unique

I am running a 3.2 in my carrera. Its a stock 3.2 with no other mods. I was considering long tube headers/exhaust and tune. I dont care for the power because its enough. I do care about the transmission because as a driver, the gears are too long for me. I need shorter gears and a rebuild because my tranny is already due for one, on top of that an LSD. Any recommendations as to gear ratios and ect for a 3.2 with a nice LSD set up. I will be doing more street driving with the car because I have dedicated track cars, but I will take it on the track here and there, so the quafe is not my cup of tea from the readings I have searched here on RL.

Thanks for the info guys

Bill Verburg

for the lsd GT 40/60 is hard to beat

as for the gearing a stock '74 Carrera has a 915/06 which you can find here in this table, not too many stock trans w/ shorter gearing. This is already a pretty short box



One of the sweetest 915s i've ever driven was a 915/71 in an SCRS
It looks like this when limited to 6800rpm


and like this w/ a more realistic 7400rpm shift points

unique

Bill,

Awesome post, thank you so much.

From the looks of it I will upgrade to an 8:31 3.875

unique

http://www.gboxweb.com/915specs.html

if you scroll down you can see it. What do you think about the 915/40?

Bill Verburg

If you change a 7:31 to an 8:31 you are making the gearing taller not shorter

unique

doh, lol

My mistake. So what do you think I should do?

rusnak

It sounds sort of like you should just leave the car alone. Not sure what "due" for a transmission rebuild means

Bill Verburg

I dunno it all depends on what you want and what compromises you are willing to put up w/

An option on the SCRS was a trans that would limit top speed to ~125mph in 5th which is ~4k @ 74mph on the highway

I like the 8:31 cwp because it's stronger and more durable than a 7:31
the SCSRS std gearing w 6800 rpm w/ the same rear tires compared to what you have gives(tires will cause more variation too)
SCRS ~39 63 91 116 141
yours ~34 60 87 118 151

The taller lower gears move them closer to the shorter upper gears which means for a shorter drop between gears, the shorter drop to a point is what most people really want, the SCRS also has the stronger 8:31


torque curve enters here too, a stock 3.2 doesn't normally rev to 6800

unique

the transmission just feels sluggish, it grinds from 1st to 2nd occasionally.

I drive my cars hard when I drive them and want something fresh so I can confidently use as a tool. I have competed in professional racing series before. imsa mazda prototype lites cooper tires. They are like large go karts with sequential transmissions and **** load of down force. I also compete in shifter karts currently s-1, which is the pro class.

So behind the wheel I am heavy and enjoy the drive.

I have spotted out after only owning my 74 carrera for 3 months that the weak point is the transmission and the gears. After speaking with many owners, my ability to tell the cars weak point was dead on. I have heard from owners that changing gear ratios on these things is a game changer in driving stand point. I came to this conclusion by first driving the car and confirmed my hypothesis by asking around.

thanks for telling me not to touch my tranny. Nothing can ever be broken, it can only be changed and fixed, I might end up doing 4 different set ups for my tranny until i get what I want. So in consideration to myself, its my own money to burn however i like.

unique

My local shop, is called tre motorsports, they know what they are doing.

They recommended keeping my 1st gear the same, and shortening 2,3,4, and leaving 5th gear the same, so I can have a highway gear. they said they can do this with 8:31

I will post details Bill. Thanks for your input man, your awesome!

GTgears

unique,
The thing you have to realize with the 1-2 shift is that most people do not rev the engine up enough before making that shift. The sweetspot for that shift, given the large gap, is 4000-4500rpm. That will go in pretty easily with a bare minimum of involvement from the synchros.

As for regearing, just be aware that aftermarket gears make more noise than stock. Might not matter to you, but I always like to point that out. More than one person has gone through this whole process, gotten their car back and hated the sound of the gear whine.

Regards,

Matt

Bill Verburg

They do have a good rep
It almost sounds like it's the shifting that is you issue, the 915 will never shift like a modern Japanese trans. The shifting can be greatly improved by adding shift components from Wevo, don't forget to use one of their shift couplers too. Or the trans could just be tired and need a freshening up.

I really dislike the kind of trans you describe, I'd try to drive one before spending the $. It sounds like they are recommending something like this


to me it's the worst of all worlds w/ a big drop from 1 to 2 and 2 to 3 and then another big one from 4-5

JCP911S

All the info you need here... big question is to be very objective on exactly how you plan to use the car.

For example, my 78 SC is a PCA stock race car. The 7:31 pinion is popular as it is legal as a "Prepared" mod. Changing the gears move you to a GT class, so this is an artificial constraint. People also go to 15 inch tires for the same reason... not that it is better, just that it fits the rules.

For a race car, 1st gear is only used to get around the pits, never on the track. 5th is an "overdrive" and totally useless on the track.

For a street/performance car, a taller 1st with closer 2-4, and maintaining stock 5th for highway is a logical approach... completely different driving environment.

Changing gears is IMHO, the most cost effective way to improve real-world acceleration on these cars, but you must be very objective on how you personally plan to use the car.