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Question - the reason, in my head, that a 6spd is attractive, was to use 6th as an overdrive gear for the street. Is that feasible on the 5 spd? Meaning, primary gears for street/track use are 2-3-4. For me, most track I go on (I rarely go to Fontucky) are 2-3-4, top speed at 120 or so ( need to look at my 964 data again, but roughly... Buttonwillow, chuckwalla, streets of willow, occasional thunderhill which is higher speed). I just don't want to cruise at 4k RPM in 5th :-)
Also, it's NOT a race car obviously, but a dual purpose toy
Question - the reason, in my head, that a 6spd is attractive, was to use 6th as an overdrive gear for the street. Is that feasible on the 5 spd? Meaning, primary gears for street/track use are 2-3-4. For me, most track I go on (I rarely go to Fontucky) are 2-3-4, top speed at 120 or so ( need to look at my 964 data again, but roughly... Buttonwillow, chuckwalla, streets of willow, occasional thunderhill which is higher speed). I just don't want to cruise at 4k RPM in 5th :-)
Also, it's NOT a race car obviously, but a dual purpose toy
There are some minor variations to 5spd based on year, but those are the 964 ratios. You can see you get NO gain with a 6spd until 4th gear unless you regear it. I just looked and the package we are doing for SW is:
3.154, 2.176, 1.526, 1.174, and stock 5th. Top speed in 4th is around 125-130mph. It is intended for a toy car, not a race car. You can do it without changing the mainshaft if you prefer and just leave it at 3.500.
There are reasons to go go w/ either a 5 or 6 speed.
Stock g50/03 is well suited for stockish 964 motor and chassis, much better suited than a 964/05 or the latter 993 g50/20
But the 993 g50 21, g50/3x trans have their own allure, especially so w/ a modified motor.
Here's a stock 964 /03 compared to a stock 964 /05 compared to a stock 993 /20
Same only the /20 is replaced w/ a /30 from a 993Cup
the /3x have all sorts of internal upgrades, from bearing to shift forks to steel syncros w/ , teeth that have angles more conducive to positive shifts, none of the parts are cheap
it was my understanding that only /10 used in 964 RS/Cup used steel syncros, maybe I understood wrong but the literature does seem to make an issue of the /10 steel syncros an different tooth angles on them fo 1 -4
it was my understanding that only /10 used in 964 RS/Cup used steel syncros, maybe I understood wrong but the literature does seem to make an issue of the /10 steel syncros an different tooth angles on them fo 1 -4
This is correct. we stock the RS steels for 1-2. When you are looking at under $400 for one, it's a relative bargain compared to the $1800 steels for a 993 2nd. 3-5 steels are the same as 993/GT3.
Also, all 5spd gearboxes got a steel 3-4 shift fork similar to the one used in the G50/3x 6spd boxes. It's only the G50/2x variants that use brass. None of the 5spds got brass.
This is correct. we stock the RS steels for 1-2. When you are looking at under $400 for one, it's a relative bargain compared to the $1800 steels for a 993 2nd. 3-5 steels are the same as 993/GT3.
Also, all 5spd gearboxes got a steel 3-4 shift fork similar to the one used in the G50/3x 6spd boxes. It's only the G50/2x variants that use brass. None of the 5spds got brass.
Yeah, that's because the 993 uses a double cone synchromesh on 1 & 2, the rest are the same single cone design used in 964
the double cone is a nicer design, don't know that it's 2x a nice though the 6 speeds also have that nice oiling supply for the 3 & 4 loose gears w/ the fixed 3 & 4 in a permanent bath due to the extra pan bolted to the tensioning plate
unless he finds a /3x or one that's been done right he will need to update a lot of internal parts in either transmission.
Call me crazy but a 6 speed done right has it all over a 5 speed done right just because of the closer gearing. Add the possibility of a wider range to the mix w/o compromising spacing and you have a winner.
Expensive though
My Motorsport 2nd gear syncro was less than $1000 on my 6 speed build.
The reason I decided on the 6 speed was because I didn’t want to lower 5th (highway) or raise 1st (stop and start traffic) but still wanted closer ratios. Also I wanted a lower 2nd for passing on 2 lane roads. I didn’t see a good way to regear the 5 speed- its just about right as it is for street use in my case.
I decided to go with the same 1st as the 5 speed (3.50) and similar gear as 5th for 6th(0.857 factory cup.) At Suzuka there are several corners that I felt I had to compromise on- either 2nd and run out of steam or 3rd and start under the power curve- and now I’ll have a better choice for each of those types of corners. Overall the rpm drops only change a few hundred rpms per shift but the flexibility is definitely something I’m looking forward to.
Honestly though if I knew what I was getting into I might of just stuck with the stock 5 speed. I already purchased the 6 speed and had it at Bill Rader’s when I figured out that the stock 5 speed ratios were better than the stock G64/51(converted nose cone etc to 2wd box) for my intended use. It was all or none and I just went for it. No regrets! Bill came up with a used mainshaft and that made the decision a little easier. It’s definitely going to be a fun box- just going to have to wait on any other major mods for a while while the wallet recovers.
I used an app called Shift RPM to look as gear ratio’s as well as an excel file provided by Bill. The app shows the ideal shift points i.e. where the next gear surpasses the current gear in terms of power output. I also used Blocklayer as well as a spreadsheet provided by Bill to educate myself and make my final decision. Here is the chart from Shift Rpm showing my ratios as an example:
Yeah. contact Bill. He's got Alex's gearbox waiting from him when he gets back from Werks Reunion.
To the above post, steel synchros in 2nd are a good upgrade, but they still don't protect how delicate the little dog teeth are. And more importantly, you can't change the ratio because it's stuck on the main.
got quote from bill for the above. Not cheap but less than i thought for 1-4 plus needed bearings and steel synchro.
08-24-2018, 12:04 PM
