OldCarBum

As part of the resto/mod for my 73 I am rebuilding and stroking my BB to 496 cu in with an estimated 600 hp. I'm still on the fence about which transmission I'm going to install.
1. Keep the TH400 and install 3.08 rear end gears for highway cruising;
2. 700R4 or 2004R with 3.36 rear end gears;
3. TKO600 5 speed with 3.36 rear end gears.
Keeping the TH400 and 3.08 rear end gears will keep me at 2384 rpm @ 65 mph but I will loose an overdrive.

What I don't like about the 700R4 and 2004R is the gearing difference between third (1.0) and forth gear (.70). Going from third to forth gear would cause a drop in RPM from 2600 to 1800 @ 65 mph. A 800 rpm loss at speed seems like a huge performance drop and takes me out of my cam specs (2000 rpm - 5800 rpm) with a recommended torque converter lock up at 2500 rpm.

The close ratio TKO-600 with 1.0 forth and .82 fifth gears and 3.36 rear end gears would cause an rpm drop from 2600 to 2133 rpm @ 65 mph with only a 470 drop in rpm between forth and fifth.

The one and only issue I'm having with the TKO-600 is converting over to a manual transmission. I know how to shift and drive a manual, however I'm struggling with the fact that I may get tired of pushing in that clutch to shift at my age, and how long I would keep the car once it is completed over installing an automatic.

My real questions are:
1. Has anyone set up a hydraulic clutch set up on a C3 with the factory power brake booster?
2. For you old guys out there with manual transmissions and increased HP, do you wish you had an automatic over a manual?

gkull

I don't like H-clutches because I think that you loose the feel. I have a 5 speed in my ford 4X4 with a h-clutch. My vette has a tko 600 .64 of and the new modern high hp clutches have very little pedal pressure.

First gear is very important. tko 600 2.87 and 3.73 or even 3.90 is a great combo. I drove around for 20 years with a 4.11 and OD and I thought that it had the best of both worlds. easy to take off and .64 and 4.11 was a good road gear

silver74vette

Well I have been around for a while and I prefer driving manual corvettes. My current car is a C7 Z06 (hydraulic clutch) that is a joy to drive even in traffic. With the torque you will be making at idle it would be a very easy car to drive easy.

My Street rod has a 700R4 and a 3.08 rear end, I cruise right at 2000 at 70 mph. Big block torque is a tall order for a 700R4, but you can get them built to take it.

If you are going to convert, a manual clutch will give you better feel but hydraulic will take the chore out of it.

Edit - Just saw you are in Napa Ca. if you ever go south, go with the auto..... - End Edit

Either way, sounds like you will have one sweet ride!

bfit

I have a tremec magnum with .64 6th gear in my 70 model , original machanical clutch system . 3.73 12 bolt
This works very well.

Neil B

I really like my T56 big block combo. I just re-did the clutch hydraulics using the bracket and Wilwood master from Silver Sport. The bracket was spot-on. It's tight around the booster but it's about as easy as it gets considering you gotta stand on your head to do it.

resdoggie

I'll stick with a manual and non-hydraulic clutch. I have the M21 mated to a Centreforce DFX clutch. As George said, the pedal pressure isn't that bad.

NeverTooOld

A beefed TH700R4 and a set of 3.73's is a terrific combination because you'd get great acceleration as well as a low 2050 cruising rpm @ 60 mph.

Gordonm

I drive an automatic all the time in my DD. I want some fun when I'm in the fun cars. Both my Cobra and Vette run hydraulic clutches. I like the feel of the hyd clutch. The Vette runs a T56 and the Cobra runs a Gordon Levy T5. Both are OD trans. I did get stuck this summer for a little over an hour in stop and go traffic and it was a little trying but still prefer the stick over an auto hands down. I like to select my own gears! Vette runs 3.70 gears and the Cobra runs 3.55. Currently in the garage I have a 72 Vette with a 496 and a TKO 600 with a hyd clutch, its going together nicely so far.

PainfullySlow

It really comes down to personal preference. If there is a concern about the 'chore' of using a clutch, stick with some form of auto. If you are worried about it now, you will likely hate it in practice.

For me, I prefer a clutch and will be going hydraulic on mine, simply because it is easier and fits with my 'modern/vintage' restomod build.

OldCarBum

Currently in the garage I have a 72 Vette with a 496 and a TKO 600 with a hyd clutch, its going together nicely so far.[/QUOTE]



For me, I prefer a clutch and will be going hydraulic on mine, simply because it is easier and fits with my 'modern/vintage' restomod build.[/QUOTE]

I know the TKO would be more fun to drive and no problem in the future with a hydraulic clutch.
I may just bite the bullet and go with the TKO600.
Are either of you running power brakes with the OEM booster?

Gordonm

For me, I prefer a clutch and will be going hydraulic on mine, simply because it is easier and fits with my 'modern/vintage' restomod build.[/QUOTE]

I know the TKO would be more fun to drive and no problem in the future with a hydraulic clutch.
I may just bite the bullet and go with the TKO600.
Are either of you running power brakes with the OEM booster?[/QUOTE]

Hydroboost is what I'm running.

cagotzmann

This is not the same transmission but this is my 1978 auto to manual conversion.

Another thing to consider how light of a clutch pedal feel do you want.

