Close or wide ratio t56? - Page 2 - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #16 of 28 (permalink) Old Aug 10th, 19, 3:18 PM
rkd
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Re: Close or wide ratio t56?

As other have noted, run the numbers for both trans, and try several rear axle ratios.

You may find that a 4.10 or so axle and the .50 od gives you a really good higway gear. My Bullitt, with a 3.73, does lots of highway time, and I think would be even better with a six speed and another od gear.

The opposite though would be that you don't want dump truck low gears, they make for a very short first gear run.

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post #17 of 28 (permalink) Old Aug 10th, 19, 8:40 PM
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Re: Close or wide ratio t56?

FWIW, I believe Tremec has changed the OD gearing on the Magnum. I read the 80/63 combo is now the norm for both close and wide ratio models. I think the 74/50 gears can be installed as a dealer option for those that want them.
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post #18 of 28 (permalink) Old Aug 10th, 19, 11:53 PM
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Re: Close or wide ratio t56?

Quote:
Originally Posted by NorCal-SS View Post
FWIW, I believe Tremec has changed the OD gearing on the Magnum. I read the 80/63 combo is now the norm for both close and wide ratio models. I think the 74/50 gears can be installed as a dealer option for those that want them.
Depends when this happened. I just ordered mine a month ago and it was still an option.
Really, I don't feel the .5 is necessary though.
Even at 70ish I am cruising around 2k... that is already low to begin with.
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post #19 of 28 (permalink) Old Aug 11th, 19, 1:53 AM Thread Starter
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Re: Close or wide ratio t56?

Leaning towards the close ratio.

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post #20 of 28 (permalink) Old Aug 11th, 19, 4:12 PM
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Originally Posted by 67camaro69 View Post
Leaning towards the close ratio. <img src="https://www.chevelles.com/forums/images/smilies/beers.gif" border="0" alt="" title="Beers" class="inlineimg" />
This is not a good decision in my opinion. Wide ratio with a deep over drive will trump a close ratio in almost every situation. Myself being someone whom drives there car more than most, here’s what I have learned why a wide ratio is better.

Big cam in your big block... wide ratio easier to get off the line in all situations
Stop n go traffic, wide ratio
Lightweight flywheel, wide ratio gives you the SLR
Lightweight flywheel and big cam, wide ratio for sure
Live in a area with a lot of hills, wide ratio
In drag racing and under 700hp, wide ratio will yield better 60fts
Deep over drive will always yield better mileage

Most will say your going to have traction problems. Ok logically if you have a traction problem, a ratio change is not going to fix it. Better suspension setup will.

Close ratios are good if you have a engine that does not make much torque or want to keep things in the zone. For Genral driving/cruising you will be shifting more because of the gear spread being close.

Your driving a big block, it makes torque so use it. There is no need to keep rpm spreads to a minimum. As well tie this up with a sniper or fitech and you should yield 20mph at highway speeds cruising at 80 or better.
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post #21 of 28 (permalink) Old Aug 11th, 19, 5:44 PM
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Re: Close or wide ratio t56?

For the street, there is a possibility of it bucking at lower speed, in the higher gears, even with the close ratio. I wouldn't even consider the wide ratio for mostly street driving because 6th may be choppy. Your mild cam might save you, but I wouldn't trust it. At 70mph: 1750 rpm in 6th for the wide ratio vs. 2200 rpm 6th for the close ratio. But, this is only my opinion.

My car has a close ratio T-56 Magnum (502 600hp/594tq, bigish HR cam, EFI, 4.10 gears, and 28" tires), and I'm very happy that I chose the close ratio.
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post #22 of 28 (permalink) Old Aug 12th, 19, 12:55 AM
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Quote:
Originally Posted by GoFast Beaumont View Post
Quote:
Originally Posted by 67camaro69 View Post
Leaning towards the close ratio. <img src="https://www.chevelles.com/forums/images/smilies/beers.gif" border="0" alt="" title="Beers" class="inlineimg" />
This is not a good decision in my opinion. Wide ratio with a deep over drive will trump a close ratio in almost every situation. Myself being someone whom drives there car more than most, here’s what I have learned why a wide ratio is better.

Big cam in your big block... wide ratio easier to get off the line in all situations
Stop n go traffic, wide ratio
Lightweight flywheel, wide ratio gives you the SLR
Lightweight flywheel and big cam, wide ratio for sure
Live in a area with a lot of hills, wide ratio
In drag racing and under 700hp, wide ratio will yield better 60fts
Deep over drive will always yield better mileage

Most will say your going to have traction problems. Ok logically if you have a traction problem, a ratio change is not going to fix it. Better suspension setup will.

Close ratios are good if you have a engine that does not make much torque or want to keep things in the zone. For Genral driving/cruising you will be shifting more because of the gear spread being close.

