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Discussion Starter #1
I'm wondering if anybody has any helpful tips for programming for 2.56 rear gears. Mostly curious about leaving T/C unlocked at maybe more sporty than factory speeds around town or things to look out for on shift points.

I'm trading the possibly grenade'd 1963 3.73 12 Bolt for a 2.56 8.5" 10 Bolt in my C10. So other than the driveshaft I really will have an entirely B-Body drivetrain in the thing.

-Brian
 

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Please forgive me if it looks like I'm stating the obvious.
4L60e: 1st: 3.059 … 2nd: 1.625 … 3rd: 1.000 … 4th: .6969
3.727: 1st: 11.401 … 2nd: 6.057 … 3rd: 3.727 … 4th: 2.598
2.563: ……….….……… 2nd: 7.839 … 3rd: 4.164 … 4th: 2.563 … ???: (1.786)
See what happened there?
T56's 6th gear with 3.727 axle (1.864) is slightly more gear than 4L60E's 4th gear with 2.563.
Think about that.

Before worrying about the 2.563 TCC strategy, get the 2.563 shift strategy right.
Meaning FORGET about 3Up4 & 4Dn3 until your 1Up2, 2Up3, 3Dn2, & 2Dn1 are perfect.
The low throttle 2Up3 & 3Dn2 need more attention than you might think.

By 'perfectly' I mean you want the 4L60E to:
shift as rarely as possible under normal / light driving loads (under 19-25% TPS, depending on road speed)
downshift quickly enough to protect the 4L60E AND the LT1 once MpG is less than paramount

Do not tune tune it while actually carrying an extra ton.
That said, tuning the shift table like it was carrying an extra ton is wise.
Long steep hills were the best help for tuning my 2.563 wagon that I could ask for.
Did you know wagons can fit 10 young women going to a Justin Timberlake show, plus driver?
11 people * about 180lb, is about 2000lb. Luckily my 2.563 shift table was ready.
That particular shift table had no use for 2.563's 4th gear at all whatsoever.
 

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Your 3rd decimal point is giving me a headache ;)
About 2 rpm error at 2000 .
The t56 6th is actually .5026480501 yuck yuck

Edit, mistyped a 5 instead of 6, thanks scot


As for adjusting, I used to data log, cruise around manually shifting where the happy places seemed to be.
Then go back, look at the logs and use them to set the points.
Then go back and see.
Joel could better answer but not sure of the cooler flow in unlocked 4th
If it is feeling happier unlocked most of the time, probably should be in a lower gear.:)

1.76 overall final smacks of "too much of the good idea " unless you live around Wendover Utah
 

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I hope most people tuning already know about what factors affect shifting. I do not have the experience a lot on the forum do but I used the tuning process to get rid of my pet peeves. I hate gear hunting(up/down shifts) so I spent some time with throttle position, gear change speed, and the speeds I drive in traffic. I looked at the common road speeds(around the posted limits) and used throttle position(%) to hold a gear longer.

For example I did what I could to make sure the PCM would use engine torque instead of gear shifting during low throttle bumper to bumper driving.

When you want sporty the PCM will know what to do by throttle %. Or set up the PCM to use the "Performance Shift tables" and add the switch.

I have no experience with a car with a ratio as low as 2.56 but I would try to keep it out of 4th during city driving. I do vote for locking the TC. With my 3.73 I do most of my city driving in 4th with the TC locked and this would be like you doing the same in 3rd.
 

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4th (1.786) is not utterly useless; nor is it necessary. Enough weight, though, makes it useless.

2.563's 4th with the TCC unLocked is ALWAYS a worse option than 3rd.
ALWAYS. Every time.
 

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I'd be looking for a late 60s early 70s 3.08 truck 12 bolt. Bolt in, no driveshaft change, better gears. So many of them out there. Even a mid-late 70s 12 bolt with the 5 lug pattern. The guys on the 67-72 forum will tell you the gear options for each year. One of them likely has a rear for you within driving distance. Truck guys are way worse parts hoarders than us.
 

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Discussion Starter #7
Thanks for the tips guys. I'll start with factory Roadmaster Shift Tables for my tuning and adjust from there. Sounds like I just need to be prepared to hold it in a lower gear more than I'm used to. The other key sounds like it's important to use lock up in the lower gears like normal to keep from cooking the fluid.

I don't actually use this truck as much of a hauler so no worries about putting a half ton in the bed and hitting the road. For all my tuning I really do wish I lived somewhere with hills. Wichita is awfully flat. Also not many curves to go hit either.

As for using a 12 bolt, C10 parts have picked up a wicked price premium these days and I'd still probably end up rebuilding it down the road. I considered rebuilding what I have but 1963 was a weird year. Only year with 10 spline axles (which nobody makes), and the backing plates are press on instead of bolt on which means none of the aftermarket disk swap kits are actually bolt in. So for what I work out to be a few hundred dollars less in the long run I can switch to the 8.5" 10 bolt.

-Brian
 

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For the benefit of anyone else who reads this thread:
OEM 2.56 shift tables - civilian or 1A2 - are not written to protect the powertrain.
They were written to score 17 City & 26 HiWay MpG on CAFE tests.
Using them as a baseline for your eventual shift table is waste of time and fuel.

