technical

I have a 2002 SS with a 3.42 rear.
I noticed that according to the speedo, first gear can reach almost 50mph.
This didn't seem right until I tried to calculate.
I picked up 2.66:1 for first gear from a couple of websites.

tire size = 275/40/R17
sidewall 275 * .40 = 110mm
total diameter ((110 * 2) / 25.4)+17 = 25.6614in
circum 25.6614 * pi = 80.5767in
in Miles 80.5767 / 63360 = 0.0012717miles

First gear 2.66?
5800 / 2.66 = 2180.4511rpm
2180.4511 / 3.42 = 637.5588rpm
637.5588 * 60 = 38253.5285rpHour

Estimated speed
38253.5285rpH * 0.0012717miles = 48.647mph...

I thought the speedo was lying or something. Do you guys see the same in you cars?
I can't imagine what would happen if there was a higher gear out back.

Is there any transmission mods to "spread" the close ratio's out a bit? Because this seems excessive to me.
I'd like to improve acceleration without sacrificing the top end.

jRaskell

iTrader: (1)

The only way you're going to improve the acceleration without sacrificing top end is to get more power out of the motor. Gearing is 100% shifting the power around. There's nothing you can do with gearing that will provide gains in one area without taking away from another area. It's just mechanical leverage of the power being generated by the engine.

I'm not really sure what you're complaining about here though. Are you saying 48mph is too much or too little for 1st gear? Higher gears will decrease the top speed in each gear. A 3.73 or 4.10 gear would drop that top speed down even farther, forcing you to shift sooner. I can already easily spin the tires in 1st gear.

**Edit**

And the rev limiter is actually at 6200RPM (our tach is pretty slow, and can't keep up with the engine revs in 1st and 2nd gear very well). So top speed in first gear is more like 52mph. Check out this site for all the details you need on gearing vs mph...

http://www.f-body.org/gears/

ActionJack

There is link to calculate gear ratios and speed:

http://www.f-body.org/gears/

technical

I'm kinda complaining that first gear is too high. I don't want to swap out the 3.42's in the rear. I want to swap out the 2.66 first gear and 1.78 second gear in the transmission for something lower say 3.00 for first and 2.1-2.25 for second. This would provide the better acceleration in the lower gears and keep the nice cruising gears up top. This wider setup is something I see on foreign cars more often since they usually have smaller motors and lack the low end torque. Muscle cars have always had that close ratio style trans.

The question really is: Is there any place I can find aftermarket gears for the T56. I've been searching the sponsers and other websites, but I can't find any. Thought you all might know some "inside" info.


BTW. Thanks for the link to the speed/gear calc. Beats having to figure it out on my own.

technical

Ok, I was looking in the wrong place. Apparently Cadillac already thought of it. From the CTS-V: Tremec T56 :
1st - 2.98:1
2nd - 2.07:1
3rd - 1.43:1
4th - 1.00:1
5th - 0.86:1
6th - 0.56:1
final 3.73:1.

So anyone know if this trans would cause any headaches going into an F-body? Or anything at all about this trans?

VIP1

Last I heard, thats the same transmisson in the F-body. Maybe they changed first?

No. Typically, muscle cars have had gear boxes with wider spacing of the ratios becuase the power they made was sufficient to deal with it and there were fewer gears available. (3sp and 4sp were the norm) A close ratio gear box has the gears spaced numerically closer together to keep the engine reving higher during acceleration. (There is less of a RPM drop between gears.) Smaller/less-powerful engines need closer ratios because they would stuggle with a wider spacing when the RPMs dropped.

--VIP1

SS98Kid

All i gotta say if you do change the gears get some slicks... even a stock car puts up a pretty good smoke show with little effort and changing that gear will only make it easier for those tires to break loose

Ackattack1

iTrader: (7)

what kinda top end do you want? I think even with 4.10s in 5th gear, the top speed is about 150.

jRaskell

iTrader: (1)

Like I said, I can light the tires up easily in first, and my engine is still mostly stock. Lower gearing isn't going to allow me to accelerate any better in 1st, it's only going to allow me to light 'em up easier. The gear reduction is only going to come into play in the higher gears. And top end, how fast do you really want to go anyways?

