CAGCTG

I am considering a rebuild of the transmission in my '97 Carrera. Along with that, I was interested in replacing the brass sychro rings with steel ones that were used in the Carrera RS. Does anyone have experience with this? Will this allow faster or smoother shifting?
Thanks

'97 Carrera Coupe Arctic Silver, Chestnut interior
'13 Carrera S Coupe Aqua Blue Metallic
'17 Macan S
'57 Corvette (!)

Bill Verburg

Yes to both of your questions, it's expensive but worth it, besides the material change there is a tooth angle change on the syncros, from 110° to 120° this sucks the parts together w/ more authority

1-2 & 3-4 are 3 piece deals and are very costly, the rest aren't that bad

I'd also replace the shift forks w/ something more robust, GT used to have them but I don't know that they are still available

CAGCTG

Thanks Bill. It gives me confidence to go forward (and spend the $$)

pp000830

It is unlikely that all your gears need new synchro rings.

Jupiterfish

i have the same concerns, my 2nd pops out if i load it hard.

Jupiterfish

what are the prices you are getting to do this, i need to do the same next.

Gbos1

I rebuilt and regeared to the 993 GT Transmission Specs including Steel Synchros, Shift Forks and lots of other stuff while in there. Cha-Ching!!!!! Good luck!!!

CAGCTG

My local Porsche mechanic uses California Motor Sports in Lake Havasu. I don't know the cost.

AZ993

Sorry for pursuing this tangent, but... What are the ratios for the GT spec? I have read Bill’s posts on the G50/30, /31 and /32 ratios but never came across a GT spec. Curious if you changed mainshaft as well.

I’ve been contemplating a regear as well and acquired a lightly used set of GT gears with ratios of 1.5, 1.227, 1.04 and 0.867. I was wondering about brass vs steel...

When I emailed CMS it was mentioned that unless track times >30 min sessions, likely would do just fine with brass synchros. Although aside from cost, I have not read any downsides from going with steel synchros.

To OP, are you regearing as well or just freshening it up?

Gbos1

Honestly I would have to dig up my paperwork. I gave him full reign on the rebuild. My Indy worked with G-Box out in Colorado. One of the best in the Porsche Transmission rebuild business.

https://www.gboxweb.com/

nsully

When I dropped my tranny at 78K I decided to get it out to Brian Copans for a refresh.
I wasn't experiencing any issues but thought it was a good idea. (isn't everything we do to our cars a good idea...)
Also wanted to upgrade to a Motorsports LSD so it was an easy decision.
He did replace the synchros with steel as well as the upgraded shift fork mentioned earlier.
Good Luck!
Neil

replaced parts

Bill Verburg

the other thing to replace idf the car is tracked is the bearing, stock has plastic cages that fall apart quickly when tracked
here's some of the debris pulled from a friends

pp000830

For street use can anyone here speak to why the OE synchros look to be a bronze or brass alloy, softer than steel as the standard material for the synchros?
My thinking is that why would Porsche not use steel parts as the default for synchros if there was no downside in doing so and durability would be improved?
Could the trade-off be that synchros' friction rings have a longer service life when mated to soft metal verses the harder steel?
The service life of tens of thousands of miles is important on street driven cars vs racing where the transmission may be subject to being opened up and served regularly, the transmission is subject harsh conditions in primary use and an occasional miss-shift at extremes of operation may be encountered..
Andy

Bill Verburg

Some combination of cost & feel

dragon993

how much would a rebuild cost for a 964 gearbox to rebuilt to RS specs, synchros and gears?