Better to shift manually, take lots of notes, and write the shift table with the intent of never ever using the shifter again.
 

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To further clarify, that in the lt1 T56 with its horrible 4-5-6 drops.
I have a more usable .84 5th and .57 6th
Unless you require a very high top speed, any T-56 with 4.56 gears is a joy to drive. Very calm at 65mph in 6th with
Richmond 4.56, Aluminum DS and properly adjusted pinion angle and 275/50-17 (28" tall Nitto 555G2's) but a little
frantic with 275/40-17 (25.6 tall Nitto 555) . With 235/75-15 (29" tall tire) , it's downright sedate.
 

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Basically (as in, oversimplified, click the link and read!), 4 GM variants:

1st2nd3rd4th5th6th
3.36:12.07:11.35:11.00:10.80:10.63:1
2.97:12.07:11.43:11.00:10.84:10.56:1
2.97:12.07:11.43:11.00:10.80:10.63:1
2.66:11.78:11.30:11.00:10.74:10.50:1

 

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Scot,
I have a .57 high gear one piece counter
2006 M10 SSR T56 , MW carbon, 4.56 , 255-50-17
I offset that with an engine that pulls hard to its 7200 shut off and has a table top torque curve.
I alternate between a 4.10 assembly and the 4.56.
Either will mph the car into the " you aint gettin out of jail" with ease.
4.10, for me is more senseable with 3.01 first but I usually use the 4.56.

Marky, the 3.01 first M10 notibly stronger that the low first F body , 1st gen V trans
One piece counter, large output, revised syncronizers , bunch of other things.
The male female "screwdriver slot" 5-6 counter drive makes most T56s a trans for ripping through 4 gears then gingerly cruising 5 and 6.
We had all the raz ma taz G force t56 stuff in a road race t56, for a while,,,,,,,,,,,
 

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have a .57 high
There's that missed key stroke again?....Maybe .56 high, then again I never saw a 3.01 first, though I have seen 3.36 with
the .62 sixth. Remember, here in Switzerland "very high top speed" means something different than in the US. Like 180 mph in the left lane and having to move over for faster cars.
 

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1st gear math
input 29 , cluster 38 , I see that as 1.3103448276

1st gear , cluster 17 , mainshaft 39 2.2941176471

I see that as 3.0060851928

I would round that up to 3.01 1st gear , wouldn't you ?

6th gear math
input 29 , cluster 38 , again 1.3103448276
6th , gear cluster 67 , mainshaft 29 .4328358209

I see that as .5671641791

that is ..567

.567 6th gear ,
Closer to .57 than .56 , isn't it ?

Is my math wrong ??

I understand about the sustained speeds, but that does not mean some cars here haven't been up there albeit legally and durations measured in seconds.
 

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then again I never saw a 3.01 first, though I have seen 3.36 with
the .62 sixth.
You identified your trans as a T-56.
Your specs are for a TR-6060, you confused me by misidentifying your trans, but hey like I wrote, I've not seen a T-56 with those ratios. If you'd called it a TR-6060, I would not have written that. Holden, gone but not forgotten.
 

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I'm sure this seems arcane, but now that we live in world where lots of people insist that men are women, among other atrocities, at least if I point out the difference between a T-56 and a TR-6060, no one can call me trans hater.
 

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You identified your trans as a T-56.
Your specs are for a TR-6060, you confused me by misidentifying your trans, but hey like I wrote, I've not seen a T-56 with those ratios. If you'd called it a TR-6060, I would not have written that. Holden, gone but not forgotten.
I didn't mis identify anything scot

While my Pontiac ( Holden ) has a TR6060 which is 2.97
I AM TALKING ABOUT MY 1995 CAPRICE WAGON
The transmission is a 2006 SSR spec T56
It is unique to that application

Only it and the Z06 T56 had the one piece counter
It has the 32 spline output ( larger than Viper ) because of which also the same reluctor count of 40 compared to the typical 17
It has a unique 1st gears ratio..

Waiting for reply
 

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I'm sure this seems arcane, but now that we live in world where lots of people insist that men are women, among other atrocities, at least if I point out the difference between a T-56 and a TR-6060, no one can call me trans hater.
Yeah, but in this case, we can just call you incorrect.
While I have not built as many T56s and 6060s as you, I have had enough apart I know the difference.
 

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but hey like I wrote, I've not seen a T-56 with those ratios. If you'd called it a TR-6060, I would not have written that.
You called for numerical precision:
our 3rd decimal point is giving me a headache ;)
About 2 rpm error at 2000 .
The t56 6th is actually .5026480501 yuck yuck
You can see where my attempt to provide numerical precision, even with a yuck, came from.
After all this, now I'm transphobic.