And the CTS-V gearing isn't a Cadillac thing. That's the gearing the Z06 uses, and if you compare closely, you'll notice the ONLY gear that matches is the 1.00 fourth gear. All the other gears are difference, as is the rear ratio. If you want gearing similar to the Z06/CTS-V overall, just put 4.10s in the rear. If you want the benefit of the different gears in the tranny alone, put 3.73s in the rear. Swapping that tranny into your car is a lot more effort and isn't going to be any effective difference than just slapping a new rear gear in.

technical

I disagree. Muscle cars tend to have big low-end torque and narrower powerbands than higher revving smaller engines. That narrow flat torque is best served with a close ratio box that keeps the rpm's in that tight powerband. Compare that to something like a '03 BMW M3 that has a 4.23:1 first gear, 2.53:1 second gear and 3.62:1 final. That's how they get that 3000lb car ( with no torque ) moving from a standstill.

I had 4.10's in my old car and hated them. They work on the strip, but suck for road racing. I guess I should have mentioned that I was looking to race road courses with this car instead of just 1/4 tracks. That changes the entire dynamic of how you want to gear a car.

technical

The problem is the two OD's in the M6. You loose too much power with OD. I'd rather have the same overall gearing, but no OD in 5th. Shift all the gears down one and leave the 3.42's. I found the Z06 RPO it's M12. I was only looking for the gears I didn't want to spend a couple grand on a whole new box. I know it can be done, I just can't find the parts.

I love the site. You guys are very helpful. Much thanks!!

VIP1

Muscle cars do have a lot of low end torque, but they also have a broad power band (not a narrow one). Just look their dyno graphs and compare them to newer/smaller engines. You'll notice that the muscle car engines have a broader/flatter power band and the smaller engines are more "peaky".

The gearing in German transmissions is numerically higher becuase the rear gear is numerically lower. American transmissions use numerically lower gearing in the transmission and a numerically higher rear gear ratio. German transmissions also tend to have a 1.0:1 as the final ratio in the transmission while american transmissions have an overdrive ratio as the final gear. Mathematically (final ratio X rear gear) it is almost the same. German transmissions are made this way though, to improve high-end acceleration for the Autobahn.

--VIP1

Ackattack1

iTrader: (7)

why not get something like a richmond 6 speed instead of fusing with the z06 tranny. It has a few options on gearing, 5th gear is 1:1 and 6th is OD.

slt200mph

iTrader: (42)

The Z06 transmission is a transaxle...trans is in the rear..u can't use it in an fbody..unless u want to change the complete drive train and go to IRS

z98

The early LT1's came with 2.97 and 3.36 first gears. The Z06's come with the 2.97 also.

There is probably a vendor that can sell the gears, but you might have to buy more than you actually need.

Actually, those are the same gears available in a Z06. If you want the widest ratios available, get a T56 out of a 93 LT1 6 speed with 2.73 rear end gears:

1 2 3 4 5 6

3.36 2.07 1.35 1 .8 .62 (a 2.97 first gear came with 3.23 rear end gears)

Compared to the transmission in the 94-02 f-bodies:

2.66 1.78 1.30 1.00 0.74 0.50

Z06:

2.97 2.07 1.43 1.00 0.84 0.56

If I had my choice, I'd take the Z06 gearing 1-4 with the .74/.5 overdrives.

I think the Z06 has the low first gear to make up for the low torque of the Z06 cam (everything is relative though )

glen

iTrader: (1)

The time it takes to post here you could have found vendors such as D&D Performance, Forte's and Rockland Standard Gear that can hadle such things.

Also, the time it took to type this was longer than the time it took to find out that the new GTO has 2.97, 2.07, 1.43, 1.00, .85, .54 in a T56 behind a LS1 in the conventional location.

technical

Yeah good point. Hell, I didn't even think of it. That would be perfect. I haven't ever installed one of those before. The T10's were pretty good. Anyone have any opinions about the 6sp? Is it smooth? Easily broken?

technical

Yeah, but the power comes on much earlier with the muscle car. It's a flat torque curve but lower range like say an older Camaro 2500-5500 instead of 3500-8000rpm for the M3. That's why the German trans has that granny gear to get it moving.

I was trying to make note of the larger difference between first and second in the getrag... 4.23 in first and 2.54 in second. I'm almost certain that 6th gear in the M3 is an overdrive while 5th is 1:1.

I think we do agree, but just focus on different aspects of the topic. What you mentioned is what I was looking for. Good acceleration at all speeds.

Gotta get out of those turns!!

VIP1

...and stays longer.
Like I said, look at the power curves.

--VIP1

5w20

iTrader: (21)

3.230
2.105
1.458
1.107
0.848

final = 4.400