Rennlist - Porsche Discussion Forums - 928 S2 manual gearbox into an S4

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928 S2 manual gearbox into an S4

Does anyone have any experience of converting a euro 928 S4 1987 auto to a manual. All of the manual parts I can get are from an 1983 S2.
i don’t want to buy the stuff if it won’t fit, so I’m hoping someone can tell me, and any other issues I’m likely to encounter? Tia.

I can only advise you what I uncovered when investigating such a project and decided it was just not worth the effort for me personally.

As I understand the earlier gearboxes are prone to wear of the synchros so mating with the S4 motor will not improve matters. Other than that I understand grafting such a unit into the S4 is distinctly possible even if it is not desirable compared to the later model gearboxes. If doing such I would also want a LSD diff unit in the transaxle.

Presumably you understand that what you are contemplating is no minor task, it has been done before and you will need to fit the plate that carries the clutch mechanism to the S4 body not to mention the pedal rail, slave cylinder etc etc.

Quote:

Originally Posted by backitoff (Post 15498557)

https://rennlist.com/how-tos/a/porsc...mission-384147
http://www.landsharkoz.com/tech/stu/conversion.htm

Hi Fred, thanks for the quick reply. I’m lucky that my car was specked with an LSD when ordered new, and I agree, is a great combo with the manual.
can you elaborate on the ‘plate that carries the clutch mechanism’ What I am possibly buying is ‘everything’ to convert includes pedals, flywheel, clutch, starter, slave cylinder, torque tube, etc etc. No mention of the plate you refer to though!
It’s a Porsche, in my experience of them, there’s no such thing as a simple task!

Great info! Thanks. Need to see about the bulkhead plate viability/sourcing. If I can’t locate that plate, do you think I could reinforce the area and fit a motorsport type master cylinder instead?

Quote:

Originally Posted by backitoff (Post 15498662)

928 International can [could?] do them when I enquired and now is an opportune moment while their annual half price sale is on if they have such currently available. Not the kind of part everyone is in a rush to purchase but necessary to do the conversion. The automatics were not built with this plate in situ given they do not need such. I understand it is a relatively easy part to affix. Not quite sure how to describe its function but I suspect it reinforces the bulkhead to resist the forces of one's hooves trying to put a hole in the floorboards- a mechanical leverage type of thing.

The piece of firewall is the mount for the clutch master cylinder which need only be riveted and glued over the new hole you cut in the existing automatic firewall. (yes Porsche had two chassis ) You also need to fit the smaller flywheel to the S-4 crankshaft but need it to be custom so it has the correct trigger wheel for the S-4 timing sensor....... that ring must be correctly indexed and tack welded in place.

Quote:

Originally Posted by James Bailey (Post 15499192)

Jim,

Is there some reason one cannot use the S4 manual flywheel with the correct ring?

would need the S-4 manual bell housing and complete late single disc clutch setup.....$$$$$

Quote:

Originally Posted by James Bailey (Post 15499480)

would need the S-4 manual bell housing and complete late single disc clutch setup.....$$$$$

OK- a logistical issue rather than a technical one.

I tell everyone the same exact thing:

"If you have a 928 with an automatic transmission and you really have to have a 928 with a manual transmission....sell your automatic and go buy a manual."