6-speed?

[Jughard]

I wanted to find a 6-speed transmission for the 427 S/C.I hope someone has a connection to find it.Let me know please .Thank you

[Jughard]

I also need some tips on why or why not put a 6-speed in.thanks for your time.

[Hal Copple]

Several Superformance cars have Tremec T 56 six speeds in them, i have driven one. I wanted more gears to stir in my car, so i asked Bob Olthoff, my east coast Superformance dealer, about installing one. It can be done in an SPF because the differential is a fixed IRS, not a solid axle, as the driveshaft is only about three inches long. Six speed gearboxes are pretty long.

He patiently explained to me that in a high torque engine like mine, a Stroked Windsor, the extra gearing was not just a waste, but would actually be slower in my quarter mile drag times. He told me that in a small displacement, peaky power engine, something like a 289 motor, a six speed would be useful to keep the engine in the narrow power band, but in a car with a broad power band, i would be wasting time shifting. He told me that the six speed drivers tended to skip gears most of the time anyway, due to the close ratio gearing.

Unless you road race for money, it isn't worth the money. Better to spend that sum, probably about $3000 or more, for another upgrade. No wonder the small revvvy Japanese motors need the six speeds, but not cars like mine.

I am not getting a six speed, but staying with my five speed Tremec.

[Ken Greene]

hmmmm sounds like a vette

:P

[Back in Black]

Because my 514 does NOT have a wide powerband, and I wanted a low off the line 1st gear, AND real top speed abilities, plus low freeway cruising rpms. The ROD has the G-force shift linkage, which is excellent. I like the 6 speed because there is a gear for every occasion, without lugging or overrevving my motor (although it is getting the rev limiter too)
My West Coast cobra has plenty of room for this longer tranny, because the car is 6 inches longer overall than an original (4 inches wider too)
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Here's the Richmond Gear website: http://www.richmondgear.com/cat/trans.html
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[Bob Putnam]

The T56's gear spread is very wide. Sixth is mostly there to give good gas mileage. The Richmond Gear 6 speed is much better, but expen$ive and long, making it a poor choice for a solid axle car. For the street, a 5 speed TKO or Richmond Gear should give you everything you need if you have a powerband that's not motorcycle-like.

[blykins]

Guys, if you actually look at the difference between a T-45 and a T-56, the gears are actually pretty close to each other. The only difference is with the 6-speed, you get two overdrive gears, which really wouldn't help you any in racing anyway. What it would be good for is crusing on the highway with a really low rearend gear.

Here's the difference:

T-45 T-56

1 -- 3.37 3.36
2 -- 1.99 2.07
3 -- 1.33 1.35
4 -- 1.00 1.00
5 -- .67 .80
6 -- N/A .62

So it's not like swapping trannies is gonna give you a more narrow gear range or wider gear range. The only difference is the range in overdrives. So with the T-45 you could probably run a 4.11 and that would be equivilent to running a 4.30 with a 6-speed and a higher overdrive gear.

I got these ratios straight from Tremec's page.

If I were running a big low rearend gear, I'd want the extra cog for gas mileage purposes...but if you're anywhere in the 3.27-3.73 range, you should be fine without it.

In the Vettes and Vipers (Z28's and Trans Ams too), the 6th gear is usually even higher than that... a .50 ratio. I've driven all of these cars, and when you shift them into high gear at around 65-70, they run at around 1100-1200 rpm.

But I guess my main point that I'm stammering around is that the 5th and 6th gears are overdrives anyway, and wouldn't help you any...in a road race or any other situation except cruising.

[Double Venom]

We run the T-56, 6-spd. in all our DV cars. Yaah they're ok, tried them with 3.08's all the way to 4.11's.

Still very seldom used 6th. Rarely 5th on any course that we have been on.

Nice option, but in my opinion not a necessity.

We run these in CR's cars, 4" longer wheel base with straight axles, (and indpendants) and never a problem. Our Drive shaft, if I remember correctly, is right around 18's.

DV

300 Cobras is NOT enough!

[Jughard]

i really appreciate your answers,but forgot to specify the reason why i possibly wanted a six-speed.I just wanted to be able to cruise on the freeway with low RPMs,which would help gas mileage(not too important), noise and engine wear.You explained it well blykins and i just wanted the reassurance and opinions.thank you guys for your help.

[ls1ac]

I am using the t56 but the R or aftermarket gear ratio.
It is wider at the bottom and closer at the top.
I understand that there is a significant loss of power in 6th, but the only time I use it is on the highway at 70. It is quiet (relitive term) and efficicient.
I am using a small 346 cu in engine with high rev 7000.
It works very well.
On the track I seldom get out of 4th.
Seems to be the best of both worlds in one for me.

[Cobranut]

I really don't see the need for a 6-speed either, unless you plan on running a small displacement engine.

We also have a Superduty diesel with the 6- speed, and I skip gears in it all the time when not towing. 2'nd-4'th-6'th.

DV,

CR must have the engine set further forward in the chassis to have an 18" driveshaft.

My driveshaft is just under 9" with a TKO. My water pump pulley is several inches behind the front wheels. Maybe that's how I managed a nearly 55% rear weight bias.

Later,

[Double Venom]

Cobra nut,

The CR's is 4" longer WB., which helps. The DV's come in right at 50/50 with a 190 lbs driver. The DV II is set up 49/51. When we build 'em, we kind of go by the owners wishes.

If I remember correctly, (been a long, long time) my DV turns 1900 rpm around 70 mph in 6th gear?? Damn, I honestly can't remember! That's with the 3.55 gears.

DV

300 Cobras is NOT enough, and neither is 4 Hotels!

[Bob Olthoff]

Hal
Your driveshaft is actually 9.5 inches long.
Bob.

[Jack21]

Am using the 2.95:1 1st T5Z. Got it from Liberty Racing Transmissions who blueprinted it, and swapped out the OD gear for a .80. Rear is 3.55:1. The OD is there for highway cruising. Had I used a taller rear gear, 3.73 or 4.10, I'd have left the OD stock. Wanted the cruise RPM just over 2000 for the cam I'm using which works better at that RPM. In this case, 60MPH = 2000RPM in OD/5th.