1978 C3 gearing questions
Thread Starter
Cruising
Joined: Jul 2015
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1978 C3 gearing questions
Hello, all my life i have always loved corvettes and now i am finally going to get one! It is a 1978 fastback C3 with the small block 350 and 4 spd manual. It has the 3.36 final drive ratio and i am wondering what is the lowest gear i can fit in the rear of the stock axle.
I would like to have my rpm be between 1,500 and 1,800 at 60 mph for fuel economy on road trips so i would need a 2.00-2.35 ratio axle in order to achieve this since 4th gear is at a 1.00:1 ratio. Will anything in this range work/fit in the stock rear end???? Thanks!
I would like to have my rpm be between 1,500 and 1,800 at 60 mph for fuel economy on road trips so i would need a 2.00-2.35 ratio axle in order to achieve this since 4th gear is at a 1.00:1 ratio. Will anything in this range work/fit in the stock rear end???? Thanks!
Thread Starter
Cruising
Joined: Jul 2015
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Performance wise it is great, the only problem i have is that at 60 I'm spinning about 2,700rpm which is pretty high. I do a lot of road trips and i would love for the vette to get used instead of just sitting in my garage.
P.S. I have read a ton of your posts and you seem to be very knowledgable, thanks for your input.
P.S. I have read a ton of your posts and you seem to be very knowledgable, thanks for your input.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Get yourself and overdrive transmission. This is the only way to drop the ratio that low. The lowest you can go is a 2.73 and that was never factory installed. 3.08 was the lowest factory gear set.
Thread Starter
Cruising
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2.73 would be better but i would be at about 2,200 which is still pretty high for a v8 on road trips.
Thread Starter
Cruising
Joined: Jul 2015
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I really don't like autos unless you are referring to a 4+1 manual that i don't know of, which is very VERY possible since i don't know chevys super well. What is the model of tranny if it is a manual with OD?
Only manual with OD i know of is from the older volvo's
Only manual with OD i know of is from the older volvo's
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Thread Starter
Cruising
Joined: Jul 2015
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Is this a good price for a full kit? I think this would be a great option. Thanks
http://www.ebay.com/itm/Tremec-5-speed-TKO-600-Transmission-Corvette-vette-C1-C2-C3-kit-/291404404603?pt=LH_DefaultDomain_2&hash=item43d90e577b&vxp=mtr
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I have put in several TKo transmissions in Vettes. I have one coming in my garage in about 2 weeks to do. This is definitely the way to go. I have never had anyone be disappointed in the TKO. I had one in mine for a few years. Liked it so much I went to a 6 speed with 2 over drives.
Thread Starter
Cruising
Joined: Jul 2015
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I have put in several TKo transmissions in Vettes. I have one coming in my garage in about 2 weeks to do. This is definitely the way to go. I have never had anyone be disappointed in the TKO. I had one in mine for a few years. Liked it so much I went to a 6 speed with 2 over drives.
Also, what kind of fuel economy do you get on the freeway?
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
I am thinking - without knowing all of your cars details - that you would be happier with the 5 speed. If you have a 78 with ~175 horse power, you may not get much use out of a 6 speeds double overdrive. You need good torque at low RPM to use it. If you were to pick a 6, they come with different ratios and you may want the less steep 6th. I love my 6 speed, but the fuel injection makes it work in my application.
Good Luck
Good Luck
Thread Starter
Cruising
Joined: Jul 2015
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I am thinking - without knowing all of your cars details - that you would be happier with the 5 speed. If you have a 78 with ~175 horse power, you may not get much use out of a 6 speeds double overdrive. You need good torque at low RPM to use it. If you were to pick a 6, they come with different ratios and you may want the less steep 6th. I love my 6 speed, but the fuel injection makes it work in my application.
Good Luck
Good Luck
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 14
From: Mobile Alabama
That is a whole different animal. I am running a 5.3 with a TR6060 and it works well. The double overdrives were designed with injected engines in mind. If you are going the swap route, I would defiantly go with the modern trans.
Melting Slicks
Joined: Jun 2011
Posts: 3,116
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My MPG Highway test run was @ 115KPH ( ~ 72 MPH ) 27.8 MPG (23.4 US)
My Engine is a stock GM ZZ383.
Thread Starter
Cruising
Joined: Jul 2015
Posts: 13
Likes: 0
Thread Starter
Cruising
Joined: Jul 2015
Posts: 13
Likes: 0
