Question: 1980 Differential Gears:

[401KVet]

;help Would anyone know what gears are in the differential that came original from the factory.
I only do pleasure driving and have been trying to increase my gas mileage. Someone asked me about the gears, but I didn't have a clue. I'm not really thinking about changing anything on the differential, but I am curious of what I have. It is stock.

If anyone has any tips on improving the gas mileage and performance, I would really like to hear from you. I'm really not looking to get into the engine or changing the heads at this time.
But how about that differential?

Thanks to all,

 

[keith6469]

There were only two ratios offered that year. 3.07 and 3.70 ratio

 

[Hib Halverson]

the 3.70 axle was not available in 1980.

The only ratio in MY80 was 3.07

 

[401KVet]

I found a wedsite that said the (Final drive ratio: 3.55:1)
What does that mean?

 

[minifridge1138]

I believe final drive ratio is the combination of the rear differential and the highest gear in the transmission.

The lower the diff gear the lower engine rpm and better fuel economy.
A 2.7 differential will get better mileage than a 3.55 gear.
The higher the gear the better acceleration.

 

[401KVet]

This is what I found which started with the auto trans.
Does the last line talk about the gears of the rear end?
Automatic Transmission
Three-speed Turbo Hydra-Matic
floor-mounted gear shifter
gear ratios
1st = 2.52:1
2nd = 1.52:1
3rd = 1.00:1
Rev = 1.93:1
Final drive ratio: 3.55:1

 

[Hib Halverson]

I found a wedsite that said the (Final drive ratio: 3.55:1)
What does that mean?

It means the "wedsite" has incorrect information.


As for the question about increasing the mileage of an 80...there ain't going to be much you can do that's cost effective. Sure, you could replace the TH350 with a TH700R4, the automatic used starting in 82 and which has four speeds, but the cost of that mod would be so high it would literally take you ten years to recover the cost in fuel economy.

If you've got 3.07 gears now, going to a taller axle, say 2.72 or 2.59 would make the car more of a weak-suck performer than it is now.

To improve mileage incrementally, I would:

Make sure the engine is in good condition and tuned right.
Keep your tires inflated to the proper pressure
Switch to synthetic lubricants in the engine, trans and axle
In hot weather, drive with the windows up and the A/C on rather than windows down
Don't acceleration hard

 

[401KVet]

What is not correct?

 

[Vettehead Mikey]

If you're willing to sacrifice performance to get better mileage, you're driving the wrong car. Best buy a Prius.

 

[401KVet]

I have done all that. I spoked to one old Corvette guy that said putting a curve kit in the distributor could possibly give me better mileage and performance. Any thoughts on that?
Thanks,

 

[401KVet]

Never said anything about me willing to sacrifice any performance. Just trying to squeeze out a little extra mileage.

 

[Hib Halverson]

I have done all that. I spoked to one old Corvette guy that said putting a curve kit in the distributor could possibly give me better mileage and performance. Any thoughts on that?
Thanks,

That might make a difference but it will depend on what spark curve is in the distributor, now.

In any event, you're not going to see a significant increase in mileage with just that. You'll see an incremental change.

 

[401KVet]

Thank You,

 

[cleon]

Over Drive Unit

I have a 1979 with 350 auto transmission. I installed a Gear Vendors over drive unit. With several other mods it now gets 23 to 24 mph, on the highway. I have the best of both worlds, turn the overdrive off and I have performance, turn it on and I have better economy.

 

[petes74ttop]

If you call GM and give them your vin # they will send you the specifications for your Vette and a restoration guide for free.
1-800-222-1020 or 1-810-696-4800. PG.

 

[Vettehead Mikey]

Never said anything about me willing to sacrifice any performance. Just trying to squeeze out a little extra mileage.

Trying to get a '60-70-80s performance car to give you excellent economy AND performance is not going to happen unless you spend megabucks. You'll never recover the investment.

A well tuned car in stock condition can approach 20mpg if driven reasonably. What's wrong with that?

 

[401KVet]

Thanks,

 

[401KVet]

Pete,

FYI, I dialed the 2nd number first by mistake and it is no longer in service. But Bingo on your 1st number.
I have my kit on order at no charge.
Thank You,
Glenn

 

[401KVet]

I have done pretty much of what you stated. I bought my Vette this past October. It's all original down to the spark plug wires, plugs, all hoses and belts. 42,800 miles. I have changed all including a new cap,rotor,coil, and module. Changed the fluid in the rear end with Royal Purple Synthetic, and the GM additive. Changed trans. fluid and filter, but no synthetic fluid. Changed the original Cat. con. with a stainless steel hi flow. Also a K&N air filter. The engine oil I used is Valvoline Max Life Synthetic Blend, 10W40. I'm going to drive it 500 to 1000 miles letting the oil flush the engine so to speak, and changed it again.
What do you think about using a Full Synthetic in this older engine, with all of the older gaskets? I've been told that is could cause something to start leaking?

 

[petes74ttop]

Enjoying your New Corvette.

Changing wires, plugs and fluids is a good thing. The type of oil is your choice, for me, with a stock motor, conventional oil is what I use.
Glad to hear that GM still sends out the free information, with all the problems that GM is having they may not send out any more free stuff soon.
Here's another web site you might enjoy The Corvette C3 Registry you can find out some trivia, like your cars birthday, some pictures of the Corvette assembly line, and some usefull information like wiring diagrams and such.
About the milage, I get about 14 MPG.
Enjoy your "NEW" Vette, PG.