Transmission Poll

[KEISLER]

Originally Posted by Sieg

Mini thread-jack

Shafi,

Are you going to have an all inclusive kit for us 67-69 Camaro/Firebird people that can't stand the embarassment of their automatic muscle car?

My goal is to get my '69 somewhat track day competent. Current 3:73 posi with Moser axles, 355 ci, 202 heads, GM "Duntov" cam, 650 Speed Demon, that comes to life around 3-3,500 rpm. Will the RS-5 600 close ratio gearing be a decent choice?

I had the car 21 years now and it's about time to increase her fun factor.

Indeed! Check out the complete solution HERE. I've attached a pic also.

Sounds like the Duntov cam is similar to the one used in the 327ci/365HP Corvette '63-67. I had a '65 Vette with this engine, and it liked to run above 3000rpm also. This motor will work exceptionally well with the RS500 deeper first gear. Those engines like to rev and can use the extra torque multiplication the lower first gear provides. That being said, the 2.80 first gear will motivate the car with less torque multiplication, but less drop in the 1-2. If you shift at 6500rpm, you'll be going 40mph with the RS400/500 and 48mph with the RS600.

Check out a really nice gear speed calculator here. Use the ratios to compare the two for your application.

[Sieg]

Originally Posted by KEISLER

Indeed! Check out the complete solution HERE. I've attached a pic also.

Sounds like the Duntov cam is similar to the one used in the 327ci/365HP Corvette '63-67. I had a '65 Vette with this engine, and it liked to run above 3000rpm also. This motor will work exceptionally well with the RS500 deeper first gear. Those engines like to rev and can use the extra torque multiplication the lower first gear provides. That being said, the 2.80 first gear will motivate the car with less torque multiplication, but less drop in the 1-2. If you shift at 6500rpm, you'll be going 40mph with the RS400/500 and 48mph with the RS600.

Check out a really nice gear speed calculator here. Use the ratios to compare the two for your application.

Thanks! I also have the 327/365 Vette heads. Appreciate the gearing input, most vehicles I've had, including bikes have typically had too low a 1st gear, lighting the tires or running out of rpm too soon, making short-shifting to 2nd the norm. Feathering the clutch a little adds to the experience. I don't place much emphasis on city driving with the car as I'm in a small town, country roads is where I enjoy it. With 3:55's it could see the taller 1st being a problem, with 3:73's I'm on the edge in your opinion?

Sorry for the jack Ron, hopefully you get some info from the input.

[Ron Fox]

Thanks Keisler and Sieg. Keep the information coming. The more I hear the more I learn.

The RS 5-speed sounds like a good, all around choice. How many have been sold to this point?

Are there any guys here running the RS 5-speed?

[Sieg]

Originally Posted by Ron Fox

The RS 5-speed sounds like a good, all around choice.

Are there any guys here running the RS 5-speed?

+1

[Sandbagger]

Originally Posted by Sieg

Thanks! I also have the 327/365 Vette heads. Appreciate the gearing input, most vehicles I've had, including bikes have typically had too low a 1st gear, lighting the tires or running out of rpm too soon, making short-shifting to 2nd the norm. Feathering the clutch a little adds to the experience. I don't place much emphasis on city driving with the car as I'm in a small town, country roads is where I enjoy it. With 3:55's it could see the taller 1st being a problem, with 3:73's I'm on the edge in your opinion?

Sorry for the jack Ron, hopefully you get some info from the input.

Im in a similar situation 3:73s . Right now I have a 700r4 a 3:06 first gear .
I do trackdays , HSAX stuff . I can usually get to the first turn in first with 330 HP . I will probably never have more than 400 HP at the rear wheels
Do I go with a rs400/500 ? or the rs 600, for the better first gear ?
Once under way I do not expect to need first gear with either trans
I did send Keisler a couple e-mails , no answer yet

[KEISLER]

Hey Folks,

We've been selling the RS400 and 500 in the previous packaging T45RSxxx since 2007, and have hundreds of them in the market. With the new case, and close ratio high torque gearing, along with more than 15 PerfectFit versions came the RS last month. Our run rate on the RS now far exceeds that of the TKO, so we'll start seeing a lot more of these units in the field soon. There are T45RS owners here on Lat-g.

