Best final Gear Ratios and tallest gears available

[392 Cuda]

I'm pretty close to having all the parts for my 8 speed swap. Looking at the final ratios, it seems 1st gear will be about 16.7 with my 3.55.

I have read that 10 is best. Is that true? What is the tallest gear I can find for a 489 rear? (3.23, 2.76?)

I appreciate the help as always!

[1 Wild R/T]

Kinda depends on what your doing....  16.7 is great, if you are planning to join the Rubicon guys... But on the street you'll be pulling gears 30' out...

2.76/2.94/3.23  are your options for the 8.75

[GoodysGotaCuda]

Are you sure that it will even use 1st? Most 8spds start out in 2/3 unless you have it in some sort of sport mode, where you'll have to rely on a really sticky tire more than the axle ratio. 

[RUNCHARGER]

I ran 4.56 with a 2.66 first. Good for burning rubber but tough to get off the line. That comes out at 12.2. I wouldn't go deeper than that unless you're running slicks on the street. On my Viper though the only thing 6th is good for is 80MPH and up for fuel mileage. I'm usually in 5th when the police are around unless it's really flat. It has a 3.07 with a 2.66 first and it works pretty good off the line but it has butt loads of torque and is lighter than an E-body. If I had that trans in an E-body I would probably try a 3.73. That comes in at a 10.

[gzig5]

With an automatic I wouldn't be worried about first gear. It will shift itself when needed and get the car out of the hole nicely.   Running a 2.xx final ratio and a 0.50x overdrive in top gear is going to have the engine rpm down in the weeds lugging the engine, isn't it?  That's the advantage of the OD trans is you can run a 4.xx final without buzzing the engine.  If it were a manual, I'd pay more attention to first gear.  My BMW M5 six speed manual has a 4.5x first gear and 3.45 final. First is good for about 25-30 mph but it moves that 3900 lb car out of the hole nicely. I just start out in 2nd when I get tired of shifting.

[Chryco Psycho]

My Duster was 3.07 1st gear [manual trans] with 4.30 gears about 14-1 in 1st gear , I could lift the front tires at will & cover 60' in 1.40 seconds , yes this was a street strip car

[392 Cuda]

I appreciate the advice. It sounds like 10 isn't a hard and fast rule.

I may just see how it reacts to the 3.55 for now, or swap in a 3.23 I have in a box somewhere.

[gzig5]

Definitely give it a try first.  I don't think you'll see a huge difference from 3.55 to 3.23.