3.23 or 3.55 behind 71 340 727 Auto???

Posted By: fireeng

3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 01:52 AM

I'm finally getting my car done. I have my choice of ratios as I have one of each in my stcok pile. I'm building the car mild enough so my wife could drive it if she likes. I'm leaning toward the 3.55s so its a little quicker off the liune but I'd also like to drive at 65 mph for 40 miiles or so every once and a while. I've been out of the game since I was a teenager so I could use some knowledge on how these ratios differ. Thanks....

Posted By: derekeh

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:04 AM

I would lean towards 3.23.... but they arent that difficult to swap out. Try both!

Posted By: Neil

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:05 AM

I like 3:55's on the street, but I wouldn't go with a tire shorter than 26" in the rear if you want to hit the highway for any great distance.

Posted By: fireeng

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:05 AM

I didn't even consider tire size. What size tire is 26" tall?

Posted By: ademon

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:06 AM

3.55, especially if going with a tire taller that 26"

Posted By: Neil

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:08 AM

Quote:

I didn't even consider tire size. What size tire is 26" tall?

235-60-15 are advertised as being 26" in diameter.

Posted By: fireeng

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:11 AM

235-60-15 are advertised as being 26" in diameter.

I think those are in the ball park of what I would use. Do you think the 3.55s will be really winding out for that highway ride?

Posted By: thedriver

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:16 AM

http://vexer.com/automotive-tools/speed-rpm-calculator

this is a fun tool to help.

Posted By: Mopar_Country

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:24 AM

Depends on what your doing with the car, if you want a little strip time then 3.55's.

Posted By: Challenger 1

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 02:27 AM

Quote:

3.55, especially if going with a tire taller that 26"

My 440 car with 28" tires has a 3:54
My 340/727 with 26" tire has a 3:55

I think they are perfect for the street and I can tell the difference between 26-28" tires.

I drive my 340 car with 26" tires on the highway all the time.

It tachs about 5000 rpm at 120 mph with 3:55 and 26" tires. speedo says 135 but the GPS said 120mph at 4900+ rpms

Posted By: joewhite440

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 05:10 AM

Quote:

Quote:

3.55, especially if going with a tire taller that 26"

My 440 car with 28" tires has a 3:54
My 340/727 with 26" tire has a 3:55

I think they are perfect for the street and I can tell the difference between 26-28" tires.

I drive my 340 car with 26" tires on the highway all the time.

It tachs about 5000 rpm at 120 mph with 3:55 and 26" tires. speedo says 135 but the GPS said 120mph at 4900+ rpms

Best ratio for street use. That is why they are hard to find used. If you were going to also race the car. I would have said 3:91's and they are even harder to find used.

Good luck and glad you are "back in the game"

Joe Sr

i

Posted By: JoesMopar

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 06:45 AM

I'm running a 3.55 behind a 440/727 combo on my '69 Charger with 295/50/15 tires. I run about 3200 RPM @ 70mph. The next car I'm doing is going to have a 3.23.....

Posted By: fireeng

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 03:55 PM

Thanks for the input. I am going to try the 3.55s and see how it goes.

Posted By: 68bb

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/24/10 11:51 PM

I put the 3.55's in my 70 dart 318 4 speed over the winter and am very pleased.Doesn't feel at all bad on the highway at 65 - 70. Had 3.23's in my 68, but I like these better.

Posted By: Magnum

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/26/10 02:39 AM

Have you considered an overdrive?
Any choice you make will always be a compromise.
A highway gear is high 2's and a drag gear is 4 something.

If it's a restoration or if you don't mind spinning the engine high or enjoy driving in the right lane with everything passing you, disregard.

Posted By: YO7_A66

Re: 3.23 or 3.55 behind 71 340 727 Auto??? - 08/26/10 02:48 AM

I have ran both 3:55/26" tires and 3:91/27" tires and I like them both with my 340/727 Challenger. I don't usually run 70+ (except WOT runs) but up to 70mph cruising speed is fine with either of these combos.