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A big hey to the C3 page which I don't venture to often enough.
I have a neighbor who is a buddy of mine looking to build his 79. He's a younger guy trying to piece it together on his first serious build. We all remember being there.
He's looking into setups to get a 9" into it with a quad link setup and I don't know what the heck he found but he's telling me it's some 6k product which would then cost 5k to have welded in.
Im sure all your eyebrows are going about as far up as mine did hearing that.
What are some bullet proof options for a street/strip setup on these cars? I guarantee he'll be pushing +1k eventually. And maybe I'm just ignorant and that's what things cost for C3s, but 11k just to get a large ring and pinion and to plant the tires seems nuts.
It looks like THIS was the one he was looking at and had been quoted by phone the $6500 as including and whole assembled rear end with suspension, brakes, axles, etc.
Some questions and observation- no recommendation on a build type or builder- that requires a good amount of homework or the learning curve will be very expensive.
Is this car in the North Haven- Wallingford area?
Corvettes were not really designed for drag racing, they are road cars. They failed at the track 50 years ago, but can be built to handle a lot.
Before selecting a differential you need to know a little more, like power, traction, trans, usage. Building of one type may not work for various reasons. The math has to add up for the best option.
I sense a tight budget here, which is certainly something to think about however quality today is not cheap and not always easy to find. Some here know first hand what a under cut build ends up costing as you have to do it again.
If you require a strong differential you need to address the other areas South of the Flywheel or you will be calling AAA a lot. The term Bullet proof has become nothing more than a sales pitch to capture those without a full understanding of these cars and the limitations of the IRS and some conversions. Looking at a website and not "seeing" the differential past the hype will cost you in the long run as nothing is bullet proof. Some are very strong and last with a lot of abuse but all items can be broken.
If you stay with an IRS and have more then 500hp you better address the outer axles as they will snap. Same for Driveshaft and yoke sizing, frame gusseting, frame condition, shocks and spring. If you go solid 9" it's good but gives up road use - which may or may not be a concern. I have been around these cars since the mid 70's and there was always a debate on the 12 bolt Chevy vs the 9" Ford. Some points have merit others do not. Some of the conversion kits are very nice, the 9" Factoid shows is very impressive. The modified 10 bolt not so much. This is just my opinion given the fact I have some exposure to vette work.
Here is how I would rate some diff's common today for the 63-79 vette. Again just my opinion. Trying to pinpoint a level where a diff will fail is not easy and has many things affecting it. Usually smoke and mirror reasoning is used when peddling some builds.
Stock 10 bolt- good for a street car in most cases. Most basic level of build and least expensive
Blueprinted 10 bolt. Some mods to add strength and good for a nice modified street car to about 450hp and not a lot of track use
Modified 10 bolt as shown on some web sites. This type I really find interesting and if you do your homework well you will see through the hype to see the real deal. If not, well what can I say.
Super 10 bolt- a real one not a knock off - some in cars with 700hp although I feel more comfortable in the 550-650 range.
12 bolt 1350
12 bolt 1480 and 9" are about the same at this level. There are various ways to build them, some have converted 9" to an IRS as well. Very careful research is required at this level.
DANA 60- pretty strong but finding the one with a similar housing is not easy and expensive if you do.
Last word of caution- be careful around that rabbit hole it can be very deep. Some of these builds cost more then buying 2 new 79 vettes or a car better suited for drag racing in a tighter budget build.
I can't quote budget as I don't know other than it is a car from his family and he intends to build and keep it for life. And there, too, is a big question because I know he's not sure yet what to build for an engine. I think the parts list seems to be over the top when a used LS and turbo would get him competitive for cheap to start and be easily replaced when blown up. I had suggested alternate frames for lower cost and weight, but the Corvette is "it."
If your friend is Mike then I know him and he knows my son well and his built car
You have to start with the engine and work from there. It's a mistake to do it the other way.
Lets say you want a 9" but you are building a 350hp engine- way overkill and not needed. Likewise if you're putting in a 500 hp engine and plan on pushing the car hard, then a stock built diff is going to turn into instant junk if the car reaches full potential.
Right on the money about Mike. Yeah, I have mentioned setting a goal and building a matched engine and drivetrain combo but that hasn't taken root yet. If we can help him save money and skip some mistakes along the way I'll feel better about it. Not that I know the kids around here, but who is your son or what car is his?
Oh to be young again! But I had some pretty big time racers in my area that helped me alot in exchange for helping them out. I can't imagine how much money I saved that way.
Gtr is absolutely correct start at the front and work back.
The 4 link and the 9" shouldn't cost that much. The labor will get you every time.
If he wants to reduce the cost, needs to get familiar with welding it himself. 4 link kits are about $1,100. Aluminum 9" solid rear about $1,700. Welding it in yourself, priceless. As welding projects go, it's not that difficult.
My 4 Link uses an 8.8 with 9" axles. They are known to be good for 1k. And very adjustable for traction.
There are some setups here to make me jealous. I'm going to see how far I can go running C6 Z06 cradle and built diff/trans on my C5 with coilovers and delrin bushings to try to plant the tires and keep them from deflecting.
Rear End Options for Drag Setup
