Which gearbox oil for 964RS?

[clarkey]

I'm very confused about which brand and type of oil I should put in my gearbox....I assume it is a non-synthetic, but what does everyone else use?

Thanks.

[dogsharks]

hello, and you may have seen my post on gear lube, etc.

I think you could benefit from using a good synthetic. Some Porsche transaxles use what is referred to as "yellow metal", meaning they have some brass or bronze parts inside. There is a "GL" spec that deals with the yellow metals, and all gear lube is therefore "GL" rated.

Mineral oil gets hot and the naturally occuring sulfur in the oil will react with the brass or bronze and cause it to corrode. Therefore you need to be sure to get a lube that has the right GL rating.

I like the Amsoil 75-90 which is available in the US it meets GL requirements #2 thorugh #5 inclusive. Mobil-1 synthetic gear lube, for instance, does not meet this same spec.

If you can get Red Line in the UK, it's a good choice, but I'm sure you have choices in UK that we can't get here, but I suspect the actual chemistry is very similar on both sides of the pond.

When I interviewed the factory tech, to be sure, he said the synthetics run so much cooler that you never really even get into the heat range where the yellow metals will be at risk.

When in doubt, call up the manufacturer's tech line and ask their R&D guy or their tech guy. Don't bother asking the sales staff, they're geared for the sale, if you know what I mean.

Good luck

Dogsharks "P"


1984 944
1983 928 5-sp
1990 944 S2
1974 TVR 2500-m
1966 38' Chris Craft, twin Ford 427's

[dogsharks]

here's a link that describes some of the synthetic choices you have. Note the "GL 5" reference.

all the best, Dogsharks "P"

www.pitstopusa.com/REDLINEGEAROILATF.asp

[ninemeister]

That's fine Dogshark but the 964RS has steel syncros, not bronze, i.e. there is no yellow metal in the box.

IMHO use non-synthetic HD75/W90 or 80/W90 and prevent your ring and pinion wearing out prematurely.

[dogsharks]

Neinmeister, so how is non synthetic going to keep steel from wearing more than a superior formulation with uniform molecules. I don't understand. The GL rating is just a sideline to watch for in the older cars, not a measure of wear resistance.

If you take the time to look at the AMSOIL web page, look at the "specs" for their 75W90 gear lube, and "read" their wear ball tests, etc. I don't understand how a synthetic with superior heat resistance and film strength will cause a tranny to wear prematurely.

What do you want to put up against my Amsoil or Red Line, I'll run you a friendly wager on this one. With best regards, Dogsharks

[domster]

Are you an AMSOIL dealer, dogsharks?

We can't get it in the UK, AFAIK, athough some Red Line products are available. But I have always felt these have a bit of a 'Max Power' image, and aren't given as much consideration as stuff from Mobil, Castrol etc.

Still, interesting stuff - if you're into how oil works . (I just put 10w60 Castrol RS or 15w50 Mobil 1 Motorsport in and hope for the best )

[ninemeister]

I am not a metallurgist or lubricant specialist dosgharks, I just replace worn out ring and pinions for people who are using synthetic oils in their gearboxes. Our gear manufacturer has the same opinion after seeing one on my bench. Lets just say that no-one will come running in with money to help you when your gearbox fails, all you will hear will be sorry....

[clarkey]

Redline recommend their (synthetic) 75W90 GL-5 with "friction modifiers for limited slip differentials". They insist that it is NOT too 'slippery' as many synthetics are.

I guess you recommend not using this, but getting a non-synthetic? I always used Redline in caterhams and it is good stuff, but....

[dogsharks]

I'm not a salesman, I'm an enthusiast (I'm an architect by trade).

Virtually everything I read suggests the engineered space-age synthetics are far superior to the old refined mineral oils. Every now and then I run across some old timer who is crowing about the old days, but guys, the new products ARE better.

Look over this, with regards to motor oils, and then figure the gear lubes are the same.

www.vtr.org/maintain/oil-overview.html

Hey, we're all in the enthusiast boat together, I have no reason for trying to sway someone to synthetics, other than I think it may help them run cooler and with less wear.

All the best,

Dogsharks, Nashville, TN

[dogsharks]

Here's the same article at a different link, in case that one isn't working for us today.

www.micapeak.com/info/oiled.html

Find the Mobil-1 products and see how superior they are to non synthetics, as a matter of fact, the 15W50 will flow down to colder temps than some 5-weight mineral oils. Need I say more? That's the difference between natural clumps of varying size molecules, and an engineered product with all the same size smaller molecules. Just better chemistry. Look at flash, VI, ash content, etc., and figure this is the same with the modern gear lubes. I happen to think Amsoil is amoung the best, but I'm sure "someone" must have an equal product, I'm just very impressed with how Amsoil tests out.

Dogsharks