Hi All,

Any chance of getting some input from those who have successfully attempted and completed this projcect; in particular those with a later model C-3. I have caught bits and pieces of similar threads on the above topic and have done searches through the archives but would still would like to talk to someone about the sanity or insanity of doing it.

Thanks!!!!!!!

 

ENCHANTMENT
I changed my '75 automatic to a 4 spd. Most people asked me how hard it was and if it was worth it. Maybe I'm just a sick puppy, but it was worth it for me.

When I was looking for a Vette I wanted a big block 4 spd car, but a good one (at a reasonable price) is difficult to find. So I found a nice clean automatic car and bought it with the intention of changing it over. I spent the next couple of years looking at other 4 spd Vettes and picking up conversion parts at swap meets.

Once I had all the necessary parts I ripped out the automatic. I've switched over other automatic cars before, but this was my first Corvette and it was definitely more work. Especially, pulling the dash and steering column to hang the clutch pedal assembly. Also, I have pretty good access to a machine shop and used Chevy parts so I only had to worry about Corvette specific parts.

Aside from basics like pulling the auto itself, related linkage, cooling lines, and spilling tranny fluid all over the floor; other conversion "highlights" include:
-Remove steering column and drivers-side dash to install clutch pedal assembly
-Weld on bracket for clutch linkage cross shaft (located under the brake master cylinder)
-Replace auto tranny and exhaust pipe mounts on crossmember with 4 spd ones (this is where the rubber tranny mount attaches)
-Remove exhaust pipes and get the car jacked up as high as possible (makes things easier to work on)
-Fix all the other things you find that need fixing

A few tips:
Get a GM Assembly Instruction Manual (AIM).
Do you currently have a 400 turbo? Find a good BW Super T-10 with 400 turbo style output shaft. You won't have to modify the drive shaft.
You could consider a 5 spd of even a 6 spd, but the mods would be much more extensive. Other guys from the forum can help you here.
Chevy makes two size of bellhousings; the "smaller" one will only accommodate a 10-1/2 " style flywheel ( 153 tooth ring gear); the larger one up to an 11" style flywheel (168 tooth). Also, your automatic starter housing "nose" may interfere with the bellhousing. I did a little grinding in the bellhousing to make mine fit.
Check balance on flywheel and clutch before installing. Don't go "cheap" on clutch/pressure plate.
The hole in the tunnel under the automatic shifter is different then the one for a 4 spd shifter. Don't worry about it, just cut a slit in the rubber cover for the new shifter. Use a Hurst Comp Plus shifter, it work's with the standard corvette shift plate. Good Vette shifter's are expensive and I don't think they work as good.
Don't forget all the oddball stuff like: speedometer gear/cable, neutral start and back-up switches, and who know's what else.

Have I talked you out of it yet?
Bottom line: If you are worried about matching numbers or must to pay to have the work done.....start shopping for a 4 spd car or learn to enjoy the automatic. If you have experience doing this kind of stuff (pulling engines, tranny's, etc.), like skinned knuckles, have lots of rags and hand cleaner, and a burning desire to speedshift, go for it.

75rat

PS: E-mail me if you have more specific questions.

 

75rat did a good job covering this. I also went from a 400 to a 700 then a T5 in my 75 vet and really like the standard alot better. Changing the pedals is the hardest part. The actual installation is easy. If the driveshaft needs shortening it is a cheap $40 or $50 deal. Takes a drive shaft shop an hour or two. Go for it but I would definitely go with a overdrive. Even a T5 will stand up if not power shifted.

 

Norval, I spoke to you a long while back before I bought and installed the 6 speed, but I never asked why you decided to go to the manual transmission from the automatic. For me, it was the shifting and lost desire to drag race more than cruise distances, but you have a drag car with tons of horsepower and I would have thought you might want less gears, like a powerglide. Was it for the overdrive, more power to the ground and shifting?

 

Gary,

I was impressed with your T-56 conversion, (under statement!). Why did you go with the mechanical clutch linkage as opposed to the hydraulic slave that is usually associated with the T-56? Look forward to seeing a web site on the conversion.

Good Job!

