Gear Ratio upgrade for 69 GTX

I just got a 69 GTX it's 440 4 barrel with a 727 auto trans. The car has 3.23:1 rear end gear ratio. I bought it knowing it had a rear end noise. The repairs require basically redoing most the rear end. My question is should I keep it the stock 3.23 or increase it?

The shop where the rear end is being done suggested leaving it be. He said there is not enough noticeable difference from the 3.23 to a 3.55 for the money and going to a 3.73 or bigger would make the car unbearable on the highway.

I don't plan on doing a ton of highway driving and do not necessarily want a car with no guts when I mash the pedal. At the same time, I don't want my muscle car to be restricted to Highway speeds of 55-60 mph.

well 323 sounds like a good gear if you want to run the speed limit on the highway i had 355 and could but it was running 3200 or so at 70

With a 440 and an auto 3.23 is a good choice. If you want better 1/4 mile performance, then 3.55 or 4.10 for sure, but as already mentioned freeway driving won't be as nice.

Here's a pic I took while on a lil highway cruise in my Duster. 360, auto, 3.91's. Runs just fine.

You also need to consider the stall speed on your converter. If it's to high and you're geared to high (low numerically) then you might generate a lot of heat in the trans and burn it up

I'd run the 3.55's as well. Oh, and welcome to the board.

i was gonna say 391 with some tall tires

Yeah, 3.91 and tall tires should do the trick.

Go to Randy's ring and pinion and use the calculator. Sounds like you have an idea what you'd be comfortable with. He used to have a 3:73 ratio, but I'm not sure what case it was for...FWIW I have 3:55's in my GTX. nice difference from the 3:23's it had.

A old rule of thumb was that for every step up in gear you picked up a tenth in ET at the drag strip...3.55 - 3.91 -4.10 - 4.30 -4.56.
The car's that didn't pick up a tenth usually needed a little larger carb to take advantage of the steeper gear...
For a street car that doesn't see hi-way speeds a 3.91 - 4.10 is a fun gear ratio to have .
There is a noticeable difference between seat of the pants feel between 3.23's and 3.55's. IMO
For a stone stock 440 I'd use 3.55's

I have used 3.91s in my old 68 beeper with a mostly stock 440 and 727 with a 3k conveter. The car had a 275-60-15 M & T street tire and was great to zip around town with. That 440 had 915 heads, the old .509 hyd cam a edel. torker with a 750 DP holley. It was a very mild setup, highway runs were ok. The RPM is liveable unless your really pushin the speed limit for a long distance.

3.23=gas mileage
4.56=get there in a hurry in a short distance

I love my 3:23 and 28" tires: 2400RPM @ 60mph.:yes:

Still has plenty of punch to burn the tires at a stop light too.:grin: