Re: Need help on 1969 L78 Nova posi
 

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I have misread the stamped in date codes on the axle tube before. What is the rear end casting date on the center section? I am wondering about the factory rear end ratio because I have never seen a real documented 1969 or 1970 L78 Nova come with anything other than a 3:55 posi rear end.

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The 3.55 was definately the most common application, but there were some vehicles that had other ratios. I personally know of two...wilma

Re: Need help on 1969 L78 Nova posi
 

Hey Tom if u were me would u look for a dated posi/3.55 for the restoration. There is a correct date BV 4.10 on eBay now

Re: Need help on 1969 L78 Nova posi
 

Considering this will be mostly a show car...I don't think you should spend more than you have to. The 3.55 posi would be easier to find and maybe a little less money...it is certainly the most common ratio found in these cars. The tranny search will be more expensive...the CX coded TH400's are a rare item. You will be very lucky to find a dated trans. that lines up with your car...if you locate a CX grab it and don't worry about the date. Hopefully it will have the 6 lug converter with it...hard to find item.

wilam

Re: Need help on 1969 L78 Nova posi
 

Tom can I call u tomrrow? Certain time? I have your phone nu
ber Ed

Re: Need help on 1969 L78 Nova posi
 

I have used this procedure in the past on Zs.

The car has to have the original transmission, or this won't work. You will also need a hand held tach similar to a RC plane prop tach.

1) Pull the speedo gear and determine the tooth count for the set.
2) Hook a drill to the speedo cable and drive the speedo to 50 MPH.
3) Measure the drill RPM.
4) Backfigure to the original gear ratio using using the drill RPM, the speedo gear ratio, and original tire size (diameter) for the car.

It is accurate enough to tell the difference between a 3.73 and a 4.10 rear ratio.

Hope this helps.

Re: Need help on 1969 L78 Nova posi
 

An easier way is look at the gear color and compare it to the chart.