Changing Transmission Oil

[blinkwatt]

How much has anyone paid for a transmission oil change on a 2.5L(manual of course)? Is this a DIY for a novice?

[MNBoxster]

Hi,

Easy DIY project. You'll need:

Parts:

• 17mm Allen Drive (for Fill Plug)
  
  16mm Triple Square, anti-tamer socket (or Hazlet 2567-16 12 Pt. Bit - .5" Drive - avail. on eBay or http://www.zdmak.com/wbstore/main.asp?action=PROD&PROD=HAZET256716&CTMP=1 ) (for Drain Plug).
  
  2.25 Ltrs. (2.4 US Quarts) SAE 75W90 Hypoid Gear Oil
  
  1 Stiff Piece of Mechanics Wire, or Coat Hanger w/ 1" bent to a 90° Angle

Procedure:

• Raise Car securely on proper Jack Stands
  
  Remove Plastic Splash Shield and Alloy Diagonal Braces
  
  Remove Fill Plug (17mm Allen Drive)
  
  Place Catch Container under Drain Plug and remove Drain Plug
  
  Clean both Fill and Drain Plugs
  
  Once Drained, replace Drain Plug - Torque to 25Nm (18 Ft./Lbs.)
  
  Add new Gear Oil through Fill Plug (Handpump and Tubing Helpful), about 2 Quarts.
  
  Then, insert Bent Wire, bend in downward orientation and pull back out, look for Oil level to be 11mm (7/16") below Fill Opening, keep adding Oil until this level is reached.
  
  Replace Fill Plug and Torque to 25Nm (18 Ft./Lbs.)

Differential shares the manual Transmission Oil supply, so no need to change or check level there.

Hope this helps...

Happy Motoring!... Jim'99

[Brucelee]

I am thinking Mobil 1 full syn gear oil 75W-90.

Jim?

[MNBoxster]

Originally Posted by Brucelee

I am thinking Mobil 1 full syn gear oil 75W-90.

Jim?

Hi,

You certainly could use Mobil 1, but the benefits probably don't outweigh the increased cost, and since it's rated GL-5, it may not be the best thing to use.

This is because Hypoid Gear Oil is used mainly for the Differential which uses Hypoid Cut Gears. Because of the sliding contact that Hypoid gears make, (Hypoid gear teeth appear twisted) , their Hydrodynamic Contact pressure is higher. To be suitable for use with Hypoid gears, a lubricant must be capable of resisting these higher pressures and is rated as EP.

A Manual Transmission won't usually contain Hypoid gears, so it
doesn't need an EP oil. But, in Transaxles (as in the Boxster) where the
Crownwheel and Gearbox share the same lubricant, Hypoid Gear Oil is needed.

Hypoid Gear Oils contain greater amounts of Sulphur or Sulphur/Phosphate compounds to withstand the higher Hydrodynamic Pressures and prevent Shearing. They have a typical Rotten Egg smell to them, especially after some service time.

One problem with these compounds is that they can chemically react with the parts in the Transmission, especially Yellow Metal Parts such as some Synchros and Bearings. I cannot find any information on the composition of the Tranny's internals, but if they are using any Brass, GL-5 Lubes can cause premature wear. This is why I would not use the Mobil 1. Instead, I'd go with a GL-4 Rated Hypoid Gear Oil - same Lubrication and Compressability qualities, but does not attack Yellow Metal Parts.

Mobil 1 touts their benefits as withstanding Higher Temps (not an issue here), Longevity (again, the Tranny is a sealed system and not subject to Dirt, Moisture which shorten the Lubricants Lifespan) and lower Viscosity (again, not an issue unless you're in Alaska, especially if you drive passively until the Gearbox has warmed up - which you should).

Personally, I just don't see the need and the fact that there could be some Brass in the Tranny causes some concern. It seems to me that possible accelerated wear to the Tranny and higher cost are real negatives. There are lots of GL-4 rated Lubes out there which will work just fine - I'm not sure there is a better in this case.

