I am rebuilding a 69 C3 big block (with missing trans). I've got a hankering to install a six speed tranny instead of the 4 speed - I LIKE to have good rip off the line PLUS decent mileage and low cruise rpm...

I've been researching the project, and have found there are some issues/challenges, including Transmission support replacement, and clutch setup conversion - I'll probably convert to the hydraulic setup

The questions I haven't been able to find answers for are:
1. Will a LT1 transmission (ie 94 camaro) actually bolt up to the Big Block engine? (is the input shaft the right length, etc)
2. Which flyweel will I need? - Can I use a "regular" big block 4 speed flywheel?

Thanks!

 

Richmond makes a nice 6 speed (the old Doug Nash). Combine it with the right rear end you can get what you are looking for. Mods are really minor (some work on the tunnel and a new transmission mount). There is a recent thread in the C-2 forum. Buried deep in Richmond's web site you will find the install intsructions for C-2/3 Corvettes. A friend of mine has one in his 406 cid small block '64 and loves it.

 

Have you thought of the 6 speed tremec......easy to install and the performance is outstanding..Keisler website has lots of info....

 

T56=Tremec

 

Does anyone know which trans they used behind the LT1 in Camaro's? Most likely it'll work with few problems, but I've got no clue which trans that is.

 

The LT-1 transmission is not a direct bolt-in due to bellhousing differences, pull vs push clutch, etc.

Get with the folks at D&D Performance. The have a retrofit T56 based on the Viper unit that will bolt directly to the stock GM bellhousing. You get to reuse your stock clutch. Be advised that this in not a direct boltin and will require mods to the crossmember and tunnel.
http://www.ddperformance.com/GM%20T56.htm

 

T56

Summit has the conversion bellhousings and flywheels.

 

True, but the shifter is too far to the rear on the F-Body T56. On the F-Body, the shifter is either 28.3" or 29.4" from the engine mounting surface. Stock for most Muncies is 23.75".

The Viper/aftermarket GM unit is a much better choice and tougher than the F-Body.

Also the gearing is beter on the aftermarket with a .62 6th gear vice .50 for the F-Body box.

More info here:
http://www.5speedtransmissions.com/6_speed.html

Edit: Add more info
Here is an article on a T56 swap into a C3 back when Keisler offered this transmission:
http://www.vetteweb.com/tech/0407vet...speed_install/

 

I had planned on doing a T56 conversion, but a local shop talked me into going the Tremec TKO-600 route instead (5 Speed).

Thing is, this shop sells T56 but does NOT sell TKOs. So these guy's opinion carried a bit of weight.

Reasons not to go with a T56:

- It's huge (tunnel will be tight, expect to mod it)
- More limited in the HP it will handle (less you get
a Viper unit and change the input shaft)
- Bellhousing issues
- NO Speedometer output (electronic only)

Reasons to go with a TKO-600
- It's not a lot bigger than a 4-speed
- Fits on a standard bellhousing
- Cable AND electronic speedo support
- 5th is about the same ration as 6th on a T56
- Costs a BUNCH less

If you are going to be running it on a high speed track (road) and street the 6 speed might serve you better as you may be able to use 5th on track and 6th on highway.

If you just want the overdrive for highway then the 5speed should be just as good.

I did the 5 speed conversion (without a 'kit'). Had to mill the torque arm support off (suppliers will do this for you) and had to make a bracket to support the trans mount from the existing cross member. The trans sho provided the offset shifter. Everything else was off the shelf common stuff that just bolts up. I went with OEM clutch linkage (my frame had the z-bar bracket).

Doing either conversion with the engine in the car is a bear. With the 6 speed option, you may want to seriously consider making the cross member removable.

I bought mine from:
http://www.standardtransmission.com/

Joe is the man, he used to own a corvette shop so he knows what you need: joed@standardtransmission.com

They have a simple replacement shifter arm that moves the shifter over and back to get it in the right place. I think you may need to raise the back of you console a 1/2" or so to clear this one. They will install their shifter for you. The other option is the mcleod side shifter that is hundreds.

 

We have a tremec 5speed in our '68. Fit right in with no modification. However, i've installed a richmond 6speed in a 1971 jaguar xke and that required heavy modification to the tunnel. I'm not sure if the 6 would fit very easily or not. They are both wonderful transmissions but I can tell you you won't be dissapointed with the tremec 5speed if you go with that instead of a 6.

 

The T-56 is available with a standard mechanical speedo output. It is also available to mount to a standard Muncie style bellhousing and use all the standard clutch linkages.

 

We have the adapter plate to use with the t56 if you want to mount it to the stock muncie bellhousing. Also you could just go with a hyd clutch and then use the clutch housings like many of the newer camaros do. The Viper trans only comes in electronic output but there are numerous shops out there that do the tailhousing modifications to run mechanical.

 

I'm not sure I'd call that "better" gearing - you're going to get more top end speed from the .50.

 

Here is my T-56 (actual Viper...not based on) installed. I love it. 1700 rpm @Mph.

The ratio is such that I sometimes skip first but I love rowwing the gears and downshifting...having options...the MPG.

I am still trying to calculate MPG but I either race or forget the reciept. What I do know is that I have about 200 miles on the current tank and about a 1/4 tank left.

For anyone thinking of doing this...This is the single most favorite thing I have ever done to my vette. DO IT. Hit me with a PM for gotchas there are a few and they may cost you money.