3.55 vs 3.91

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mopowers said:
How do you plan to put more than 28" tall tires on it?
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I looked again and I was actually wrong, my tires are just over 27 inches tall, but yea, not going to fit much more than 28 anyways, forgot about that.
 
Only you can decide what is right for you, I put in 27" tire and 60 mph for the following calculations.


2.74 - 2100 rpm
3.23 - 2475
3.55 - 2700
3.91 - 3000
4.11 - 3150
4.30 - 3300
4.56 - 3500
 
!m putting together a 3.55 right now. Tired of 4.10s on the highway. With close to 600 ft pounds of torque I doubt takeoff will suffer much.
 
With 600 ft/lbs I wouldn't even think about anything higher/shorter than a 3.23.

I've got a 496" stroker in my '60 NewYorker but the car drives so much better more pleasant with 3.23 gears than 3.91 gears.
 
I am going with 3.73s in my Signet- compromise between to ratios
mild 340 Not on road yet though
 
DartVadar said:
Because currently the car isnt the funnest to drive, the 2.76s suck the life outa it with my engine combo, just dont want the 3.55s to only be a marginal increase in performance.
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I went from a 7 1/4 2.76's to an 8 3/4 3.55 suregrip.

Let's just say the look on your face will be priceless, the first time you mash on it.
 
DartVadar said:
I looked again and I was actually wrong, my tires are just over 27 inches tall, but yea, not going to fit much more than 28 anyways, forgot about that.
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There are 3ways to get the taller tires on your car.

1. easiest. Buy front shackle spacers.

2. inboard kit using RMS kit. It allows you to move the rear back 1.5"

3. Best way, hardest most expensive way as well. Stretch the quarters.
 
sireland67 said:
Only you can decide what is right for you, I put in 27" tire and 60 mph for the following calculations.2.74 - 2100 rpm3.23 - 24753.55 - 2700 3.91 - 3000 4.11 - 3150 4.30 - 33004.56 - 3500
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I think that's off a little. I can tell you from first hand experience with my 65 Valiant. It had 28/11.50/15 E/T Streets with 4.30 gears and a loose 3000 converter. I drove that car literally everyday back and forth to work on the interstate about 6 miles one way. Kept my big toe on the gas at 55 MPH and it was a tad over 2500. Spent most of its time in converter slippage, but the car was very light, had lots of gear and a BIG trans cooler.
 
SOunds about right rusty and with a tighter more efficient convertor that would improve.
 
DartVadar said:
I am looking for some new gears for my dart, and am not sure what would be best. I have a rebuilt 360, comp xe268 cam eddy heads etc, so its got some power. A factory torque converter (want to change out soon) and a 999 trans with a low first gear set, and 28 inch tall tires.

I know I need at least 3.55 rear gears in the 8 3/4 to make the combo even work at all, the 2.76 gears are doing nothing for me in the "seat of the pants" off the line. I know you can get 3.73 gears but were not factory gears I don't think. So that leaves the 3.91s. I typically only drive in the city, rarely up to 60 mph. I am kind of leaning towards the 3.91s at this point in time. For city driving without much highway (if any) and runs at the track would 3.91s be good? Or would my engine be revving really high all the time?

I also would venture to guess that there would be a substantial difference in acceleration going from 2.76 to 3.55s or 3.91s?
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I'd run a 3:73 or 4:10 with an adjustable snubber for street/strip use, your choice.
Best guess is you have about 400hp, an 8"wide tire will hold if you've got the suspension dialed in.
Tire size would be what ever hooks best on the track and you can get under there.
I'd lose that stock convertor immediately and go with a 2200 to 2600 stall for
a decent all around street/strip package that can be driven daily without a bunch of headaches.
A trans cooler is a must.
 