Regarding the gearing, there are a couple of considerations. First, the Overall Ratio in first we like to see in the range of 10.x-11.x so that you will have good acceleration from a launch. When the Overall Ratio gets up to 13.x, you may likely feel the car is overgeared - especially if you have a big block.

To understand the difference in gearing a little better, put it in terms of torque multiplication. Let's say you have an engine putting out 400HP and 400LBFT over the power band. Multiply the torque by the gear ratio, and that is the output torque generated out of the transmission (example: 400 LBFT x 3.37 = 1348 LBFT torque in first gear with the RS400/500; or 400 LBFT x 2.80 = 1120 LBFT with the RS600). That's torque gain is great from the point that you can bring your car into motion quick. The downside is that your wheel rotational speed for any given engine rpm will be slower with the numerically higher gear (ex, 3.37) than with the numerically lower (ex 2.80) first gear. Also, because of the law of physics that energy is neither lost nor gained, the HP at the output of the transmission is inverse multiplication of the HP at the input ... meaning that HP in first gear is 400 HP / 3.37 = 119 HP for the RS400/500, and 400 HP / 2.80 = 143 HP for the RS600. Now, understand that the RS400/500 does not use more power than the RS600 in first gear. But simply it makes more torque, but equally less horsepower.

Gear multiplication occurs once again at the differential, with the main difference being that the diff affects ALL gears. The 3.73 is perhaps the most popular GM performance gear because it offers considerably more torque multiplication across all gears than say 3.36. So the 3.73 happens to be what I have found is on the end of the scale for pairing with the RS400/500 and a big block or hot small block. So, 3.9 and numerically higher we generally pair with the RS600 to prevent over-gearing in first.

Now, you have to put this into context as to your engine's output at a given rpm. For the case of the Duntov cam'd small block, that engine doesn't make a lot of bottom end torque, but likes to rev and make HP on the top end. So, that engine can benefit from the additional torque multiplication to get the car motivating without having to slip the clutch excessively. Combine that with the higher rpm redline to make a really fun blast from first gear. For the case of a low end (rpm) torque monster big block, the numerically high first gear of the RS400/500 coupled with lots of engine torque means there will be a whole lot of torque at low rpms, and the consequence may be excessive wheel spin right from the start.

Looking at real world examples is another good point of reference. All Mustang GT w/5-speed cars since the 90s through 2010 run 3.3 first gear ratios. And there are a lot of fast (10.xx sec 1/4 mile) Mustangs running the 3.3 first gear ratio.

Rolling all of the above into consideration, my general guideline for muscle cars running 25-27inch tires is this:

Engines up to 500 torque and 500 HP:
diff ratio of 3.08-3.73 => use RS400/500
diff ratio of 3.9 & up => use RS600

Engines up to 600 torque and 600 HP:
diff ratio of 3.36-4.1 => use RS600

We always discuss these points with the owner/builder during the quote, and any questions or special considerations (large tires, special purpose apps, etc) can be reviewed.

Hope this helps you all to understand the impact of gear multiplication and selection.

Shafi Keisler

[Sieg]

Thanks Shafi, great delivery of information. Your time is much appreciated.

[Sieg]

How many people have experience converting their car from a mechanical clutch linkage to hydraulic?

How's the pedal feel/feedback?

I can see a few potential benefits:
- Less clutter in the engine compartment
- Ease of installation
- Header clearance
- Use of heavier pressure plates

Any downsides other than price?

[KEISLER]

Hi Sieg,

This is a good question, but I recommend you start it as a fresh thread. And check our customer testimonials section for lots of first hand feedback on this.

Shafi

[gnx7]

I had a GForce GSR dog box in a race car and it has no business being on the street. The sheer whine is for a race environment only. It shifts instantly and is one bad mofo with a zillion gear ratio options. Another plus is that they are around 60lbs..... saving an easy 70lbs from swapping away from a T56.... and then another 20-30lbs with running a lightweight 7.25" triple disc clutch/PP/flywheel setup (mine was 13lbs total).

Once again... this transmission is not a street transmission by any definition. Straight cut gears and dogs for gear engagement are brutal on the senses over time.
The 4 speed dog boxes are affordable. The 5 speeds which are yet again a step up with little compromise in gearing... are super $$$'s.