To handle the torque of the motor you will need a pretty heavy single disc clutch. With Mechanical clutch or Hydraulic it will be a heavy clutch pedal. Now if you want the feel of a C6 or C7 corvette then you will need to choose a twin disc setup. I started with a single disc.
GM6-HDSS ACT unit (735 Torque), and now I have a mcleod RST Twin disc, Higher Torque rating. Day and night difference. I will not use a single disc again for my aging body.

https://www.corvetteforum.com/forums...-corvette.html

SteveG75

Another vote for the T-56 Magnum and McLeod RST Twin Disc. I am using the stock mechanical linkage (if your car was an auto, there are bolt on brackets available for the Z-bar).

3.73 rear, 25# flywheel. Gear spread is great. 5th for 55 mph roads, 6th for the interstate.

I am also running a 496 BBC and dynoed at 413 rwhp with EFI.

If we weren't on different coasts, I would let you try my car. I ran a 5 speed for 10 years and the drop between 4th (1:1) and 5th (.64:1) was what drove me to the 6 speed.

The Money Pit

If money was no object, I would have loved a TKO-600, but my beer budget wouldn't allow it. So I went th400,....but with a full manual reverse valve body. Got the fun of a stick, without a clutch. And it'll hold all the power I can throw at it! Next round I'm hoping to tip between 560-580 horsepower.

I have yet to install my custom converter,...hope to do that in the spring. The reason I mention it, is a good converter will allow you to get the most out of your spirited launches, but still provide some cushion to the drivetrain. Dump a clutch at 5000 rpms.....stuff breaks.

lionelhutz

If you think you want an auto, then seriously consider a 4L80e with a controller.

The 0.75 OD ratio and 2.48 1st gear ratio combine to mean you could run more than a 3.36 rear gear. Both the 0.75 OD and a higher rear gear would help to raise the 4th gear cruising rpm plus it also makes acceleration more fun.

You can also adjust the shift curves to match how you drive. Until you have done this, you simply can't appreciate how much of a difference it makes. You could also add paddle shifters if you so desired.

As other comments,

The 200-4R has a 2.74 1st gear so you'd need 3.75 rear gears to match the 1st gear acceleration of a 700R4 with 3.36 gears.

The 700-R4 has a large 3.06 1st gear to 1.62 2nd gear spread. Not as nice to drive, but a "looser" converter does compensate somewhat to eliminate some of the rpm drop.

TedH

Have you considered the 4L80 (essentially TH400 with OD)? I see the ratios are slightly different but still 25% drop from 3rd to 4th/OD:

These dimensions are for a typical 4L80E but no guarantee that this is true for all transmissions.
Gear Ratio
First 2.48
Second 1.48
Third 1.00
Fourth 0.75

OldCarBum

Will a 4L80E handle the hp and torque from my 496?

lionelhutz

Yes, much better than a 200-4R or 700R4 will. It's basically a TH400 with OD.

You'd have to throw most every aftermarket hard part available into a 200-4R to make it work and expect it to last.

Personally, I wouldn't even consider a 700R4 unless you BOTH don't plan on using the go pedal much and will only run such poor tires you never have traction. It has certain limits that no aftermarket improvements can fully address, which means it's simply not the right transmission for your application no matter what anyone else says about being able to build one for high HP use.

The13Bats

Lionelhutz is on it with the automatics...

I have a lot of time invested thinking about what i want vs what is right for me, its tough, my dad was always on me about people who over build stuff they dont need or cant use, so i have a stigma,

To me a c3 deserves a stick, and to me the true spirit of the feel is lost with hyd

So for my 69 i do have that aching desire to go old school stick with it mixed with the fact as a cruiser im not all about hunting for gears,
My knees are not what they once were,
I dropped a harbor tool fright big vise on my left foot a few years ago, its never been right since,

Health or disability are real issues we have to deal with,

I knew a guy years back, older than me his life long dream, a porsche speedster,
But life delt him a crap hand no way he could use a clutch,

I helped sort out an acvw auto stick, so he could drive it, and kind of have a stick shift look,

Same with triker buddies who have limitations but want a stick, i came up with a cool pulley set up that while the peddle throw is longer the effort is very little, wint help our vettes,

My plan is when my 69 is running again drive it a lot, but i just might not swap to stick not because i dont want to but i dont want something that ruins me having a good time in the car,

I would way rather have a vette with an auto than a 4 speed vette i cant drive,

Btw,
Mr vette did a cool 4 speed handle on an auto shifter

OldCarBum

I talk to people, listen and learn. Most of the guys who are 8-10 years older than me are switching over to automatics. They are either pulling their sticks or selling their cars to start a new project with an auto. They have fought the battle but come to realize that an auto can perform as well, if not better than a stick and that age is creeping up on them and clutching around town or in traffic isn't enjoyable any longer. Having their car out weighs the need to shift. As much as I would like to build a 5-6 speed car I'm looking ahead to 5-10 years down the road. I will be collecting parts for at least another year and looking at least 2 years to disassemble and build once I start. I've had a very intense law enforcement career and had my share of little injuries along the way, but I've been lucky and I'm still running 16 miles a week and live an active life. I do feel old injuries and feel the pain while running and other activities. I've been on the fence for the last year considering a stick or auto, and for now I'm falling towards a 4L80E. It's an overdirive and geared within the parameters of my engine build. Thanks for all the help and comments. Greg