Pulled the cover off my 71 skylark parts car, found a posi unit, 41-16. Is this a 2.56 gear ratio and did skylark in fact have a 10 bolt posi with that ratio??? Would this be a good rear end in my71 skylark with a 430 unser the Hood??? Thanks J
41 divided by 16 would be 2.56, so I guess that's what you have. Whether or not it's a good choice depends on your use for the car. If you're going to be racing it, then I'd say no. If it's going to be a daily driver, then I wouldn't bother changing it since the 430 has decent torque to get over the gear ratio. If you were to take it to the track, the chances are you'd finish the 1/4 mile still in 2nd gear (I did @ 106 in my Skylark with that ratio). You may want to focus your money elsewhere if you're on a tight budget, but when the time comes, the difference between a 2.56 and something in the 3.42 range will be enormous! What are your plans for the car?
Hey Steve, Plans for the car. Iewant it to be streetable, but it will be maing numerous trips to the track. What was the diffeernece in your times and mph when you switched to 3:42? Plan to put aluminum heads and intake on 430 eventually. The motor is extremely strong running. Should have it up and running in September, just doing the body work now. How ard is it to change the rear end gears?? Ever done it? Thank J
I still have the 2.56's in my Skylark. But when I had the GS455, I went from a 3.08 open to 3.42 limited slip (Eaton posi). But I didn't do the work. I dropped of the drum-to-drum rear and then reinstalled it after the swap was done. At the same time I added headers and a full 2.5" mandrel exhaust. I went from a 13.98 best to a 13.42 best with that change. I picked up about 4 mph.
i got a 2.56 open and my best is 14.4 at 98 and 14.5 at 99 mph. yeah this gear sucks on the track and for take off lol. but on the high way the engine rarely sees over 2500-3000 because at 2500ish your going about 70-75 mph! i'm going with the 3.42
When I ran 13.51 @ 106 in my Skylark, with 2.56's, my 60 foot was 2.30. When I was running 13.42 @ 100 in my 71 GS455, with 3.42's and 26" tall tires, my 60 foot was in the 1.87 - 1.92 range. Another thing you can do is run a gear like 3.73's and use tires to tame the ratio a bit for the highway. Put a 28" tall tire (like a 275-60-15) on it for the highway while using a 26" tall tire for the track.
i have a 72 convertable with a 430/350 combo with 3.42 gears pretty happy with the setup and the 430 aint stock:Brow: you will need traction help
Hey Andy, I figure traction would be a problem. I have a strong 350t tranny & a t- 400 tranny. Which would you use with the 430 set up???? Thanks J
i love the 350 since the detent cabel does the downshifts and can de tweaked for fast light or full throttle downshifts and lets the motor rev up like a small block my convertor is a 2200-2400 coan i didnt want much more since its a convertable and mpg isnt bad and works well with my cam setup
