3:55 or 3:91?

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68fastback

68fastback

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68 Barracuda 8.75. I am going to spend 40% on street and 60% strip. I have 3.23 now and want to change. Is it better to go with 3:55 or 3:91's. I will be running 235/60R14 with a 360 and a 727.
 
Really the step up from 3.23 to 3.55 will not be that noticeable.Since its a 60% strip car I would go 3.91!
 
step on up to 4.10,ma put 4.10 in her bad boys. streetable enough but rude when you drop the hammer.
 
Your tires are 25.1 inches tall and turn 803 revolutions per mile. 803 x 3.91
equal 3139 rpm at 60. Kinda high. 803 x 3.55 = 2850 at 60mph. Liveable.
803 x 3.23 = 2593rpm at 60. This is assuming you don't have an OD trans.
FYI: 3.91 at 70 would be 3662. I guess it depends how tight you want to
twist it.
 
I went with 3.73, if you are going to street strip and don't want to twist it real tight you might like these

I wanted 3.91 and actually had a set of factory ones but they were pitted and with a 741 case I couldn't get anything but 3.55 or 3.73. Since I don't plan on racing it the 3.73 livened it upover the 3.23, I'm satisfied with the improvements

Oh, I have 225/70/14 tires and a standard A 833 4 speed
 
if you have a 4speed go with 3.91.. i have 4.10 with my 904 and i love the throttle response
 
i love my 3.91 but i also like the 3.55 for crusing but when you get after it the 3.91 wont let you down
 
I've got 3.91's and a 4-speed.....it's almost funny when I get on the freeway. If you're gonna just do a lot of local cruising and some strip duty, I'd run the 3.91's, but if you're gonna take some extended trips to car shows, it's gonna feel like you're in 3rd all the time on the freeway, which can get annoying.
 
Buy an extra hogshead and do a 3:23 for the road and a 3:91 on the track. There`s no way to really be happy either way unless specific gears are selected for each purpose. You don`t want to run practically the entire 1/4 mile in 2nd gear with too low of a gear and you don`t want to wear your engine out running 3000 rpm cruising the street.
 
i have a 28in tire with 4.10 and i drive 55 on the highway=)
 
aww hell go for broke get 2 chunks and set one up with 3.91's and the other with 3.55's lol
 
3.91

I have a 340 4-speed with 4.10 gears and I drive everywhere, including a 4 hour round trip on the interstate at 70 mph for a Mopar show.
 
If your mostly racing and NOT doing much hwy driving go as low as you think the combo will allow. But if you do intend on driving it on the street 3.73 is as low as I'd ever consider with those short tires. Remember tire height has alot to do with final drive gearing. Your super short 25" tires with a 3.91 gear is about like a car with 28" tires and a 4.30 gearset.
 
fishy68 said:
If your mostly racing and NOT doing much hwy driving go as low as you think the combo will allow. But if you do intend on driving it on the street 3.73 is as low as I'd ever consider with those short tires. Remember tire height has alot to do with final drive gearing. Your super short 25" tires with a 3.91 gear is about like a car with 28" tires and a 4.30 gearset.
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I never thought about that. I should try to find a taller tire.
 
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