Manual Trans gear oil recommendation

[mrpcar]

Hi guys,

This is my first post, the guys on the Porsche board couldn't really give me a straight answer so I thought I turn here for help.


I have a 1999 Porsche 911 Carrera 4 (4 wheel drive model) so far knock on wood everything seems to be in working order except some minor crappy loose interior trim noise, minor exhaust rattling sound and the way the transmission shifts, especially when it is cold. It is almost impossible to shift to first gear unless the car is stopped completely for few seconds when cold, and very notchy going to 2nd. Once the car is fully warmed up it is buttery smooth. So I want to change the transmission gear oil to see if it would make any difference.

After checking with Porsche related web site I have gathered some information but still couldn't answer all my questions.

This is what I know so far:

(1). I need to use oil that will protect both the differential and provide enough friction for the synchros to work since the transmission/differential unit in the 911 is a combined unit in design (Thus share the same fluid)

(2). Mobilube PTX (synthetic) 75W-90 GL-4, GL-5 is what the factory recommends. The GL-4 rating supposely provides enough friction needed for the synchros to work properly, and the GL-5 provides protection for the differential under high pressure environment. So the gear oil needs both the GL-4 and GL5 rating and mix.

(3). Can't get Mobil PTX here unless you want to pay outrageous price from the dealer.

(4). I was told that the Front tranaxle uses the same oil as the transmission GL4/5. (On a C4) Just curious of the construction component of the front transaxle if using GL4/5 would be suited. As the factory shop manual states using ATF fluid, which was later found to be a typo.

(5). Someone recommended using Silkolene Silktran SYN 5 API GL4/5 75W/90 as a substitute, which is available in the US for $15 / liter. Have anyone tried this?

(6). What oil recommendations do you guys have?

Just curious if I am on the right track?

The shop manual is also not too clear on this subject, so I want to ask the board to see if anyone can shine a light on this subject.

TIA

Robin

 

[02StangGT4Foam]

mrpcar,
Nice car!! I checked the Amsoil site (www.amsoil.com and click the RED button in the bottom middle) for you and they recommend Severe Gear 75W-90 for the Manual Trans, and both front and rear diffs. That is probably the best oil on the market (IMO). I should be getting my most recent order tomorrow. Hope this helps.

 

[mrpcar]

02Stang,

Thanks for your reply. I din't say it meets the GL4 standard, but it however does say it can be used in GL4 application... I wonder about this.

Sorry to be so picky, don't want to ruin a $4k tranny... LOL!

 

[02StangGT4Foam]

doesn't the GL-5 standard encompass the GL-4 standard also. I think Amsoil is saying that this "newer" standard also meets the "older" standard. Not sure though.

 

[mrpcar]

That's the confusing part. I was under the impression that GL4 basically is needed for the friction of the synchro, and the GL5 is for the prection of differential under extreme pressure conditions.

If I just GL5 approved oil then it is too slippery for the synchros to work properly, if just GL4 then my differential may fall apart...

Maybe I am way off here....

 

[Pablo]

Rest assured the SVG will work fine in the tranny and protect the diffs.

 

[par]

I would try the Amsoil SVG. If it feels and shifts good (and I strongly suspect it will), then it will not damage the syncros. Also, it has the protection of the GL-5 rating.

I have been using the Amsoil Series 2000 in my tacoma for several years and I tried them all (literally) and found this was the best.

 

[MolaKule]

quote:

---

That's the confusing part. I was under the impression that GL4 basically is needed for the friction of the synchro, and the GL5 is for the prection of differential under extreme pressure conditions.

---

The GLX rating as a rule of thumb apllies to the EP protection for the gearing and has nothing to do with the friction modification for the synchros.

Our MTL-R is a 75W90 with a dual rating and has the correct FM for synchro assemblies.

I would recommend our HDS-5 in 75W90 for the rear axle or differential.

quote:

---

I was told that the Front tranaxle uses the same oil as the transmission GL4/5.

---

If it is a single transmission/axle assembly in one unit, then it is a transaxle and uses the same fluid.

This drive train is similar to some Subaru's.

 

[Titan]

MolaKule wrote: If it is a single transmission/axle assembly in one unit, then it is a transaxle and uses the same fluid.

This drive train is similar to some Subaru's.


I have one of those Subaru setups, SF MTL-R shifts MUCH better than the Factory lubricant.

 

[Bror Jace]

Yes, I'm currently using the slightly lighter SF MTL-P in my Nissan 6-speed. Great stuff, worked better than either of the Red Line syncromesh fluids.

If the manual calls for a GL4/GL5 75W-90, Specialty Formulations MTL-R would be at the top of my list.

mrpcar, I have to know ... what is the dealership charging for what they claim is the 'proper' oil? More than $20 per quart?

02StangGT4Foam: "Doesn't the GL-5 standard encompass the GL-4 standard also? I think ... this 'newer' standard also meets the 'older' standard."

