T56 Questions

I am considering an aftermarket T56 as an upgrade to my Richmond 5 speed because I want overdrive. Has anyone done this conversion? What are the pro's and con's of a T56 vs. let's say a TKO or a new Richmond 6 Speed?

:beer:

I'm not sure but in a T-56 aren't 5th and 6th overdrives? 4th is 1:1? I have RG non-overdrive 5 speed with a 3.08 rear. If i was going to change it I would use a RG 6 speed. I like the close ratio 5 spd of the RG.

Sky65 said:

I'm not sure but in a T-56 aren't 5th and 6th overdrives? 4th is 1:1? I have RG non-overdrive 5 speed with a 3.08 rear. If i was going to change it I would use a RG 6 speed. I like the close ratio 5 spd of the RG.

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I agree with the close ratio and strength of the Richmond 6 speed, but at $3000.00 plus it makes me wonder about the T56 with it's double overdrive gears. An aftermarket T56 is around $2500.00.

Strength aside - (I think the TKO is stronger) - I believe that with standard gears and average (hot) cam the 6th gear overdrive will be too much.

The LS1 and LS2/3 engines run just fine at 1200-1400 rpm at 55-70 mph on the interstate, you can accelerate from 1300rpm without a problem, my C3 does not run that low (383ci with roller cam dur230-236)

I do not believe you'll ever use the 6th gear unless you risk a speeding ticket at 95mph.....

Other than that it's a great tranny - I love it in my C6

If I am not mistaken, the factory T56 comes with a .74 and a .50 5th and 6th gear, the GM aftermarket T56 is available with a .82 and .72 (or something close to that), which seems to be better suited for a street/muscle car
What rear gear ratio do you have in your 79 and what kind of cruising RPM's do you experience at approx. 70 mph?

:beer:

Hi

Pls see my answer here http://vettemod.com/forum/showthread.php?p=25386#post25386

If you want more info, let me know.

Pics are available , on the German Forum or US Forum or if you want, by E-mail.





Rgds. Günther

Hi

Shifter outlet, so cutout of the tunnel.
It runs then under the console and exits at the right place.



after installingn the original inner boot, all is closed again.





Here with the original M21 shifter stick modified to adapt to the T56.



rgds. Günther

Wesch said:

Hi

Shifter outlet, so cutout of the tunnel.
It runs then under the console and exits at the right place.

after installingn the original inner boot, all is closed again.

Here with the original M21 shifter stick modified to adapt to the T56.


rgds. Günther

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Hey Gunther, Thanks for the pics and the information, they are great! Did you have to modify the parking brake cable/pulley?:fishing:

:beer:

Hi

Yes, I had to shorten the upper cable because I installed the auto crossmember
a couple of inches further back as original , because the T56 is much longer.

I also modified the crossmember tranny seat so that the T56 sits directly on the crossmember and not on a bracket like the M21.







The reason I installed a auto crossmember only slightly modified is because of our governmental car technical check ups done Bi-yearly on Oldtimers. It appears oiginal and they did not say anything. Would I use one of the aftermarket tube frames, they probably complain. Did not want to take a chance.

Rgds. Günther

DeeVeeEight said:

What rear gear ratio do you have in your 79 and what kind of cruising RPM's do you experience at approx. 70 mph?

:beer:

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3.55 gears and roughly 2000 rpm at about 70, I'll have to remember to pay attention next time I drive the car....

I think Wesch mentioned that he has 4.11 gears - I believe that my 1st gear would be pretty much useless with those gears but that's just a guess... the first four gears are perfect as they are now with the 3.55 gears, there is a noticeable step between 4th and 5th gear but it's not all that bad.

I was wondering about that step between 4th and 5th. I am looking more at the TKO 500 as an alternative because of it's .68 overdrive and roughly 3.3 first gear. I think that a TKO 600 is too much overdrive with my 3:23 rear gears.
I still like the idea of the T56.....
So many choices!

:beer:

What's the torque rating on a T56?

1Michel said:

What's the torque rating on a T56?

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Depends on which one you get. The old Ford units were rated around 350/450, some of the aftermarket T56's are rated at 650.

You can get the TKO600 with two overdrive ratios, I think the other one is .82 which will fit your gears better...
I believe that with 3.23 gears you'll be pretty happy with the TKO, the first 4 gears will be a little "longer" than mine - the 5th gear would then be only useable on the highway at 70mph or faster....

FWIW, I am considering switching my diff.to a 2.73 from the present 3.08. I am running a Richmond 5 speed, and cruising at 70 mph is a little high on the rpm's. Will still leave me with a reasonable first gear (8.93), about the same with a m-21 with 4.11 rear gear (9.05).

big_G said:

FWIW, I am considering switching my diff.to a 2.73 from the present 3.08. I am running a Richmond 5 speed, and cruising at 70 mph is a little high on the rpm's. Will still leave me with a reasonable first gear (8.93), about the same with a m-21 with 4.11 rear gear (9.05).

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I considered this option but was told by my mechanic that I need a 2 series carrier for the gears - I have a 3 series - also the (minimal) RPM drop in 5th gear would be seriously offset by the lack of performance in first gear (for my gears). It is more expensive to switch out the trans. but the results are better too.

Hi

For a 1/4 mile race, my 1st gear might be unusable with the T56 and 4.11 rear end, but for corso driving etc it is just perfect.
With the 3.70 rear and close ratio M21, I had to slip the clutch a lot with this slow driving and I am not Superman.
I find the 1st gear being perfect and I can basically walk beside the car at 800 RPM now.
1st gear is good enough to get off and a fast shifting into 2nd keeps the cars nose up high.

You need to know what you use your Vette for to decide gear ratios.

I find the T56 with a 4.11 being exactly what I was looking for.

Rgds. Günther