G8620-103 (03 Boxster S 6-speed) manual transmission and LSD flush

[serialize]

Hello, I'm looking for some guidance please.

Apologies for creating a new manual transmission flush thread.
I'm read through hundreds and pages of material regarding this and its all very good information.
I'm just left a little confused when it comes to my Boxster specifically, because I believe I have the LSD limited slip differential because of the PSM in my car. I was specifically not looking to get the model with PSM but when I was recently shopping for my used Boxster this one was the best overall condition, mileage, and least owners, just ticked all the other boxes.

I have some service history for the car, but nothing indicates the transmission oil being flushed or the diff (if there even is one??). My transmission code is G8620-103 and based on other posts, this should be the one with LSD.

So my question is, will I be flushing and filling 2 separate units, one for the gearbox and one for the differential?

Also, my biggest concern after reading for days about this topic, what fluid and what capacity for each:
Gearbox oil type and capacity?
Differential oil type and capacity?

I know the 2 oils to use are Shell Spirax S5 75W-90 and Mobil 1 Mobilube PTX 75W-90

We can't get either here in Canada, and the Porsche dealers (all of them, I called them all) say to use Porsche Classic GL-5 oil, but reading through all the research material this car will require GL-4 only due to corrosion to the brass internals. Has anyone else with the 6-speed and LSD gone this route like what the dealer is recommending?

Sunset Porsche online retailer is one of the rare ones that will ship to Canada and I can only get the Mobil 1 Mobilube PTX 75W-90 from them, but sounds like that is one of the original formulations that went into these cars so I'm fine with that and will be ordering, I just don't know if should only order 3 liters for the manual transmission or if I should order more to have enough to fill the LSD as well?

I would really like to flush and fill the manual transmission on this car since I don't think it has ever been done, I also plan to change the front motor mount and flush the coolant while doing that.

Thank you so much for any feedback and guidance on this.

[The Radium King]

you don't have an lsd - the psm is electronic (uses the abs to control traction).

the boxster uses a 'transaxle' which is a combined transmission and differential - flushing as per the pelican how-to does both. you will need 3 litres of fluid.

https://www.pelicanparts.com/techarticles/Boxster_Tech/38-TRANS-Manual_Fluid/38-TRANS-Manual_Fluid.htm

note pelican will also sell you the fluid ...

and pro tip - take out the fill plug first. you brick your car if you drain the fluid only to find out you can't get the fill plug out.

otherwise pretty much everyone will tell you to use the porsche fluid. i've used a variety of 75w90 fluids including motul and redline with no issues. if you want to do more searching, the porsche 996 uses the same 6-speed transmission and a lot more info out there for the 996. i think you'll find that the gl-4/gl-5 discussion is a bit moot since most of the high-end gl-5 gear oils have been engineered to no longer corrode the yellow metals in the transmission.

[serialize]

Originally Posted by The Radium King

you don't have an lsd - the psm is electronic (uses the abs to control traction).

the boxster uses a 'transaxle' which is a combined transmission and differential - flushing as per the pelican how-to does both. you will need 3 litres of fluid.

https://www.pelicanparts.com/techarticles/Boxster_Tech/38-TRANS-Manual_Fluid/38-TRANS-Manual_Fluid.htm

note pelican will also sell you the fluid ...

and pro tip - take out the fill plug first. you brick your car if you drain the fluid only to find out you can't get the fill plug out.

otherwise pretty much everyone will tell you to use the porsche fluid. i've used a variety of 75w90 fluids including motul and redline with no issues. if you want to do more searching, the porsche 996 uses the same 6-speed transmission and a lot more info out there for the 996. i think you'll find that the gl-4/gl-5 discussion is a bit moot since most of the high-end gl-5 gear oils have been engineered to no longer corrode the yellow metals in the transmission.

Hey The Radium King, thank you so much for this reply and info.
This is really great info and super helpful.
I was thinking along the lines that maybe the gearbox and diff are combined since noone actually talks about filling the diff separately so thank you for clarifying. Also great to hear no LSD, I don't want that since I want a very traditional roadster which is why I bought this car. I don't even like the PSM and doing all the research on how to jumper it to disconnect but without throwing all the codes.

Great to hear about the Motul, coincidentally the main guy around here "the Indy" told me that he mostly uses Motul as well and no issues.

Since I'm a super OCD car owner and so by the book as in what the manual says, what should I do for oil? I don't mind paying all the extra to get the original GL4 porsche oil, happy to pay more for the original formulation. Or should I go with what the GL5 dealer stuff is being pushed now?

The one at Sunset is this one:
MobiLube PTX 75W 90 - Porsche (000-043-210-12-SP)
https://www.********************************************** **************************.com/p-mobilube-ptx-75w-90-4321012sp

I can call Pelican and see about the one that actually comes in the porsche bottle (the original GL4 formulation), but I think when I called them they said they won't ship oil cross border so I might have to go with the Mobil 1 Mobilube PTX.

Thanks again for the quick and informative The Radium King, really appreciate it!!

[serialize]

Originally Posted by The Radium King

you don't have an lsd - the psm is electronic (uses the abs to control traction).

the boxster uses a 'transaxle' which is a combined transmission and differential - flushing as per the pelican how-to does both. you will need 3 litres of fluid.

https://www.pelicanparts.com/techarticles/Boxster_Tech/38-TRANS-Manual_Fluid/38-TRANS-Manual_Fluid.htm

note pelican will also sell you the fluid ...

and pro tip - take out the fill plug first. you brick your car if you drain the fluid only to find out you can't get the fill plug out.

otherwise pretty much everyone will tell you to use the porsche fluid. i've used a variety of 75w90 fluids including motul and redline with no issues. if you want to do more searching, the porsche 996 uses the same 6-speed transmission and a lot more info out there for the 996. i think you'll find that the gl-4/gl-5 discussion is a bit moot since most of the high-end gl-5 gear oils have been engineered to no longer corrode the yellow metals in the transmission.

Thank you very much for the reply The Radium King.
This is super helpful and informative, and this helped me decide to get the original Porsche fluid GL-4 formulation. Turns out Pelican will ship it to Canada. $268 for 3 liters, but hey its I'm transmission and why take chances.