELVAC w/o FM, change every 4-6 events depending on heat/duty.

jphughan

Wonderful, thanks! Nice to know that the least expensive option is the right way to go, and the ability to buy a single gallon jug to cover the whole job rather than 4 liter/quart bottles is a nice added bonus.

Jenner

If you are a member on Planet 9 they have a PDF version you can download:

http://www.planet-9.com/reviews/serv...r-removal.html

Direct link to download (you need to be signed in):
http://www.planet-9.com/downloads.ph...d=379&act=down

RocketGuy3

Holy hell, Porsche recommends changing the transmission fluid ever 15K miles!?!?

Is it just me or... is that kind of a lot???

I'm new to the manual transmission world (bought a manual S550 GT about 1.5 years ago), but I know my auto cars didn't need near that much care.

Jenner

Pretty certain Porsche doesn't expect you to ever change it (certainly not during the warranty period) and considers it a "lifetime" fluid (or perhaps change @ 108,000 miles) for street use.

Most people who bought a GT4 don't use it for street use ONLY...YMMV