Need help on 1969 L78 Nova posi

[WILMASBOYL78]

Sully is correct...what tranny do you have in the car..?? 3.55 axle ratio was the norm for the L78 cars, but there were other choices. If you have a 4 spd you may want to consider some options....M20 works well with 3.55, M21 is a little doggy off the line with that ratio. Most "run of the mill" 4 spd L78's will have the M20/3.55 combo....you can't go wrong with that choice. How you plan to use the car is also worth considering...street, track, show car. Maybe you can fill us in on some more details and how about some pictures...wilma

[68-69-70Nova SSL78]

It has a turbo 400 and will be a higher end show car. I am working off the broadcast sheet which gives me alot of info but no rear end info. At least what I can decider. This is a double dash paint code car and originally hugger orange. Engine is original/solid lifter to the car but i'll need another trans and the rear end.

[1969l78]

I think CRD may mean car was a custom ordered car by dealer or a buyer. My L78 has same code and was ordered from dealer by original owner.

[68-69-70Nova SSL78]

I would think this car with the special hugger orange paint was a custom order so that could work. That is the only Code I can't decider.

[92646]

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.

[WILMASBOYL78]

[ QUOTE ]
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.

[/ QUOTE ]

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

[68-69-70Nova SSL78]

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

[68-69-70Nova SSL78]

92646 I'm on the road coming home from Indy (but not driving) and will check tomorrow. I'm really disappointed as the dates are so close but just won't work. This BU is a 3:73 nova/camaro which would also work

[69L72RS]

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.

[L78steve]

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