But, since the Tranny is sealed and unfiltered, it is prudent to change the Gear Oil every 3rd year to remove any of the metal shavings which will accumulate. Not more often because Gear Oil is actually better if a little aged - the Fresh Additives will not be especially good for it. Hope this helps...

Happy Motoring!... Jim'99

[JackG]

Redline MT-90 is a GL-4 rated 75W90 synthetic gear lube.

Royal Purple also has a Max-Gear synthetic that is GL-4/5 rated.

Both are claimed to not be corrosive to soft metals. Maybe these are possibilities?

[MNBoxster]

Originally Posted by JackG

Redline MT-90 is a GL-4 rated 75W90 synthetic gear lube.

Royal Purple also has a Max-Gear synthetic that is GL-4/5 rated.

Both are claimed to not be corrosive to soft metals. Maybe these are possibilities?

Hi,

They certainly could be. I have heard nothing but good things about the Royal Purple Line of products, and I use RedLine MT-90 in my Lotus Esprit.

The Lotus uses a Citroen SM Gearbox (modified), and it's really at the extreme of it's HP Rating in the Esprit. It uses Brass Synchros and so a GL-4 is called for. The Tranny shifts smoother and it is a must for any power-modded Esprit. In fact, Lotus introduced the Esprit SE because the Citroen Gearbox was no longer available and so they switched to a Renault Box which could take more HP, so Lotus redesigned the Head and aded a Chargecooler to up the HP to match the new Box.

If the Boxster uses hard metal synchros, there's no problem at all, but I've never been inside one and so cannot say for sure. But, GL-5 has been reported repeatedly to have attacked soft metal parts. GL-4 does not.

One other thing about the Synthetics is that they invariably make the Tranny noisier. This is because of their lower viscosity, and for some people, this may be a consideration.

I love synthetics, but not necessarily in every application. If the benefits cannot be utilized, it seems silly (to me at least) to pay a premium for the stuff. So long as the Oil level is kept at spec, a gearbox rarely fails because of the Oil it's using, except when Hypoid Lubes are used. Otherwise, most Lubes out there are really adequate. Gearboxes fail mostly because of consistent Operator Error...

Happy Motoring!... Jim'99
Happy Motoring!... Jim'99

[Cloudsurfer]

Resurecting an old thread here.... For a Boxster S 6-speed.... Is MT-90 a good choice? What else is worth considering? I'd prefer to stay with a synthetic due to the occasional use in the winter.

Patrick

[MNBoxster]

Originally Posted by bmwm750

Resurecting an old thread here.... For a Boxster S 6-speed.... Is MT-90 a good choice? What else is worth considering? I'd prefer to stay with a synthetic due to the occasional use in the winter.

Patrick

Hi,

You are not going to go wrong with RedLine MT-90. I've been using it for years in my Esprit, 240Z and my Race Car. It's really good stuff and you'll probably report better, more positive shifting and quieter operation. Obviously, this would be my choice...

Happy Motoring!... Jim'99

[John V]

I have had very good results with MT-90 over the years as well. However the Redline folks suggested to me that the best match for the Boxster S transaxle was their 75W90NS (non-slip) oil. I've had it in for about a year with no complaints. Some people, especially owners with B+M shifters, prefer the Redline "cocktail" which mixes the 75W90NS and Light Gear oil.

[Cloudsurfer]

Well, the MT-90 is a GL-4 fluid, while the 75W90 is a GL-5. The question then, obviously, is does the 6-speed box in the S have any yellow metal in it to worry about?

Patrick

[CJ_Boxster]

Dont forget you have to remove the metal rock sheild under the tranny and you will need a Pry bar to get the diagonal braces and rock shield to pop off.

[roadracer311]

Speaking of pry bars... Has anyone had trouble getting the plate and braces to line up when going back on?

[blinkwatt]

Originally Posted by roadracer311

Speaking of pry bars... Has anyone had trouble getting the plate and braces to line up when going back on?

Yeah I did. Just talk your palms and push the darn thing up as hard as you can. It should go on.

[saaber]

Originally Posted by MNBoxster

Hi,

They certainly could be. I have heard nothing but good things about the Royal Purple Line of products, and I use RedLine MT-90 in my Lotus Esprit.

