myc3

I would like to install a T56 but I am being told by one transmission vendor that I will have to modify my tunnel to make it fit. When I contacted another vendor I was told I would not have to modify the tunnel. I know I will need to modify the crossmember and the driveshaft. I do not want to cut the tunnel if at all possible.

Can someone who has done this install tell me what is true?

Gordonm

Just finishing up my T56 in my 72. No tunnel mods other than where the shifter pokes through are needed. You will have to put in a different hole for the shifter. The T56 is much longer and the shifter comes up in the center and further back. This is no easy install either. There are lots of problems. Nothing that cannot be solved but if you want any more info let me know. Mine came out of a 06 GTO. Some of the aftermarket ones the shifter is in a more favorable location but it is still centered.

63mako

D&D Shifter is offset to fit. It bolts right to the existing bellhousing and uses a stock clutch and clutch linkage. Also has a mechanical speedometer. Crossmember and driveshaft are the only mods required.

Gordonm

Yes for 3600 you can have one. You also need a different pilot bushing As I recall. That shifter comes up in the same location but I'll guarantee you will need to do some fiberglass mods where the actual shifter comes up. That part of the trans is right up to the fiberglass so the shifter bulge will need to be clearanced.

63mako

yes, they are not cheap. Need roller pilot bushing. Good option for those of us without Gordon's fabrication skills and really nice shop.

myc3

Thanks for the info. That is what I was told by D&D today but I just wanted to get this confirmed before I made the buy. My concerns were tunnel fit and shifter location.

Based on your experience is there anything else for me to watch for? This will be going in a 77 that was an automatic. It will be behind a SB 427 and in front of a 3.73 diff. I want the .80 5th & .62 6th Ratios.

myc3

Based on what I have heard from D&D Performance and knowledgeable Forum members I am assuming that installation of the D&D T56 will not require tunnel modifications and the shifter location will be good.

Now a new question.

Does anyone know if the shifter console in a 77 will need to be cut to allow the movement required for the 6 speed shift pattern?

Gordonm

I still say you are going to have to do some cutting. Here is a T56 in a C3 install that might be of some help.

http://temp.corvetteforum.net/c3/gwhite75/index.htm

myc3

Thank you for the informative article. It looks like the only significant cutting is to make the hole for the shifter. I expected that since my 77 is an automatic car.

I appreciate the help.

72LS1Vette

I have a factory Hurst shifter on my T56 and the throw is ~1" front-to-back (1st-2nd) and 1/2" side-to-side (1st-reverse). That should easily fit within the 4-speed shifter opening. I'll know for sure this weekend since I finally had my offset shifter welded up and I'll be installing it to make sure my measurements were correct.



Rick B.

myc3

Please post an update or send me a PM when you finish the install. I am very interested in knowing about any problems or issues you encounter trying to make this fit.

Thanks

WESCH

Hi

This ia D&D Viper T56 beside a M21.
The shifter location is nearly OK, but not exact.
It needs to be put about 1 inch further to the right and back.
I made up a adapter piece and used the original Vette shifter lever for this.

Here you see thast the position is not OK.

Here a temporary shifter for trying. This position is correct . You can see on the left side the bolt where the D&D shifter was boltet to.

Here you see the tunnel cutout that is required. To the left a bit forward is the original cutout for the M21.

Here the Vette shifter on the home made adpater plate boltet to the D&D shift lever.


all this on my 68 BB

I had to change the rear from 3.70 to 4.11 in order to be able to use the 6th gear.

Rgds. Günther

myc3

Thank you for great pictures, that is exactly what I wanted to know. I have two questions:

1. If you did not make the adapter and center the shifter would it still work?

2. I have a 3.73 diff. Wouldn't a 4.11 diff make 1st gear very short? I thought with the 3.73 I would only shift to 6th when on the highway cruising at 75 mph. The rpm's should be 2160 at that speed. Is that a problem? That is about the same rpm's as a TKO600 with the .64 5th gear.

WESCH

Hi

The Viper T56 has a 6th gear 0.5:1.
I suspect that today's T56 have 0.65:1 or so, so 3.70 rear should be fine.
My BB works best at slightly over 2000 RPM due to the ignition advance.
It runs below that, but not optimal.
I never tried the shifter in the original D&D position, but suspect that it would not work.
Now having it centered, it makes it just past the center console cutouts in 1st and reverse gear.
A other problem other members had is the tranny yoke. You must use a 1310 yoke because the 1350 is too wide and will not pass the tunnel.
If you have a 1350 drive shaft, you need to use a 1310/1350 adapter universal joint. My 68 has a 1310 drive shaft, so no problem.

Rgds. Günther

enkeivette

You might not have a glass tunnel like these guys. Mine in my 78 is metal. I had to clearance with a mallet around the middle of the trans a bit. Just in front of the shifter.

1st gear is long in the T56. OD is .5, it works fine even with my 3.55.

63mako

My T56 has a .80 fifth and a .62 sixth.

Gordonm

The GTO T56 I just put in has a .84 5th and a .57 6th.

myc3

D&D Performance offers a T56 with optional .80 5th & .62 6th ratios. Those numbers look to be just right for a 3.73 diff. I am thinking it gives me the ratios of the TKO600 RR transmission for the county roads and the deeper OD for the highway. Best of both with a stronger trans.

My 77 has a metal tunnel so if it is necessary I should be able to open the tunnel slightly with a hydraulic ram to accommodate the yoke.

So far I am not hearing anything that is unusual for an auto to manual conversion.

Others please chime in if there are other issues that have not been discussed on this thread.

Thanks to everyone for all the shared experience and advice.

Gordonm

Another item seldom discussed is the reverse lockout solenoid. This prevent you from shifting into reverse when going into 5th gear. When in normal mode there is a plunger that does not allow you to shift into reverse. It is spring loaded with a heavy spring so if the solenoid fails you can put it in reverse but you had better have had your wheaties that morning. Most of the newer cars have this computer controlled so anytime you are under 5 mph the solenoid is activated or there are some other parameters but it is controlled by the computer. So this leaves our non computer cars out on a limb. It is just a simple 12 volt supply. I wired mine to the output side of the brake switch so it is activated when I push in the brake pedal. Some wire it to a switch on the console or some other way. I actually took this idea from the LS1 forum as many guys are using it this way. Some just leave it alone and have a big right arm and force the spring over when going into reverse. I had to severly modify my solenoid as the clearance was not there but it fits in the tunnel now.

Wiring the backup lights is no big deal either as there is a plug on the side of the transmission. Just hook up your existing backup wiring to it. Mine had the CAGS solenoid also. I elected to remove it and put in a plug. I think the one from D&D already has it removed.

myc3

Thank you for this information. These are exactly the types of details I was hoping to capture. All of this will make my install much smoother.

Keep em coming.