Your driving a big block, it makes torque so use it. There is no need to keep rpm spreads to a minimum. As well tie this up with a sniper or fitech and you should yield 20mph at highway speeds cruising at 80 or better.
I would generally agree with you but with a cammed engine the deep overdrive would be useless.
The close ratio would allow the engine to stay near peak power longer so it would be better all the way around for street driving-- that big drop when shifting wouldn't cause weird circumstances where you need an in between gear.
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post #23 of 28 (permalink) Old Aug 12th, 19, 1:26 AM
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Re: Close or wide ratio t56?

I went with the close ratio and I am happy with it.

With the 3.31 gears, street driving wasn't a problem. Ceramic RXT clutch was a bit chattery. Sure I would have liked a 2.97 first gear with the 3.31s at the drag strip, but stop light to stop light the 2.66 gear was nice. Once the car is moving, the gear spread is really enjoyable and you can always find the right gear for the speed you're going. If I had a 0.50 6th with my 3.31s, or even 3.55s, it'd be useless below 120 kph. Speed limit here is 100 kph.

Now I have gone with 3.91s, but haven't driven it yet to compare. But now my first gear SLR is 10.40, which is plenty of a street/strip car. 6th gear won't be as nice, the 0.50 would be more ideal now, but I think still fine, especially since I don't highway drive it that often.

If you want spend the big bucks, look at Liberty transmissions. They make a Magnum based gearset with 2.71 first, and 0.54 6th. Pretty much perfect.

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post #24 of 28 (permalink) Old Aug 12th, 19, 8:18 AM
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Re: Close or wide ratio t56?

I always liked 114-116 lobe separation for street cars.. Spreads out the power more but with all the gears you have in that set up it might not be a good idea..
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post #25 of 28 (permalink) Old Sep 15th, 19, 8:09 PM Thread Starter
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Re: Close or wide ratio t56?

Quote:
Originally Posted by GoFast Beaumont View Post
This is not a good decision in my opinion. Wide ratio with a deep over drive will trump a close ratio in almost every situation. Myself being someone whom drives there car more than most, hereís what I have learned why a wide ratio is better.

Big cam in your big block... wide ratio easier to get off the line in all situations
Stop n go traffic, wide ratio
Lightweight flywheel, wide ratio gives you the SLR
Lightweight flywheel and big cam, wide ratio for sure
Live in a area with a lot of hills, wide ratio
In drag racing and under 700hp, wide ratio will yield better 60fts
Deep over drive will always yield better mileage

Most will say your going to have traction problems. Ok logically if you have a traction problem, a ratio change is not going to fix it. Better suspension setup will.

Close ratios are good if you have a engine that does not make much torque or want to keep things in the zone. For Genral driving/cruising you will be shifting more because of the gear spread being close.

Your driving a big block, it makes torque so use it. There is no need to keep rpm spreads to a minimum. As well tie this up with a sniper or fitech and you should yield 20mph at highway speeds cruising at 80 or better.
I have not bought the transmission yet. But i forgot to mention that im not the going to keep the big block for long maybe a year. then im going to start building a LS2 for my car. I think the LS2 and the close ratio magnum would be a good fit together. thoughts?

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post #26 of 28 (permalink) Old Sep 15th, 19, 8:55 PM
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Re: Close or wide ratio t56?

Update from my close ratio T56 and 3.91s. On the street, I can say the 1-2 shift comes much earlier. Before you even get through the intersection. For me, I wouldn't want a 2.97 1st gear on street driving. In fact I prefer the 3.31's just for driving around.

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post #27 of 28 (permalink) Old Sep 15th, 19, 9:35 PM
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Re: Close or wide ratio t56?

with a .5 OD, the 3.73's will effectively be 1.86. That is a A LOT of OD that will likely only ever be used on the highway.

Look at it this way, once you get up to 70 and shift into 6th, your rpms will be at 1755. Make sure your engine will like that.

I think I'd like that with my Chevelle and its smaller cam lol.

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post #28 of 28 (permalink) Old Sep 17th, 19, 1:40 AM
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Re: Close or wide ratio t56?

Quote:
Originally Posted by 67camaro69 View Post
I have not bought the transmission yet. But i forgot to mention that im not the going to keep the big block for long maybe a year. then im going to start building a LS2 for my car. I think the LS2 and the close ratio magnum would be a good fit together. thoughts?
still a wide ratio.


my view point comes from my build, a 502 big block + turbo with a 30lb flywheel and a 2.97 first with 3.73. traction is not a problem, again setup the suspension. This year I did a race week / road trip of 4000miles or better. from pikes peak mtn, to yellow stone national park, to the traffic of Denver, to the drag strips around Colorado with a ton of cruising and general driving. I wouldn't have it any other way but a wide ratio transmission. before my t56 days I had a super t10 with a 2.61 first, so I have experienced both setups.

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