924 tech specs reference thread

althejazzman · **Posted:** Tue Sep 22, 2020 1:53 pm

Lesworth wrote:

CedricN wrote:

Lesworth wrote:

924 Turbo Gear Oil spec is missing: SAE 80 GL4.

G31 924 turbo boxes have GL5 in the factory documentation.

Interesting....my factory manual says GL4 and specifically not to use GL5!

I also read in several places on this forum to use GL4 and not GL5 as it is not compatible with some of the alloys in the G31 box.

CedricN · **Posted:** Tue Sep 22, 2020 2:54 pm

althejazzman wrote:

Lesworth wrote:

CedricN wrote:

Lesworth wrote:

924 Turbo Gear Oil spec is missing: SAE 80 GL4.

G31 924 turbo boxes have GL5 in the factory documentation.

Interesting....my factory manual says GL4 and specifically not to use GL5!

I also read in several places on this forum to use GL4 and not GL5 as it is not compatible with some of the alloys in the G31 box.

Ive seen it in other forums aswell, but the factory manuals are pretty clear on this point, so I will trust those! :)

Lesworth · **Posted:** Tue Sep 22, 2020 3:43 pm

CedricN wrote:

Ive seen it in other forums aswell, but the factory manuals are pretty clear on this point, so I will trust those! :)

Mines a factory service manual too! :?:

scm924s · **Posted:** Tue Sep 22, 2020 3:51 pm

1981 Turbo Specification from factory brochure.

scm924s · **Posted:** Tue Sep 22, 2020 4:04 pm

Lubricants also specified here (GL5 for gearbox)

http://www.924gt.com/924techspecs.pdf

All of which probably adds confusion!

Lesworth · **Posted:** Wed Sep 23, 2020 8:26 am

I went back and double checked and I was looking at the wrong section. Agreed that GL5 is specified for the turbo in my manual also.

althejazzman · **Posted:** Wed Sep 23, 2020 9:45 am

Have I "done it wrong" then with my recent gearbox oil change?

Lesworth · **Posted:** Wed Sep 23, 2020 10:03 am

Pretty sure I have GL4 in mine too Alex. I'm doing a complete fluid change over the winter so will be swapping it out for GL5

scm924s · **Posted:** Wed Sep 23, 2020 11:05 am

Having established that GL5 is the manufacturers recommendation in 1980/81 for Turbo's, I think you guys need to establish whether this is still appropriate in todays market. Oils have changed dramatically over 40 years, many more additives are included, possibly better, possibly not. The original concerns over increased sulphur content in GL5 vs GL4 were that this increases the corrosive attack on yellow metals in the syncros and bearings (GL5 was listed as not suitable for syncromesh gearboxes unless recommended by the manufacturer- which Porsche had done in our case).

I think you need to speak to a known gearbox repairer (some of you have had them reconditioned) and check what Porsche recommends (probably not helpful as they just recommend their own fluids).

GL5 was recommended as it offered better protection for the extreme pressure the transmission incurred due to higher performance.

Maybe a bit of research is required?

Carrera RSR · **Posted:** Wed Sep 23, 2020 6:38 pm

I've only ever used 75w90 GL5. Its what's also recommended with Quaife LSD's which has been in my boxes.

Just looked at the Porsche Technical Specification document and GL5 is listed for all boxes?? I'd seen various threads on using GL4 and just ignored them and took reference to the Tech Spec doc.

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