Trans gear vs. rear gear ratio ?'s

DeeVeeEight

DeeVeeEight

Fast Pedalphile
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Southern New Jersey, USA
What is an optimal first gear ratio? I thought I read somewhere that 10:1 is desireable.
What is a good manual trans. overdrive ratio for a carbed 383 with a 3:23 rear gear ratio?
I just rebuilt the rear about a year ago. Is it worth changing the rear gear ratio back to something like a 3:73 to take advantage of the gear ratios available in many of the Tremec transmissions?

I am mainly looking to improve highway cruising RPM's. I take the car to the drag strip once or twice a year.

:fishing:
 
A C3 corvette had a 2.2 and 3.36 = 7.392
I think the LT1s came with 2.2 and 3.7 = 8.14
 
Modern corvettes have a first gear around 9-10.
(3.42 rear and 2.66 or 2.97 first gear)


to answer your question:
When you have difficulty starting from a stop on a hill.
 
guru said:
Modern corvettes have a first gear around 9-10.
(3.42 rear and 2.66 or 2.97 first gear)


to answer your question:
When you have difficulty starting from a stop on a hill.
Click to expand...

that much is true, but then with that ease of operation there, I always wound up starting out in second gear, and shifting to 4th......

told you all I wuz lazy.....

:harhar::goodnight:
 
DeeVeeEight said:
OK, let me re-phrase that question. Does the total of the 1st gear ratio numbers become unuseable or undesireable in excess of 10?
Click to expand...

I would say so, my wide ratio muncie with that L48 stock engine, and a L98 injection on it...should have had some 350 ft lbs, and 336 rear, with 2.5x first gear...well it was fine even in mountains here on east coast....out west, I dunno, really....

I found the gears just about right for a vette, but really wanted the overdrive...cheepest way was to go automatic.....

and with a automatic, I swear I don't understand the need for so many speeds with a torque converter that's looser.....say ~2000 rpm stall, and lockup, to me it seems a first gear of 2.00 then 1.00, then .50 overdrive for our 3 speed automatic, and get over it already....enough...

All this is so subjective, IMO, it's your opinion that counts, YOU the one driving it....:2nd::thumbs:
 
This is the whole point, the difficult balance between first gear operation, engine operating rpm and top speed.

To low rear end ratio and you will be shifting a lott, to high a rear gear and your car will be a dog.
When I first got my car, it had a high cr 350 with high operating rpm. It also had a 3.08 combined with a M22. The car was a real dog. It would pull to 100 kmh in first, but was very, very slow below 3000, after that you could barely hold on. Roads are not that long here, so I mostly ran out of road with that 3.08 when doing a pull. When driving on the speed limit the engine was constantly turning under its torque curve.
It made it clear to me that I would need a lower rear gear. A 4.11 would be perfect for the M22, but is no fun at the highways.

I looked at the TKO combined with a 4.11, this would keep my engine in its operating range, but first would become mostly unusable, unless pulling to 6000 +. A tko with a 2.20 first would be perfect, but is not available.
 
Well then, let me invite you to look at my options and tell me what you think. I have been struggling with these choices. I like the T56 best.

I have a 3:23 rear gear with a carbureted 383 stroker making about 400 HP.
There are 3 aftermarket transmissions for me to choose from.

1. Richmond 6 speed ($3095.00)
1st gear = 3.27, 6th gear = .76

2. Tremec T56 ($2595.00)
1st gear = 2.97, 5th gear = . 80, 6th gear = .62

3. TKO 500 ($2085.00)
1st gear = 3.27, 5th gear = .68

:beer:
 
Your 383 ci and 3.23 rear would be a great match with a 2.87 first gear TKO 600.

That comes out to a 9.27 first.

The I would go with the .82 OD because the .64 is too much for a 3.23 rear
 
In my many ponderings. I have 2 prefered transmission/rear gear combos

Super T10 with the 2.64 first gear with a 3.36 rearend (preferred 4speed)
Richmond 5speed with the 3.28 first gear with a 2.73 rear gear.