 

ENCHANMENT,

Thanks! I will get the website up soon! Originally, my car was a 4 speed car, so the migration back to a standard was easy. I left the clutch pedal in the car, when I went to the automatics (400&700R4) for reasons you already know (PITA to change). In checking with people like Norval and finding out how it would be possible to go with the hydraulic clutch set up, I started looking for and found a bunch of used factory T-56 transmissions, for $1.3K, to buy, but when I went to Forte's site and found out that no one he knew ever put his converted transmission in a Vette, I got interested. I already had all the old manual pieces, so I figured I would see if it would be a swap others could do relatively easy. It was not that bad of a job. I must say that I liked the automatics, but I missed shifting.


[Modified by GWHITE75, 3:34 PM 1/23/2002]

 

Gary,

When you were originally looking for a T-56 (prior to Forte), where were you looking?

Thanks!

 

I replaced my TH350 in my 76 with a Richmond 5 speed. Not too bad, and the only real difference than installing a 4 spd is that the rear tranny mount has to be modified (instructions come with the tranny). It does involve some cutting, welding, & grinding of the TH350 mount.

A couple of things to add to 75rat's post:
1) If your going to use the factory mech linkage, make sure your engine has the tapped hole for the crossbar pivot bolt.
2) 76 and later vettes have a solid steel floorboard. You'll have to cut a hole in it for the shifter. I bought the factory rubber boot and installed it into the floor. Worked out pretty good.
3) I didn't fully remove the dash to install the pedal, but it is a PITA. I loosened the driver side, removed the steering column, and then (laying on my back under the dash), removed seveal brackets that are between the steering column and the brake mount. Then I fed the brake assy. down and out of the dash. Installation is reverse. Took two afternoon and just a few swear words. :cuss
4) I also used a Hurst shifter and it fits the slot on the factory console plate for a stick. Comes right up through the leather boot. Most people don't even realize that the car didn't come as a stick. :)

http://temp.corvetteforum.net/c3/greatwhite/

 

Gary, why did you have to cut the crossmember? There was no other way to mount it up in there?

Thanks! :smash:

 

I replaced the TH350 with a R.O.D. 6-speed in my 1979. It's just like the guys say.......I LOVE mine!
:yesnod: :chevy :chevy :yesnod:

 

GWhite75 I went to the standard because I blew 3 700R-4s and 4 torque converters in one summer. It bacame a weekly chore of pulling the trany. Got very good at it. I also wanted to feel more like I was driving the car, I was tired of the high revs all the time with the loose converters. The lock on the torque converter was constantly slipping if I passed with too much throttle. I could take a 3500 stall converter to 5000. I am never sorry for going with the standard and wish I had done it long ago. I really like my hydraulic clutch for pedal effort, simplicity in installation and I didn't want that mechanical linkage interferring with header removal, which I do alot. I am not a drag race nut. I like driving powerful cars but I don't beat on them. I also removed my slicks when I went standard to keep things from breaking.
Price wise the tremec is a good deal. It is just as strong as the T56 and 1/2 the price. I often just use 1,3,5th.

 

Norval Your car has been a good project for you and a benefit to us on the forum and I appreciate your knowledge. You really had me going to the 5 speed, which I try to recommed to others, because I think it would be more suited to some who don't want to start cutting up their vehicles. I wanted a bunch of gears and I liked the ratios in the unit I installed, plus I wanted to see if it was possible to get one of these aftermarkets in a C3 without too much hoopla.

ENCHANTMENT I started looking on a website, local to Houston, called hotrodgossip, where I found two at the time, one was out of a 2000 Z and he was selling all pieces, except the hydraulic mechanisms for $1200. Some other places:ranchochevy.com tracyvette.com ebaymotors.com darkhorseperformance.com and there was a local Camaro yard outside of Houston that had some. These units are factory GM and would need the hydraulic clutch system, T-5 bellhousing or scattershield and a modified flywheel/late model clutch system. They are not very hard to locate. You can look in the classic auto traders to find other places. I think there are a couple of places in Florida that sell motor/trans combinations, but will separate them for the right price.

rainman69 I cut the crossmember originally, for the installation of a turbo 400 automatic, but I wished I would have cut the thing years before, because any transmission swap is made tons easier. I used to run a Doug Nash 5 speed (now Richmond Gears), and had to muscle the thing in and out when the crossmember was fixed. I put this transmission in with the motor and have yet to pull it out of the car. I can see that it would not be possible to get this one in or out, without a removable crossmember. Another advantage to a custom built crossmember: It can be built to eliminate the holes for the exhaust pipes. I built mine above the pipes. Disadvantage: Parking brake relocation.