Over the nine years of owning my '96 C4 6-MT I have gone deep into the regear question several times yet never pulled the trigger... but will most likely one day. Nonetheless, having scoured the innumerable great RL threads on this topic many, many times before, today, I'm still confused by the gearbox serial number...

I am close to putting in an offer on a '95 C2 w/factory LSD option code M220. The GB is stamped "G5020 2 000890", which falls well below the 02174 changeover number (woohoo! loose 2nd) that B. Verburg has graciously posted here many times before. What has me stumped is the PET decoding diagram describes the serial as 5 digits yet shows an allowable range of six digit numbers 002001>999999, which is also how the box is stamped. I assume "2" for LSD is Porsche's definition of a "variant". My interpretation is that the LOWEST a serial number can be is 2001. What am I missing? ...and please confirm to me this should have the coveted mainshaft with only integral 1st.


Edited to remove the pic's that didn't post as images but tonnnnnnns of text...

 

Hi Logenbrew,
Chart
Andy

 

That's interesting.

The only other 993 trans i've seen w/ a 3 digit serial # is Cup and RSR /30 & /34, my guess is that is avery early maybe even '94 despite what PET lists

the 2 after the /20 is a street asymmetric lsd, Cup and RSR will have a 4 there for the motorsports version lsd

it's not an AWD trans as that would have g64 ******

 

@loganbrew , even if the trans turns out NOT to have a separable 2nd gear, all is not lost - Guard Transmission / Matt Monson @GTgears makes a custom mainshaft for the G50. I used Matt’s mainshaft in 2014/2015 to net a 3.500 1st gear and 2.294 2nd gear. Note that a 3.500 1st gear allows for even less of a ginormous 1st-2nd rpm drop than the Porsche <02174 mainshaft with the integral 3.818 1st gear.

That said, I do not know the state of availability for the GT mainshaft in 2023.

 

Thank you gents, both for your responses today and your many contributions on the re-gear topic before.

I ended up reaching my limit on the car $1500 before the BaT winning bid today, so kind of a moot point now.
https://bringatrailer.com/listing/19...rera-coupe-47/
I would have gone higher, but I was less than impressed that the otherwise stellar 3.8 build had reused the original slip-fit cylinders bored to 102mm.

@pp000830 I tried to post the same diagram/chart in my original message, but encountered technical issues during submission. But notice how the top diagram describes 11 specific digits, yet there are 12 stamped on the box and, as shown in your second chart/table, there are 12 digits one page below in the PET? That's doesn't make sense.

 

In the sellers auction he stated it was standard gearing. I was also able to confirm standard /20 gearing in the driving videos he posted rowing through the gears with both tach and speedo visible

This is what I was envisioning based on the purported 300 WHP.

 

gearing desired depends more on the torque curve and RPM limit

Here are most of the n/a 993 trans overlayed, all have the same 3.8 RS engine for comparison purposes, they don't look all that different but the difference between a /20 and /21 is night and day as is the difference between a /21 and /30

 

Exactly. Not having a torque curve I extrapolated the 3.8's torque based on sellers purported peak 380 BHP relative to (what I believe is) a stock 3.6 dyno. My simulator includes inputs for shift points, but redline at each shift is generally optimum.