3:55 gears on the street

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Clamcake

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I am currently working to swap out the rear gears in my Duster with an 8 1/4 from a 2:76 to a 3:55. I have a 360 (bone stock) and a 904 tranny, 15"x8" rear wheels with a 255 60r set of rear tires. I want the car to be quick from light to light but still do 60 mph @ about 2600 rpm. Does anyone have experience with a similar swap? Any suggestions? I appreciate your feedback. Thanks!
 
255/60's on a 15 inch rim? That is right about a 27 inch tire. IDK how much bigger he can go.

3.55 are good for the street.
 
I have 255 70 15 on my dart and they r 28.95 inches tall. Had 3.55 with detroit locker and went to 3.23 Tru Trac for street driving.
 
Clamcake said:
I am currently working to swap out the rear gears in my Duster with an 8 1/4 from a 2:76 to a 3:55. I have a 360 (bone stock) and a 904 tranny, 15"x8" rear wheels with a 255 60r set of rear tires. I want the car to be quick from light to light but still do 60 mph @ about 2600 rpm. Does anyone have experience with a similar swap? Any suggestions? I appreciate your feedback. Thanks!
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Just went for a cruise and the dart is right where you wanna be 2600= 60mph
4500=90mph

This is a 340-727 car. I don't know how much different a 360 would be?
 
purpledart said:
Just went for a cruise and the dart is right where you wanna be 2600= 60mph
4500=90mph

This is a 340-727 car. I don't know how much different a 360 would be?
Click to expand...

Your speedo is off. Did you change the gear in the trans to match your tire size/gear ratio?

With a 255/70/15 and a 3.23 you are around 78-69 MPH at 2600 rpm and 120 at 4500 rpm.

http://www.kabamus.com/garage/gears.html
 
with 355's and 26 inch tall tires on My 66 coronet...I turned 3000 at 65......with 28 inch tall tires on My Bee...I turn 2700 at 65.... go with the 355's and experiment with tire height...easier than rearend swap..26 inch on My current Demon is obviously the same as coronet...Super gears as far as I'm concened for a street car and I wouldn't go 323's ever again..
 
3.55's behind the 318/340 6pack marriage in the Fury with 225/70/15 tires... don't know the rpm, but I can still make it from Baltimore to Carlisle 2x in one weekend on one tank of fuel..(that's 8 hrs of driving total)...and yes, it woke the land barge up a good bit compared to the 3.23's...
 
Speedo Gear is correct from the chart on this forum!
It's the chart from Tony

30 tooth purchased from member Locomotion
 
Actual tire diameter and converter slippage will vary the RPM and speedometer reading.
 
I changed my gears from a 2.44 (yes you read that right LOL) to a sure-grip 3.23 behind a 360 with a 727. Made the car a lot quicker but I easily could have gone with a 3.55 setup. It wouldn't have hurt the rpm at 60mph much. I would say go 3.55, you won't regret it, great all-round gear, fun light to light without losing out on highway cruising. JMO
 
67cuda360 said:
I changed my gears from a 2.44 (yes you read that right LOL) to a sure-grip 3.23 behind a 360 with a 727. Made the car a lot quicker but I easily could have gone with a 3.55 setup. It wouldn't have hurt the rpm at 60mph much. I would say go 3.55, you won't regret it, great all-round gear, fun light to light without losing out on highway cruising. JMO
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Prolly would be good I just wanted a little better mpg cruising. I am ordering some new 3.55 or 3.73 haven't decided for my other chunk with the bad 3.55s in it.
 
3.91's and 27 inch tall tires, it turns 4,000-to 4,500 on the freeway but cause I still go 80 mph plus, lol

the 340 seems to like it, now mpg, Ha Ha. $20 goes too quick.

3.55 would been better but it took many years of 70 mph speed limits for traffic to speed up. 5--10 years ago I was passing everybody going 75 to 80..now I can go 80 and get past every 5 miles.

3.23 ugh, yeah they are nice but only at 75 mph plus, around town you are hurting, at 45 mph the 3.91's feel just fine and in 2nd gear it has a really good kick

Quieter mufflers really help to make 4,000 rpm feel not so rough
 
purpledart said:
Just went for a cruise and the dart is right where you wanna be 2600= 60mph
4500=90mph

This is a 340-727 car. I don't know how much different a 360 would be?
Click to expand...

Engine size makes no difference. It's about tire diameter and gear
ratio as far as I know. Slip thru the tranny may have some effect.
 
Clamcake said:
I am currently working to swap out the rear gears in my Duster with an 8 1/4 from a 2:76 to a 3:55. I have a 360 (bone stock) and a 904 tranny, 15"x8" rear wheels with a 255 60r set of rear tires. I want the car to be quick from light to light but still do 60 mph @ about 2600 rpm. Does anyone have experience with a similar swap? Any suggestions? I appreciate your feedback. Thanks!
Click to expand...

ive run everything from a 276 gear to a 456 gear on the street with a 28" tall tire, 3spd, and even on the hwy.

in the end, i found that the best gear for me to run on the street is a 373 gear with a 28" tall tire, around 100km/hr close to 3000 rpm, and yet from a light it launches like a bat outta hell.
 
So much good feedback from members who have forgotten more than I will know about this stuff. Thank you all, I will try to post pictures if I can figure that out. FABO has been a great resource, I hope I can be as much help someone some day.
 
Blue87D100 said:
Check this out Gear-Speed Calculator Program

Looks like you will be around 2600 for 60 mph. You could always get a taller tire for longer trips to bring the rpm down some.
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I only have the small Crager 14" rims, so would 225 75 14 work to keep the rpms down? LOL. I mean people are talking about 27" tires. Cripe! So for 3.55 gears, what would be the minimum size tire I could get away with without winding out?
 
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