High hp/tq application, SINGLE OVERDRIVE, 6spd options?

[DavidBoren]

What are the options for a six speed manual transmission with a 1:1 5th gear? I just cannot get behind the T56 double overdrive. I want a close ratio 6spd, that isn't made of glass, and only has one overdrive gear.

Does it exist?

[DavidBoren]

I was on both (sadly only two) websites, and the Richmond 6 speed is only rated at 450-500ft/lbs of torque, same as their "street" 5 speed. And Tremec has too many overdrive gears. If I had to get a T56mag/TR6060, I would want the 2.97, 2.10, 1.46, 1.0 (1st-4th), and the other set of OD gears (.80 & .63)... making it an expensive choice that still isn't what I want.

What about the Getrag V160/161? Those Supras put some pretty serious power through them. And they have a good spread of gear ratios.

V160 (1-6):
3.83, 2.36, 1.69, 1.31, 1.00, .79

V161 (1-6):
3.72, 2.25, 1.54, 1.21, 1.00, .82

Thoughts on the Getrag? Am I missing some obvious choices?

[T_Raven]

What's your reason for not wanting 2 over drive gears? If every t56 ratio is taller than you want, but you like the spread, just run a deeper rear gear.

[DavidBoren]

I want a 6 speed that actually has one more gear than a 5 speed. And given the price of 6 speed transmissions, I should be able to get what I want.

To me, it just seems lazy to slap another overdrive gear on the end of a 5 speed and then tell everybody that it's a 6 speed. That's my opinion, and it makes it really hard to "settle" for a TR6060.

I don't want to have to band-aid fix my $3000+ transmission investment with low gears out back.

The Getrag V16x is only rated for about 400ft/lbs of torque, and they are both rare and expensive. But at least they have the 1:1 gear in the right spot (5th gear).

Obviously I need to do more research. The hunt continues...

[71RS/SS396]

There are other optional gear sets for the Magnum, but you have to be willing to pay for them. Bowler Performance can build one for you. Iirc the gear ratios are 2.29 1.60 1.21 1-1 0.85 0.76

[T_Raven]

I wouldn't exactly say it's lazy to have a typical 5 speed gear set with an extra over drive, or that it's a band-aid fix to run a deeper rear gear. What you're looking for sounds like a 5 speed with an extra 1st gear. That's kinda the same thing as a 5 speed with an extra OD lol. Tire size, axle gears, and transmission gears all effect RPM in a certain gear and that's really what matters.

For example. If you have 4.10s in a 4th gen F body, which I do and a lot of 4th gen guys do, your final ratio in each gear would look like this:



2.66, 1.78, 1.3, 1.0, .74, .5 (T56)

10.9, 7.2, 5.33, 4.1, 3.03, 2.02 (with 4.10 rear)

So with the V161, if you wanted the same ratio in 6th gear, you'd need a 2.5:1 rear. If you wanted the same ratio in 1st, you'd need a 2.93:1 rear. Those 2 transmissions have really deep 1st gears. Gear sets are weaker when the gear size differences are bigger. That's one reason transmissions with deep 1st gears are rated for less hp/tq.


3.72, 2.25, 1.54, 1.21, 1.0, .82 (V161)

9.38, 5.63, 3.85, 3.03, 2.5, 2.02 (2.5 rear)

10.9, 6.6, 5.4, 3.55, 2.93, 2.4 (2.93 rear)

That trans has a bigger drop from 1st to 2nd and the rest of the gears are closer than a t56. 1st gear in both of the Getrags is way deep. You'd never use it without having super tall gears like what I have laid out.

I guess it all just depends on what gear spread you want, what RPM range you plan to use the car in, and what final ratios you want in 1st or 6th.

[DavidBoren]

Yeah, I'm not a fan of the V16x 1st gear, either. I just like that it has a 1:1 fifth gear.

A custom gear set for a T56, that still has two overdrive gears, is not the answer for my problem. A custom gear set with a 3:1-to-0.6:1 spread, with 5th gear being 1:1... now that would be awesome.

I want something more like this:

3:1 (1st), 2.5:1 (2nd), 2:1 (3rd), 1.5:1 (4th), 1:1 (5th), 0.5:1 (6th)

Why doesn't that exist?

[cwylie]

The V160 might be rated at 450hp but I have seen them take a serious beating behind 1000hp motors.

[DavidBoren]

The V16x is generally found behind high spinning motors, and I am wondering if there would be a difference in its capacity to handle the same torque as delivered by a V8.

Is 400ft/lbs of torque @ 4,000rpms easier on a transmission than, say 400ft/lbs @ 2,500rpms?

[Flash68]

I want something more like this:

3:1 (1st), 2.5:1 (2nd), 2:1 (3rd), 1.5:1 (4th), 1:1 (5th), 0.5:1 (6th)

Why doesn't that exist?

I bet G-Force would build that for you.

[no go nova]

Build a short stroke ls motor with a low lash solid roller cam that will spin to 8500 rpm then that supra trans would work great. theres a few of those trans in 7 sec qtr. supra and the trans are stock!

[DavidBoren]

Build a short stroke ls motor with a low lash solid roller cam that will spin to 8500 rpm then that supra trans would work great. theres a few of those trans in 7 sec qtr. supra and the trans are stock!

I like the way you think...

Hmm, putting a 4.8 crank (3.3" stroke) in an LS7 (4.125" bore) gives you 353ci of high revving goodness. And they spin the LS7 past 7k with a 4" stroke! So imagine what it can do with that little 3.3" crank.

[SuperB70]

I'm also done a loy of homework on this. But havent find a trans that I would like to try out.

Sometime ago we builded a twin turbo gen2 Viper and its been eating transmission like bread. Nothing can live behind that 1475ftlb with just 14psi motor. It has broken all kind of manualtransmissions. The last one was some special ordered G-force, if I'm not mistaken. It brakes fifth and or six gears. Not smallers goes it does not get tractions with them.

I'm building for myself even more powerful twinscrew Viper engine and have desided that there is no modern manual for me so I went alittle differen road.

I have got myself an Mercedes 5speed automatic. From 6L V12 twin turbo, used only in 65AMG and Maybach limusines. In stock, it can handel 1200Nm~885ft lb and can be modified to handel 2000Nm~1475ftlb. Fifth gear is 0.83

In Europe this trans has been used in rallycross- and driftcars with success. And it si so thiny, alot smaller that PowerGlide.

Another Euro manual that many uses is from V12 BMW like 850.