I had 3.91s with a 318 and a 4 speed. It would rev 3000 RPM at 65-70MPH. I could also slow down and make a left turn and stay in 4th gear if I wanted to. Just an example. I had stock 14 inch rally wheels with stock tire size.
 
longarm said:
I'd run a 3:73 or 4:10 with an adjustable snubber for street/strip use, your choice.
Best guess is you have about 400hp, an 8"wide tire will hold if you've got the suspension dialed in.
Tire size would be what ever hooks best on the track and you can get under there.
I'd lose that stock convertor immediately and go with a 2200 to 2600 stall for
a decent all around street/strip package that can be driven daily without a bunch of headaches.
A trans cooler is a must.
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That is about right for the power of my setup, the suspension is a work in progress so I will get dialed soon. And I am wanting to get a new converter, I know that is another thing that is probably holding me back significantly. I am slowly building this car up so Ill get a new one over the winter as well as the rear end.

Bad Sport said:
I went from a 7 1/4 2.76's to an 8 3/4 3.55 suregrip.

Let's just say the look on your face will be priceless, the first time you mash on it.
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Well I'm glad to here that! I am looking forward to putting in new gears the more I drive the thing. Wish I could see my own face when I do, I know I'll have the biggest grin on my face! LOL

I have found a set of 3.55s fairly close to me, and a set of 3.91s, I am going to try for the 3.91s but if not, I will have a set of 3.55s to run around in.
 
DartVadar said:
That is about right for the power of my setup, the suspension is a work in progress so I will get dialed soon. And I am wanting to get a new converter, I know that is another thing that is probably holding me back significantly. I am slowly building this car up so Ill get a new one over the winter as well as the rear end. Well I'm glad to here that! I am looking forward to putting in new gears the more I drive the thing. Wish I could see my own face when I do, I know I'll have the biggest grin on my face! LOL I have found a set of 3.55s fairly close to me, and a set of 3.91s, I am going to try for the 3.91s but if not, I will have a set of 3.55s to run around in.
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Once you try the 3.91 you will want more gear, 4.30 or 4.56 are a bigger smile, if you are not on the highway a lot.
 
Im never going back to 3.91s. Im a 3.55 man now. With the 3.91s my car sounded like it wanted to be a Mustang.You know:upshift,upshift,upshift,downshift,downshift,downshift; repeat.repeat.repeat. Oh sorry,you have an auto.
-Thing is; Ive run nearly every ratio from 2.76s to 5.13s. The 2.66low M/T liked the 3.91s the best.When I got the GearVendor and the 273 ratio A-833(3.09low), I liked the 3.55s best. I used to swap those chunks out sometimes twice a week.
-I even ran it as an auto for a while; both 2.47low and 2.74low. The 2.74 liked the 3.55s. On the street, theres something to be said for torque.Try not to get caught up in the hp numbers race. A well built 360 doesnt need a lot of gear. As always; just my 2cents.
-IMHO, a good street starter gear for an 360sbmM/T is between 10:1 and 11:1. So a 2.66 box needs 3.73s to 3.91s: and a 3.09box needs a 3.23 to 3.55. Thats it.
-And since the A/T has magical torque multiplication; It easily gets by with a bit less, say 10% less. So working it backwards;10.5/2.74 = 3.83. less 10% =3.45. Nearest sz is 3.55s. TaDa. I know; long story. Sorry. Hope this helps.
 
longarm said:
I'd lose that stock convertor immediately and go with a 2200 to 2600 stall for a decent all around street/strip package that can be driven daily without a bunch of headaches.A trans cooler is a must.
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Yes and with those gears it is going to make the convertor feel even tighter.

AJ/FormS said:
.When I got the GearVendor and the 273 ratio A-833(3.09low), I liked the 3.55s best.
.
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3.73's with my GVOD worked very well. You could do anything with the car with that setup. As in run 80mph down the interstate at 2900-3000.

I recently went to a 28" tire and 4:56's. Great around town and highway. a bit much for the interstate but I'm not on that very often. 2500 at about 60mph.
 
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