Trans Lube Debate

cashflyer · 02-23-2007, 03:46 PM

I ran across this little item on a website. It's not the first time I've heard it said, and I am in no way trying to harm the website that this was copied from.

Quote:

All Porsche transmissions use a very steep hypoid angle in the differential due to the necessity of close shaft spacing. This is a very highly stressed item and requires the use of a GL-5 Specification gear Lube. Since these gearboxes all use the Porsche-design balk ring syncromesh, they depend upon some friction for these brake-band type syncro's to work properly. The best gear lube for a 901-915-930 transmission is the superb Swepco 201 gear oil. Using a synthetic gear oil in these transmissions will result in higher syncro wear and stiffer shift quality.

Anyway, here is my complaint.

I know Swepco is every Porsche mechanics "magic" curative, but I really believe that is just a function of "primacy learning". I don't see any mechanical reason that a properly rated synthetic should not be used.

And there are several synthetics that are GL-5 rated.

So... I would like to hear from people who really KNOW and have real experience (not people who have just heard a story from a friend). Especially if somebody like Lubemaster could chime in - or some other person who works in the lubricants industry.

I'm about to start a rebuild on my 915 in a week or so, and barring any real proof that I should not do so, I will be using a synthetic product such as this.

Thanks.

Jack Olsen · 02-23-2007, 07:42 PM

Geary, Wevoid, Lubemaster? Hello?

carrera · 02-23-2007, 08:19 PM

My 86 has 120,000 miles. 100,000 on synthetic lube and working very well. Shifts as well as my 88 with 30,000 miles. It seems that cars with worn 915's do poorly with syn, whilst a good 915 does well. I have been very happy with the syn lube particularly in cold weather.
I realize this is just one car, but perhaps others will speak up as well. As a side note, this car sees a fair amount of track duty.

SP2 · 02-23-2007, 09:40 PM

I am rebuilding my 915 tranny now. John Walker replaced all my shift sleeves, etc on my main and pinion shafts. He told me not to use Swepco for the first fill. Told me to use GL-5 rated 85-90 oil like Kendall. I think because of the break-in required to get it shifting smoothly.

Steve@Rennsport · 02-23-2007, 10:39 PM

Quote:

Originally posted by cashflyer
I ran across this little item on a website. It's not the first time I've heard it said, and I am in no way trying to harm the website that this was copied from.

Looks familiar,..

Quote:

cashflyer
Anyway, here is my complaint.

I know Swepco is every Porsche mechanics "magic" curative, but I really believe that is just a function of "primacy learning". I don't see any mechanical reason that a properly rated synthetic should not be used.

And there are several synthetics that are GL-5 rated.

So... I would like to hear from people who really KNOW and have real experience (not people who have just heard a story from a friend). Especially if somebody like Lubemaster could chime in - or some other person who works in the lubricants industry.

I'm about to start a rebuild on my 915 in a week or so, and barring any real proof that I should not do so, I will be using a synthetic product such as this.

Thanks.

IMHO, you should speak with several folks who actually rebuild-overhaul these transmissions so you get the straight info. This transcends lubrication experts who may not have seen the innards of these particular gearboxes over the years and observed the long-term effects of different oils (and owner techniques).

I will simply tell you that Porsche syncromesh (901-915-930 transmissions) work VERY differently than the common Borg-Warner syncromesh found in the vast majority of other cars including G-50 transmissions.

HarryD · 02-23-2007, 11:04 PM

FWIW, Grady Clay appears to have a most excellent discription of how the pre-G50 synchros work to give you an idea why the needs are different. See it here: Ever had to drive your car w/o a CLUTCH?

livi · 12:18 AM

Thanks for the link to Grady´s post.

That was truly excellent reading for a ignorant like me, frustrated from lack of understanding. Great mentor-ship Grady!

On the subject - I changed to Swepco 201 and have noticed one very significant change. First gear will now engage relatively easily. Before the lube change I frequently had to start of in second. Peculiarly, it took about 1000 miles after the change of lube before this effect started to kick in. Who can explain that ?

davidppp · 02-24-2007, 12:42 AM

Hello all.

The pasted original quote is plain wrong in at least one respect:

None of the early Porsche trans use a hypoind drive..the G50 is the first.

That said, the pinion is vulnerable to flaking etc..mainly IMHO realted to meshing going away when hot in the 901/911/914 and witha worn case or teddy bear in the 915....

Kind regards
David

Bill Verburg · Bill Verburg's Garage

There is no debate among folks that have btdt. The needs of the cwp on both 915 and g50 are the same API-GL5 or Mil-L 2105 B but the needs of the syncros are different. G50 works fine w/ synthetic, 915 needs Swepco.

I guarantee that if you use M1 in a 915 you will develop issues on fast shifts, it will come at the wrong time and may lead to other problems.

DanielDudley · 02-24-2007, 07:03 AM

Some synthetic manufacturers have created synthetics that are specifically designed to work with Porsche type syncros. It is made clear in their product descriptions. Swepco needs to be hot to work well, but then so does the engine. In any case you need a syncro specific lube, and there are several out there.

randywebb · 02-24-2007, 10:38 AM

Bill, cwp = ?

