gobble

I've had really good luck with Red Line oils and would like to change the transaxle oil in my girlfriend's 2005 6 speed Boxster. Red Line recommends their 75W90 NS gear oil. Has anyone tried it?

Marine Blue

A while back I exchanged emails with one of the top aftermarket transmission and LSD suppliers regarding transmission maintenance intervals and fluids. The exact recommendation for the 987 is as follows:

While you see a lot of debates about the "best" gear oil and I usually stay out of them, I will make one comment on your gearbox. Your car uses a carbon lined synchro that is not used in any other gearbox aside from the Cayman. Porsche has gone to great lengths to develop a gear oil that is specifically designed for that gearbox. No matter what the jury of the internet tells you, never put anything but the factory Cayman/Boxster gear oil in there. And ignore Porsche's service interval. At the most, change your gear oil every 15k mi for street use and every 2500 miles for track use.

I'm not sure if anything has changed for the 981 gearbox, hopefully someone can chime in to confirm.

BostonDuce

Not to be disrespectful to my former homeboy Afshin and his source, but the Honda AP2 S2000 had carbon syncros back in '04.

I can personally guarantee that non-oem ******* has performed flawlessly in one of those gearboxes for the better part of 10 years, with improved cold shifting and reduced gear clash over the OEM recommendation (Sorry, not looking to start "my oil is better than your oil" war).

Just what does "OEM" mean when is comes to fluids? There is NO manufacturer that is brewing up their own fluids. They all source it from someone else, with the deciding dynamic most often being $$.

As always, YMMV.

BD

PS. This is not an endorsement to use WD-40 in one's transmission.

Marine Blue

Nothing wrong with a healthy debate. I might try to get my source to post here to confirm since this information came from him.

It would also be interesting to know if the OP is experiencing any shifting issues which led to the question about trying to find something better.

gobble

No shifting issues. It just time and the Red Line is easier to get because I'm stopping at Pegasus for a few other Red Line products.

A432

As a data point, TPC racing uses 50/50 Redline 75-90 NS and 75-90 to get the right friction coefficient for synchro operation and wear.

gobble

Interesting

orthojoe

FWIW, I swapped to redline 75-90 NS after 12,000 miles. The OEM fluid looked fine even with heavy track use. The redline fluid seems to work just fine. I can't tell a difference between OEM and redline, but I wasn't expecting to.

Bill Lehman

When I added a Guard LSD, Bodymotion used Red Line 75/90.

GTgears

The only change to the 981 gearbox is the addition of a cooler.

Redline MT and NS are acceptable gear oils. I wouldn't put shockproof in my worst enemy's gearbox. It is a horrible excuse for a gear oil.

I stand by my original statement. I would only put the factory fill in a Cayman. That's based on 3 seasons of Grand Am racing with BGB and our experience with those cars. People can do what they want to do like I said in that email I don't argue about it. You can take my opinion fwiw. I don't care if you agree or not. I have no vested interest in any particular gear oil and as long as there is an Internet guys will yell back and forth about the "best" oil.

gobble

If you were to do Red Line, would you do MT90 which is GL4 or NS which is GL5? Caveat that this for a Boxster, which is a girl's car, not a race car.

GTgears

NS.

Some street guys like the MT because it's more slippery and easier to shift when cold. Personally I would never use it. The way some people get around the GL4 versus GL5 rating is they mix the NS and MT and think that's adequate. I figure if the formula isn't right from the factory, I'm not going to be able to make it better by mixing and matching. Not something I would ever suggest doing though you see it mentioned multiple times in other subforums on this board.

gobble

Since you seem to know so much about gear oils, any thoughts about what Red Line oil I should be putting in the transaxle and front differential of my 04 Gallardo? The factory fill is Agip Rotra LSX 75W90 oil they list as GL4+GL5. It's hard to get in the states.

Most people seem to be using MT90 or MTL, but that's a GL4 and my read of the Agip oil is GL5.

Appreciate your insight.

GTgears

Can't say that I know anything about that particular gearbox. I'd hate to guess.

That said what I consider the best (and one of the more expensive gear oils in the States) is something called Synolac from a blender in Texas call Lubrication Engineers. You have to buy it in a 5 gallon pail. However the Race teams I know who use it see upwards of a 20 degree drop in gearbox temps. It's the real deal.

gobble

It's just odd because the factory gear oil is GL4+GL5. I've never seen that before and don't know if it's a GL4 that also meets GL5 specs or a GL5 that also meets GL4 specs.