Absolutely not. Using a 'GL5 only' rated oil in a GL4 application is taking a chance that the GL5 additive package (and there are a few different ones out there) may damage the transmission. It's not the risk it was a decade or more ago but there's still some risk ... and why chance it with so many great fluids currently available?

--- Bror Jace

 

[HEV]

Looks like Molakule is on vacation for a few days (hey, we all need it sometimes). Mrpcar. Let us know how it works out. Trust us on this, you will not find anybody here more knowledgeable than Molakule. And, he is such a standup guy, if he doesn’t have a formulation for you that will work for you, he will recommend one from a top notch competitor.

 

[mrpcar]

Thanks for all of you guys's help. I will post result once the DIY is complete.

BTW. Unrelated question. Porsche factory engine oil fill recommends using 0w40, so I use the Mobil 1 0w40. Is there another alternative synthetic oil that you guys would reommend? And how much a quart?

TIA

 

[Titan]

Before someone else suggests it, how about GC 0-30? It's almost a 40 weight, and some say it thickens with age (I don't know this for a fact, mind you). Also, check the thickness of the Mobile 1 0-40...it may be on the thin side of a 40 weight. I think it all depends on how hard you actually run the engine and the resultant oil temperature, since the oil temperature affects the oil viscosity so much. Dr. A.E. Haas' musings on this subject are good to read...might make you seriously consider GC 0-30.

 

[Bror Jace]

mrpcar, being in California where it is not particularly cool, you could use just about any high-quality XW-40 oil: 0W-40 (the Mobil 1 you already know about), 5W-40 (lots of good choices here), 10W-40 and 15W-40.

--- Bror Jace

 

[02StangGT4Foam]

don't forget about Amsoil Series 2000 0W-30 http://www.amsoil.com/storefront/tso.aspx or Amsoil Synthetic 5W-40 European Motor Oil http://www.amsoil.com/storefront/afl.aspx

 

[mrpcar]

They make you buy 20 liter of the Mobilube PTX in one shot... $550!!!!


Looks like MTL-R 75W90 is the way to go for me.

Thanks for the input guys.

BTW. Specialtyformulation's web site is down?

 

[HEV]

Yeah, I'll also recommend the Amsoil 5W-40 European Motor Oil. I think it lists for 6.85 a quart. The other oil that might be fun to check out is the Mobil 1 5W-40 Truck and SUV oil. Ignore the Truck and SUV part, it is plenty suitable for use in a car. It's a robust, heavy duty oil. With the Amsoil you can get it for 5.20 a quart as a preferred customer. A certain site sponsor from the Pacific Northwest may also have some shipping incentives...

 

[michaelc80]

I tried Amsoil SG 75W90 in my 2005 Subaru Outback manual transmission, and quite honestly didn't care for it. It was extremely hard to shift when cold (although it was great when the transmission was warmed up). It did seem to take several miles before it would begin to shift smoothly. There would be times when I nearly couldn't get it into first gear until the transmission was warm.

After 2 weeks changed again to Redline 75W90 and the difference is amazing. It might be slightly stiff at really cold temps (10 or less) until it's run a mile or two, but still easy to shift and none of the "notchy" feeling. Feels good when it's warmed up as well.

I'm an Amsoil fan and run it in everything else I own, but for some reason my Subaru manual transmission didn't like it.

 

[scoobdude]

I own a 2004 wrx and have the same feeling of the amsoil. To improve the shifting, i dropped a qt of the amsoil and added some penzoil synchomesh so i could shift again. Subaru trannies are notarious for (especially the wrx) for the hard to get into 1st gear and 1st gear grind.

Although i don't like to mix oils, in this case its the only solution as the penzoil is GL-4 and the amsoil is GL-5. Good luck and keep us posted.

also you tranny may be similiar to a subaru's, but its in the back (i think)

 

[peterr]

MrPcar

Stylin' Ride. I love the 996. My next Pcar will either be a used 996 C4 or a Cayman depending on how resale prices go in the next few years.

I assume that you tried Rennlist? That is the best Porsche board out there. I am on my third Porsche and it is a really good reference.

If your car specs 75w90 I would try what MolaKule recommends, the Specialty formulations MTL-R. I just replaced the fluid in my winter car (Mazda MX-3) with this as it calls for a 75w90 GL4/GL5.

My 1988 Porsche 944 Turbo is running Redline fluid which seems to be popular in the Pcar aftermarket community. That fluid was installed by the PO about a year ago and only has about 5000 miles on it and the specs are different due to the combined trans/diff, so I have not seen the need to change it out. As with many things automotive it is also difficult to translate older factory recommendations into todays' real offerings. For my 951 I have seen original specs for "SAE 80 Hypoid Oil meeting GL4/GL5" and "80w140 hypoid gear oil" but that was written almost 20 years ago.