Per the manufacturer: Gear ratios for the TR-6060
Model
1st
2nd
3rd
4th
5th
6th
Reverse
2007 Ford Mustang Shelby GT5002.971.781.301.000.800.632.90
2008 Ford Falcon Ute & XR63.362.071.351.000.710.573.28
2008 Ford Falcon XR6 Turbo & XR82.981.781.301.000.710.552.90
2008 - Current Holden HSV E Series[2]3.012.071.431.000.840.573.28
2008–2013 Chevrolet Corvette2.661.781.301.000.740.502.90
2008–2009 Chevrolet Corvette Z512.972.071.431.000.710.573.28
2009 Dodge Challenger2.972.101.461.000.740.503.28
2009 Pontiac G8 GXP[3]2.972.101.461.000.710.563.28
2009–2013 Cadillac CTS-V[4]2.661.781.301.000.800.632.90
2010 Chevrolet Camaro SS[5]3.012.071.431.000.840.573.28
2012–2015 Chevrolet Camaro ZL1[6]2.661.781.301.000.800.632.90
2016-Current Chevrolet Camaro SS[7]2.661.781.301.000.740.502.90
2011 Ford Mustang Shelby GT5002.971.781.301.000.740.503.98
2013 Ford Mustang Shelby GT5002.661.821.301.000.770.503.98
2013–2016 SRT/Dodge Viper[8]2.261.581.191.000.770.632.90
2015–2017 Chevrolet SS[9]3.012.071.431.000.710.573.28
2016–2017 Cadillac ATS-V[10]2.661.781.301.000.790.632.93
2009-2013 Chevrolet Corvette ZR-12.291.611.211.000.810.673.11

Gear ratios for the T-56:

Tag IDApplicationTorque Rating (lb.ft)1st2nd3rd4th5th6thRevInput SplinesOutput Splines
1386-000-0031992 Dodge Viper3302.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
1386-000-0051993–1995 Dodge Viper5502.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
1386-000-0061993 Camaro/Firebird w/2.73 final drive "M28"3503.36:12.07:11.35:11.00:10.80:10.62:13.28:12627
1386-000-0071993 Camaro/Firebird w/3.23 final drive "M29"4002.97:12.07:11.43:11.00:10.80:10.62:13.28:12627
1386-000-0091994–1995 Camaro/Firebird4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-011GM Aftermarket4502.97:12.07:11.43:11.00:10.80:10.62:13.28:12627
1386-000-012Mustang 5.0 Aftermarket4502.97:12.07:11.43:11.00:10.80:10.62:13.28:11031
1386-000-013Holden4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-0141996–2002 Dodge Viper2.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
1386-000-0161996–1997 Camaro/Firebird4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-0171998 Camaro/Firebird4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-0181996–2002 Dodge Viper4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
1386-000-0193902.66:11.78:11.30:11.00:10.74:10.50:12.90:1
1386-000-0201999–2002 Camaro/Firebird4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-021Aston Martin4502.66:11.78:11.30:11.00:10.79:10.63:12.90:12630
1386-000-022Holden Commodore3502.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-023Corvette C53752.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
1386-000-0243752.66:11.78:11.30:11.00:10.74:10.50:12.90:1
1386-000-025Corvette Z06 C53852.97:12.07:11.43:11.00:10.84:10.56:12.90:12627
TNET-10774152.97:11.78:11.30:11.00:10.74:10.50:12.90:1
TNET-1247Dodge Viper4502.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
TUET-12594.6 Mustang Aftermarket w/mech speedo4502.97:12.07:11.43:11.00:10.80:10.62:13.28:11031
TUET-12604.6 Mustang Aftermarket w/elec speedo4502.97:12.07:11.43:11.00:10.80:10.62:13.28:11031
TUET-1452Chevrolet Corvette3702.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
TUET-1453Chevrolet Corvette3702.66:11.78:11.30:11.00:10.74:10.50:12.90:12627
TUET-1576Aston Martin4152.66:11.78:11.30:11.00:10.79:10.63:12.90:12630
TUET-16603502.66:11.78:11.30:11.00:10.74:10.50:12.90:127
TUET-16942003–2004 Mustang Cobra4502.66:11.78:11.30:11.00:10.79:10.63:12.90:11027
TUET-1806Dodge Viper SRT-105502.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
TUET-2022Cadillac CTS-V2.97:12.07:11.43:11.00:10.84:10.56:12.90:1
TUET-2060Mustang Cobra4502.97:12.07:11.43:11.00:10.80:10.62:13.28:11027
TUET-2062Dodge Viper5502.66:11.78:11.30:11.00:10.74:10.50:12.90:12630
TUET-2066Pontiac GTO/Holden Monaro2.97:12.07:11.43:11.00:10.84:10.56:12.90:12627
TUET-5044Cadillac CTS-V2.97:12.07:11.43:11.00:10.84:10.56:12.90:1
TUET-6450T-56 Ford N/A XR63.35:12.07:11.35:11.00:10.80:10.63:12331
TUET-7477T-56 Magnum Chevy Aftermarket2.66:11.78:11.30:11.00:10.80:10.63:12631
TUET-7484T-56 Magnum Ford Aftermarket2.66:11.78:11.30:11.00:10.80:10.63:12631
TUET-8274T-56 Magnum Ford Aftermarket2.97:12.10:11.46:11.00:10.74:10.50:12631
TUET-8277T-56 Magnum Chevy Aftermarket
 
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