How well does your car perform?  What kind of MPG do you get???

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I'm loosing it...
somewhere in this thread(or the one on 700s), someone mentioned having the original gear set out of their car from the PO, and I mentioned how to determine the ratio of that gearset by counting the teeth, or looking at the markings. Anyway, I cannot find that post now, so I'll add the pic I was looking for at the time here instead, so ya'll will know what to look for.....



Not ALL gearsets will have the actual ratio stamped on them, as this one does....but they will all have the ring and pinion tooth counts stamped(or engraved).


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Man, better use that ratio for racing only!

|UPDATED|11/21/2012 7:15:32 AM (AZT)|/UPDATED|


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"Down on the Boardwalk...

(Click image to see a larger version}

Or pullin stumps....or rock climbin...or just 'cause it's there....and it was free...

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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

3.36 would be perfect.  I wish I had done that.

So can I put a 2.64 first gear in my tranny if it doesn't already have one?  I assume the LT-1 came with a close ratio tranny.

As far as originality in your rear end.    I don't think the NCRS checks the actual rear end ratio.  I assume they just check the numbers stamped on the rear end housing.  Kinda like changing the internals of an original engine.  What they can't see they can't check.

Go for it.


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Resurrection of a thread :):) 

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1980 , ZZ430 , 3.92 rear , 700R4 2400 stall NEW EZ EFI 

Why, coitainly....all ya gotta do is change the cluster gear, and the 1st, 2nd, and 3rd gears on the mainshaft....or just swap the trans for a wide ratio and be done with it.

As far as NCRS stuff on the gear ratios, it wouldn't matter at all unless you were going for a P/V(performance verification). They check the rpm vs speed, and mileage on that, so you wouldn't be able to get away with a rear ratio change.


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

dan did you get the ratio changed. I am considering a change also and was wondering how it came out.  My 69 has 3.7 with a tremic 5 in it and I agree 1st gear is way to low, I start in 2nd most of the time but it is a bit tall. 70 in 5th is about 2360. The engine pulls good at the low rpm, and we use it for long trips.

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I have decided not to change the rear end, mostly to keep the car in its original configuration.  I just learned the it has the "Rockcrusher" transmission, so I am going to keep that too.  Had the U-joints replaced; the rear strut rods and the 4 shocks.  Also, had the inside rear wheel bearings  lubricated with a device that I got from Zip Corvette.  I am just going to live with the 3.70 rear end, since the car really runs great with the setup that the Chevy engineers thought was a good compromise at the time.  The car is a "trip" to drive, but it is just my toy, since I have a 2011 Grand Sport as my daily driver.

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Sorry but a move to a 3:53 rear is not worth it.  If you want to get your gas mileage up say, above 20 MPG, you will need to go to a Tremec 5-Speed trans and a 3:07 rear.  We have tried every variety above that (ie 3:36, 3:55)  and you struggle to get to 20 MPG.  I, too, have a '77 and all that numbers matching stuff is nice but doesn't really move the $ needle.  I would make the changes that improve driveability and save the original parts.  Gas was under $1/gallon when these Vettes were new and the big gears helped with the smogged engine performance.  I have a Turbo 400 automatic, L82 with a 3:55 rear and it races at 70 MPH.  I'm going to a 2:87 rear with an engine rebuild over this winter.  Only has 61,000 miles but valve seals and guides are leaking.

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Ralph D. Tileston

hi  I know on this site the fellas  don't like overdrives  I have used overdrive in my 49 ford to 73 chevy p/u  easy to do  takes up no room   little bit      nobody likes them.my 79 runs 3200 rpms at 60 mph hour  50 to 60 miles cost a half of tank of fuel,i have looked high and low  for a overdrive unit   no luck   contact a company that's sales overdrive  they want me to buy a new 5 speed   at 5,000 $  not going to happen,going to calf  this mouth  I will find a overdrive unit if I do  I will tell you  and you can do as you wish  good luck  dwa     p/s  can stand using that mush gas for short trip.