Question 6 speed or 5?

[snkbte]

Opinions please,

Assume I venture to the Dark Side with an LS1 5.7 litre.

The decision that remains is 5 or 6 speed manual. Considering the power to weight ratio would the sixth gear be of any value? I suppose the real question is; is there any benefit to using the 6 speed rather than the 5?

Cheers

SNKBTE

[Cobra.au]

Hi snkbte,
If you are considering to go the ls1 route here is something for you to think about.

There are + & - for both ways.

6 spd: easy to install, very strong, easy to get parts etc but do you realy need 0.5 to 1 6th gear?

5 spd: would only go with tremec 3550 or TKO have to make custom bellhousing not easy gearbox to locate and spare parts can be pricey(in OZ)

Craig W

[Rebel1]

Tough one to answer snkbte because there are so many variables.

Firstly, rear end ratio and tyre sizes have a huge bearing on the decision. As does the purpose of use....street racing, drags, highway cruising.

Factor in all these and do some sums. Here's a link that might help with the sums. http://www.368s.com/tools_rpm.phtml

A trap many on here have fallen into has been to not do the sums properly. Many cobra owners are using 5 speed transmissions but because of their diff ratios find they have a totally useless first or a non-usuable 5th gear.

If one is using a 5 speed...then why not use all the 5 gears available. Why have a 5th gear that drops revs so low the motor is "off the cam" at a highway cruising speed.

Tremec have released a new line of transmissions, the 500 and 600. Increased power rating but more important..better gearing.

[Junket]

SNKDTE I have a Richmond 6sp and wish I had a 5 er with the power to weight ratio you are not in each gear long enough but you get a lot of good feed back from on lookers.
Ken

[justbetter]

I can only speek for myself having the T56 6 speed.

The 6 gear is great, although at 260k it was just about time to change from 5th - 6th so i never got a chance to see how it cruised.

Where it has its very big advantages as i see it.

6th, 110k, 1400rpm, Melbourne to Mt Gambier 420km 1 Tank 65lt.

Its all about fuel economy.

Not to mention i can actually start to hear the radio as it cruises nice with not much noise for a change, helps also when passing those guys with the blue lights on the top, nice and quiet...

[Aussie Mike]

It's all a question of ratios.

I'm running a T56 6 speed in mine and I think the ratio set in the first 3 gears is better than the TKO or TR3550.

1st gear in the the 5 speeds is way too low and there is a sizeable gap between 1st 2nd and 3rd. The T56 has a tall 1st gear @2.66 and a taller 2nd and 3rd gear as well. The actual spread from 1st to 5th is much the same as 1st to 4th in the 5 speed. With the right final drive ratio you have a close ratio 5 speed with an excellent OD 6th for economy.

Here is a comparison of the ratios for the TR3550 and T56

TR3550---------T56
1st--3.27-------2.66
2nd--1.98------1.78
3rd--1.34-------1.3
4th--1.00-------1.00
5th--0.68-------0.74
-------------------0.50

I'm running 3.9 gears in the rear of my classic and I think this combo should work well.
here are the speeds thru the gears for my setup:
1st @ 6K RPM is 71 KM/H
2nd @ 6K RPM is 106 KM/H
3rd @ 6K RPM is 146 KM/H
4th @ 6K RPM is 189 KM/H
5th @ 6K RPM is 256 KM/H
6th @ 6K RPM is Just silly.

However 6th @ 110 KM/H is a comfortable mile eating but not gas guzzling 1745 RPM. And still close enough to the power that it'll pull away easily for passing on the freeway.

Check out all the ratios at TTCs web page: Transmission Technologies

I'll try to stick some TR3550 ratos into a spread sheet as well.

Cheers

[Cameron Parsons]

Good advice, and a great link to that ratio/speed calculator.

I have decided on a TKO500 for the car, calc says good useable rev range.

I won't have the stump pulling grunt of the Darth side, so 6th might be too much.

Garrett, 65 ltrs for 420 K's... nice work, I bet that required restraint

Cameron

[Rebel1]

This is the way I'm going this time around... I think

Tremec 600 diff 3.31 .. following charts are MPH and although it is a 5 speed box and the charts show 6 speeds...there are two model 600's available....diff being the 5th gear... .64 or .82

5th in the charts is the .82 numbers...6th is the .64

second lot of numbers are same except for 3.55 jag diff.

Dont ask me to convert to Kilometers cuz I'm an ole fart so I understand MPH ... besides... i'm too lazy to multiply by 1.61 for ya.

1st: 2.87 2nd: 1.89 3rd: 1.28 4th: 1.00 5th: .82 6th: .64

Tire Diameter 1: 26.6 inches
Rear Gear Ratio 1: 3.31:1
MPH
RPM 1st 2nd 3rd 4th 5th 6th
1000 8 13 19 24 29 37
1500 12 19 28 36 44 56
2000 17 25 37 48 58 75
2500 21 32 47 60 73 93
3000 25 38 56 72 87 112
3500 29 44 65 84 102 131
4000 33 51 75 96 117 149
4500 37 57 84 108 131 168
5000 42 63 93 120 146 187
5500 46 70 103 131 160 205
6000 50 76 112 143 175 224

Next chart follows:

[Aussie Mike]

The 600 has a much better 1st gear than the 3550 and TKO. What's the torque rating on the 600?

Cheers

[Rebel1]

OOpsy...format got screwed:

These numbers ..same box....3.55 diff this time:

1st: 2.87 2nd: 1.89 3rd: 1.28 4th: 1.00 5th: .82 6th: .64

Tire Diameter 1: 26.6 inches
Rear Gear Ratio 1: 3.55:1
MPH
RPM 1st 2nd 3rd 4th 5th 6th
1000 8 12 17 22 27 35
1500 12 18 26 33 41 52
2000 16 24 35 45 54 70
2500 19 29 44 56 68 87
3000 23 35 52 67 82 104
3500 27 41 61 78 95 122
4000 31 47 70 89 109 139
4500 35 53 78 100 122 157
5000 39 59 87 111 136 174
5500 43 65 96 123 150 192
6000 47 71 104 134 163 209

Here's a better set of calculators:

http://www.smokemup.com/auto_math/

Ya gotta register first time but there is no cost

Cheers

[Aussie Mike]

search is your friend. I just found the spiel on the 500 and 600, cool. 500ft/lb for the 500 and 600ft/lb for the 600 that's some impressive numbers.

The T56 is generally 450ft/lb with some models taking 550ft/lb. The standard 3550 is 350-375 and the TKO 2 rates 475ft/lb.

Cheers

[Rebel1]

Yep mike....they look much better than the transmissions they replace.

Word came out about the time I was chatting to you about the T56...thought I'd wait and see.

Much better first.....and choice of 5th gear OD's

[Rebel1]

Wots the bet Mike will spend all night with those Smokemup calculators?

[Aussie Mike]

I've got an Excell spread sheet I made up ages back to calculate all the speeds and RPM based on tyre sizes ratios etc. You just punch in the figures and out pop the results.

What sort of $$$ are the new TKO 500 and 600 boxes going for?

Cheers

[Rebel1]

Yeah....that be right Mike....tryin to re-invent the wheel hey?

Here's a page from Fortes ( advertiser on here) with the prices ($US).

http://www.fortesparts.com/tremec.cfm

Dunno what they gonna be in Oz. but they sure gettin excellent reviews