Bill Verburg · Bill Verburg's Garage

Quote:

Originally posted by randywebb
Bill, cwp = ?

crown wheel and pinion

cashflyer · 09:52 AM

I finally received a reply back from the Amsoil people and wanted to post it here as a follow-up.

Quote:

Harvey,

The Swepco 201 is just a regular petroleum gear lube with limited slip additives that meets both API GL-5 and MT-1. AMSOIL SVG 75W-90 also meets API GL-5 and MT-1 and contains limited slip additives. Both of them should work fine in your transmission. There are misconceptions lurking in the public such as the one that says don’t use a synthetic lubricant in some applications. The difference in petroleum and synthetic base oils are that synthetic will withstand more heat and resist oxidation longer than petroleum and synthetic will shift better in cold temperatures. Additives are what protect the gears, I’ll elaborate on that by saying to meet GL-5 it’s the sulfur phos additive that protects the extreme pressure (EP) caused by the sliding action of hypoid gears. AMSOIL puts an extra treat of EP additive in the SVG gear lube and should provide benefit beyond what is called for in your application.

Sincerely,

Kevin Dinwiddie
STLE/CLS
Technical Product Manager
Drivetrain and Power Transmissions
AMSOIL INC

Early_S_Man · 02-27-2007, 10:14 AM

That letter from Amsoil seems a bit disingenuous!

Besides the premium additive package that SWEPCO uses, including moly and other anti-wear additives, there is the additive that gives it superior adhesive/cohesive properties!

SWEPCO gear oils [I use 212, but they all do it] demonstrate that cohesive property that no other gear oil I have ever used exhibited. I am quite sure SWEPCO leaves a thicker, more tenacious film of oil on the gears when hot!

Geary · 02-27-2007, 10:45 AM

While the early Porsche R&Ps aren't hypoid, they are still a heavily stressed part requiring the finest oil available to deal with extreme pressure. This is why Porsche (and VW) have always specified hypoid gear oil.

The G50 & later hypoid Porsche R&Ps are much larger than the earlier non-hypoid parts... so despite their hypoid angles, they seem to tolerate synthetic oils better than the earlier R&Ps.

Our gear manufacturer has seen every type of oil used with his gears, and has relayed numerous horror stories involving the best known, high dollar synthetics. He has NEVER seen the same failures with high quality dino oil. So while oil companies continue to give glowing testament to their GL-5 synthetics, guys who have to deal with the reprecussions of early gear failures IN RACING USE tend to go with what they know protects internals best. You MAY never know the difference in your street car.

randywebb · 02-27-2007, 10:51 AM

Exactly - it avoids the entire point at issue - adhesion to the gears. Possible the marketing person or whomever it was misunderstood....

I am all for running experiments but since Swepco works just fine in my trans., I won't be experimenting with some other lube.

cashflyer · 10:55 AM

Quote:

Originally posted by Early_S_Man
That letter from Amsoil seems a bit disingenuous!

Well, it did come from an Amsoil employee....

I sent them my request for information within a few minutes of starting this thread. I just received the reply today and posted it.

Just to be clear, I am not trying to say that Swepco is bad. In almost every application, synthetic oils are touted as being superior - and echo what the Amsoil guy says (synthetic will withstand more heat and resist oxidation longer than petroleum).

I genuinely want to be sure that my 915 goes back together and is filled with the best fluid possible. Most of what I have seen in threads is anecdotal evidence and the old "I use it because it works".

Swepco may indeed be the best choice, but I still want to know why in this application a mineral oil is better than a synthetic. Is it strictly because of the brake-bands?

And if so, why does synthetic not screw up Dana Power Lok rear differentials - which rely on the friction of small clutch discs to provide the limited slip function?

Again - I'm not saying all you people are wrong. I'm saying, If I'm wrong then help me really understand why.

Edit: This was being written while Geary and Randy were responding.

cashflyer · 11:05 AM

Geary - mine is mostly a track car, which is why I am dogging this subject... because synthetics supposedly tolerate the high heat better.

Randy - I can't see that adhesion is an issue. The lower half of the entire trans is full of oil. The gears are spinning around in there at high rpm. I really doubt the upper gears are somehow deprived of oil. And how would Swepco stick to the gears any better than another oil? Flow is a function of viscosity, and in this case both oil viscosities are the same.

Would STP be even better, since it sticks to the gears better?
(okay... that was just being smart@ss)

cak · 02-27-2007, 11:00 AM

Quote:

why does synthetic not screw up Dana Power Lok rear differentials

There are special synthetic formulation for just that reason. Redline tacks on -NS (for No Slip) to signify that they're for that kind of diff, for example!

GM also makes (made?) an additive that can address this problem.

cashflyer · 02-27-2007, 11:10 AM

Quote:

Originally posted by cak
There are special synthetic formulation for just that reason. Redline tacks on -NS (for No Slip) to signify that they're for that kind of diff, for example!

GM also makes (made?) an additive that can address this problem.

The Swepco 201 and the Amsoil SVG both contain limited slip additives.

When using gear oils that do not have the additive, you are supposed to add the additive. Usually sold in 4oz bottles, I'm sure the GM product you mention is the same or similar to the MoPar product I used to use. However, you're not supposed to need it if the gear oil already has the stuff.