My requirements are as follows: 60 in first gear and 160 at redline in final gear(4th in 5speed)

This is all assuming a 7000rpm motor

I can pick up a Super T10 with the right gear ratios for a couple o hundred bucks. I want the 2.64, 1.75, 1.33, 1 ratios. Nearly the perfect 4speed with the 26.2" tall tires.
 
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guru said:
My requirements are as follows: 60 in first gear and 160 at redline in final gear(4th in 5speed) This is all assuming a 7000rpm motor
Click to expand...


Only 160 mph @7000 would suck for most driving.

Ideal high speed gearing is to have peak HP and top speed be the same. That is why I was able to achieve @175 mph at 6500 rpm with only 355 ci
 
My spedometer only goes to 160mph. Seemed a pretty natural top speed.


If I had the richmond 5 speed I would be reaching top speed at around 185 at 6500rpm and 200mph at 7000rpm.

The super t10 with the 3.36 rearend is essentially the richmond 5 speed with a 2.73 rearend without the last gear.

160 would be 6894 RPM

to reach theoretical topspeed at theoretical peak power I would need a 3.08 rearend or around 6320rpm, a 3.23 rearend would put 160mph at 6600rpm.

Now interestingly enough the Super T10 2.64 rearend with a 3.08 is about the same as the 2.2 in my muncie with a 3.55 (which I have).
 
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DeeVeeEight said:
OK, let me re-phrase that question. Does the total of the 1st gear ratio numbers become un-useable or un-desireable in excess of 10?
Click to expand...

calc links you can use


http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

HERES OTHER INFO LINKS

http://www.xracingsports.com/tirecalc.html

http://www.5speedtransmissions.com/calculators.html

the answer like most things depends on the application, and the guys above fail to mention tire size/dia., as that greatly effects your rpm band.
on my race car I had a muncie M21 manual transmission and a dana 60 with a 4.88:1 rear gear and 31" tall slicks
thats a 2.20 trans x 4.88 rear=10.74 :1

I was actually slightly faster with that 4.88:1 combo than with a 5.13:1 ratio I tried 2.20x 5.13=11.29:1

and a 4.56:1 set slowed the car also
2.20 x 4.56:1=10.03:1

remember its the rpm band , Taking full advantage of the power curve that your engines operating in rather than the tire speed that counts most.
 
gkull said:
Your 383 ci and 3.23 rear would be a great match with a 2.87 first gear TKO 600.

That comes out to a 9.27 first.

The I would go with the .82 OD because the .64 is too much for a 3.23 rear
Click to expand...

This is why I lean towards the T56, 2.97 1st gear and .80 5th gear. 6th gear would be mostly unusable.

I am running stock tires at 27 inches tall.
 
Yes I had a 98 with a ZF-6. So hopelessly over geared with a .50 OD sixth gear. The car could go faster in 5th than 6th. I installed a 4.10 rear

IMO - if you need 6 gears you just don't have enough power. If you have a broad TQ curve you can go faster by shifting less

I work at a road race car shop. Every 4 speed car has the tranny internals set to a 2.20 first gear and next to no fly wheel and multi plate tiny diameter clutches. They are a little hard to get moving or even drive slow. but the closed ratio sure is fun out on the track.

I really like my TKO 600 equipped Vette
 
It looks like I have found a good deal on a new TKOII with a .83 overdrive. From what I have been able to find out, the TKOII is the same housing as the Tremec 3550 and the TKO 500/600 but built to handle 500 HP. Basically it seems to be the road race version of the TKO 600.

:beer:
 
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Just make sure you consider the bellhousing, driveshaft, shifter location, etc etc etc.

Those things add up quick.

I think keisler offers a TKO-600 with a .8x final gear as well, with all the misc bits included.
 
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