The Lotus uses a Citroen SM Gearbox (modified), and it's really at the extreme of it's HP Rating in the Esprit. It uses Brass Synchros and so a GL-4 is called for. The Tranny shifts smoother and it is a must for any power-modded Esprit. In fact, Lotus introduced the Esprit SE because the Citroen Gearbox was no longer available and so they switched to a Renault Box which could take more HP, so Lotus redesigned the Head and aded a Chargecooler to up the HP to match the new Box.

If the Boxster uses hard metal synchros, there's no problem at all, but I've never been inside one and so cannot say for sure. But, GL-5 has been reported repeatedly to have attacked soft metal parts. GL-4 does not.

One other thing about the Synthetics is that they invariably make the Tranny noisier. This is because of their lower viscosity, and for some people, this may be a consideration.

I love synthetics, but not necessarily in every application. If the benefits cannot be utilized, it seems silly (to me at least) to pay a premium for the stuff. So long as the Oil level is kept at spec, a gearbox rarely fails because of the Oil it's using, except when Hypoid Lubes are used. Otherwise, most Lubes out there are really adequate. Gearboxes fail mostly because of consistent Operator Error...

Happy Motoring!... Jim'99
Happy Motoring!... Jim'99

This has probably been answered elsewhere but if someone is searching this may help... In regards to GL4/GL5 and is their Yellow metal in there Qs, I got some good info From Doug H. at Renntech re original tranny oil FYI. This was in regards to an 00' S

"...perhaps the initial fill was an Esso product
Mobil are emphatic about specifying their "PTX" lubricant or going to a Dealer and Castrol (Germany) recommend their excellent SAF-XO (at 160k kms OCI)

In any case they all concur on a 75w-90 synthetic (GL5) but not all gear oils are made the same and the above two are recommended with good purpose and no doubt to improve shift quality and longevity

Many Manufacturers do have special gear oil "brews" and in many cases these are only available via the Approved Dealers"

Also, if you don't want to go through all the hassle of removing the plates underneath, you can use a $6 hand pump and pump out the old fluid via the fill hole. On the 00' S the fill hole is on the drivers side and is a 10mm. You don't have to remove anything this way but you will only get about 1.75 liters out, leaving about 1/2 liter of the old stuff, so it is great for refreshing but probably doesn't replace the 90k recommended drain and fill.

[HammerESQ]

Bumping this thread again... Is the gear oil capacity, and filling instructions the same for the 6 Speed in the Boxster S, and the 5 speed in the regular Boxster?

Thanks,
Eric

[insite]

Originally Posted by MNBoxster

One problem with these compounds is that they can chemically react with the parts in the Transmission, especially Yellow Metal Parts such as some Synchros and Bearings. I cannot find any information on the composition of the Tranny's internals, but if they are using any Brass, GL-5 Lubes can cause premature wear. This is why I would not use the Mobil 1. Instead, I'd go with a GL-4 Rated Hypoid Gear Oil - same Lubrication and Compressability qualities, but does not attack Yellow Metal Parts.

helpful post. FYI, i had the opportunity to look inside a 986 5-speed this week. the synchros are indeed brass.

[blinkwatt]

Anyone here used Redline MT-90 with a 6-spd gearbox? If so how was it?

[jaykay]

Is royal purple gear lube (GL-5) okay with "yellow metals"? I am putting this in an 00 S 6-speed.....brass synchros???

[jaykay]

............bump

[JFP in PA]

As you might expect, Porsche uses a totally unique spec full synthetic gear oil. Gear oil manufacturers, the honest ones anyways, admit that they do not have a compatible lube. Mobil 1 sent me an email in response to one of my customers questions on the subject, stating : “Currently, Mobil 1 does not produce a gear lubricant suitable for Porsche applications.” Other manufacturers have been less forthcoming in what they say.

Perhaps more interesting, we have switched several cars back to the OEM product after they had been using Red Line, RP, Amsoil and other “blends”; the common response has been, “Wow, it shifts much better…..” Considering what these gearboxes cost, and the fact the OEM stuff is not expensive, why bother?