C3 trans update
Thread Starter
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
C3 trans update
Has anyone tried to put a late model multispeed automatic in a C3 behind a reg 350 small block not a LS engine? I don't know if the bolt patterns are the same or not. Have a 77 C3 with a strong 350 with a 700R4 now thought about seeing if one of the new automatics would go in there. Thanks for any advice...
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Why would you even be interested in doing that? The 8, 10, whatever speed transmissions are being used in today's products because the engines being built have a very narrow power band. Those engines NEED 10 speeds to keep the rpm where power is being made.
On the other hand, you have a decades-old Chevy V8 with gobs of torque from 2500+ rpm up to its redline. You don't really have any need for that kind of transmission with the broad-power-band engine of the 1970's. Save your money. Oh, and study up on WHY stuff is built as it is so you won't be wishing for stuff you really don't need.
Now, and overdrive transmission swap for your 1:1 high-range tranny would be a useful thing to do.
On the other hand, you have a decades-old Chevy V8 with gobs of torque from 2500+ rpm up to its redline. You don't really have any need for that kind of transmission with the broad-power-band engine of the 1970's. Save your money. Oh, and study up on WHY stuff is built as it is so you won't be wishing for stuff you really don't need.
Now, and overdrive transmission swap for your 1:1 high-range tranny would be a useful thing to do.
Race Director
Joined: Mar 2017
Posts: 11,807
Likes: 4,427
From: Virginia
If his build thread title is any indication, @DblTrbl has a 4L80e in his turbo project. I don't recall if he bought or built a transmission controller, but the information is probably somewhere in his 20 page build thread.
https://www.corvetteforum.com/forums...strip-car.html
Adding a 5 or 6 speed manual might be easier, depending on your goals for the car. You are the transmission controller in that case.
https://www.corvetteforum.com/forums...strip-car.html
Adding a 5 or 6 speed manual might be easier, depending on your goals for the car. You are the transmission controller in that case.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,497
Likes: 6,969
From: New Or-leens Loo-z-anna
If his build thread title is any indication, @DblTrbl has a 4L80e in his turbo project. I don't recall if he bought or built a transmission controller, but the information is probably somewhere in his 20 page build thread.
https://www.corvetteforum.com/forums...strip-car.html
Adding a 5 or 6 speed manual might be easier, depending on your goals for the car. You are the transmission controller in that case.
https://www.corvetteforum.com/forums...strip-car.html
Adding a 5 or 6 speed manual might be easier, depending on your goals for the car. You are the transmission controller in that case.
As 7T1vette said....do it for the overdrive benefits.
About the hole pattern....the 4l transmission will bolt to the older engines...I think one or two holes either cannot be used or may need drilling and tapping, BUT I have read the two unused holes won't cause problems unless the engine has around 600+ horsepower.
(Other members feel free to correct any mistakes in my reply
)
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
I can think of lots of reasons for dumping the 700R4 for something better. Contact Zip, they have a 6-speed swapped C3. Maybe they could give you some advice. Since they did it it, will apparently fit in the tunnel. Bellhousing pattern is the same so maybe a crank adapter of some sort would get it bolted to your engine.
Last edited by lionelhutz; Oct 8, 2021 at 01:54 PM.
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Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
LOL, you'd probably also prefer a truck 4 speed manual with the bull low 1st gear and crappy shifting over a close ratio 4-speed with a short throw shorter so you're probably from the wrong demographic to answer the question.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
No. I would prefer the 700-R4 which is already in the car! Post #2 provides the reason multi-speed transmission is NOT needed in his vehicle.
Of course, anyone can install a 6-10 speed unit in their car. But behind a torque-monster engine like C3 vintage, it would be just another expensive toy thrown at the car.
Of course, anyone can install a 6-10 speed unit in their car. But behind a torque-monster engine like C3 vintage, it would be just another expensive toy thrown at the car.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Why an overdrive at all then? It's not needed. 700R4's really aren't a very good transmission. Big 1-2 ratio drop. Shifting 1-2 with a band which makes crappy feeling shift. The ability of it to spontaneously self destruct at a moments notice. No-one who replaces one with a different transmission ever goes back.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
You can use a 4L80e with small changes and it becomes a 6 speed. You can also get the tq converter made with the lug pattern set up for a sbc or get a diff flex plate. No one needs to know why you want what you want , or is what they think of any value..
Race Director
Joined: Mar 2017
Posts: 11,807
Likes: 4,427
From: Virginia
There are also countless examples of DIY installs on Gen 1 SBCs elsewhere on the internet. Here's a place that sells complete kits, with controllers (much like SST does for 5 and 6-speed manuals).
http://www.zerogravityperformance.co...onversion-kit/
Please post a build thread when you get going! Some of us really appreciate seeing solutions on this Forum, rather than just questioning your motives.
http://www.zerogravityperformance.co...onversion-kit/
Please post a build thread when you get going! Some of us really appreciate seeing solutions on this Forum, rather than just questioning your motives.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
This would be the 6-speed kit.
http://www.zerogravityperformance.co...onversion-kit/
If you do it, I'd like to hear how you like it. Someone from Zip posted about their 6L80 swapped C3 being way nicer to drive compared to any other 3 or 4 speed auto C3 he'd driven.
http://www.zerogravityperformance.co...onversion-kit/
If you do it, I'd like to hear how you like it. Someone from Zip posted about their 6L80 swapped C3 being way nicer to drive compared to any other 3 or 4 speed auto C3 he'd driven.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
It will make the OP happy because they have the 6-speed transmission they want. Why do you insist on making out that it's so stupid instead of shutting up and letting someone modify their car the way they want?
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,062
From: altered state
St. Jude Donor '05
Id swap from a 6 spd M to a nice 6er auto. In the powerband all the time!
Todays people on the highway arent running at 60 or 65 anymore where 3.08s are fine..even 70. Much faster
I wouldnt run a tall gear with an OD trans though its not going to behave the same as an EFI car.
A base 350 is anything but a torque monster sorry lol
Once you have a nice OD i cant seeing ever going back.
Todays people on the highway arent running at 60 or 65 anymore where 3.08s are fine..even 70. Much faster
I wouldnt run a tall gear with an OD trans though its not going to behave the same as an EFI car.
A base 350 is anything but a torque monster sorry lol
Once you have a nice OD i cant seeing ever going back.
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
LOL, agreed. If the L48 has gobs of torque then that would make an engine like the 6.2L L86/L87 quality as a torque monster, and they shipped with 8 and 10 speed transmissions. Heck, these days a Ford 2.3L 4-cylinder Eecoboost engine is as much of a torque monster as a L48, probably more.
I too would love to hear the results and impressions if it gets done.
I too would love to hear the results and impressions if it gets done.