4.10 or 4.56 gears for a 8-3/4 rearend

Posted By: mopar65

4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 01:52 AM

well my push rods are so posed to be here tomorrow. so that means i have to get off my butt and start building my 73 dart again. I have to take the 4.10 gears out and set them up right. so i was wondering if i should leave the 4.10 in it or go to the 4.56 gears. I have both sets of gears already so i wont be out any money. here is a little run down on my car.
1973 dodge dart weighs around 3400
11.1.1 440
Indy EZ heads flow 310-315 @ 600 lift
comp solid roller 264@ 0.50 and 634 lift
mopar m1 tunnel ram 2 750 carter carbs
727 with 10 inch turbo action 3800-4200 stall
M/T 275/60/15 drag radials.

I was thinking about using the 4.56 because i don't have enough converter right now.would the 4.56 make up the difference for the mismatched converter? look forward to your answers.thanks Mopar65

Posted By: MR_P_BODY

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:01 AM

Quote:

well my push rods are so posed to be here tomorrow. so that means i have to get off my butt and start building my 73 dart again. I have to take the 4.10 gears out and set them up right. so i was wondering if i should leave the 4.10 in it or go to the 4.56 gears. I have both sets of gears already so i wont be out any money. here is a little run down on my car.
1973 dodge dart weighs around 3400
11.1.1 440
Indy EZ heads flow 310-315 @ 600 lift
comp solid roller 264@ 0.50 and 634 lift
mopar m1 tunnel ram 2 750 carter carbs
727 with 10 inch turbo action 3800-4200 stall
M/T 275/60/15 drag radials.

I was thinking about using the 4.56 because i don't have enough converter right now.would the 4.56 make up the difference for the mismatched converter? look forward to your answers.thanks Mopar65

If its a race car 4.56 at least but you already
answered your question

Posted By: dennismopar73

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:10 AM

Posted By: mopar65

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:17 AM

wow that was easy

thanks for the help

Mopar65

ok that did not take very long on to the next question.with the 275/60/15 tires what would my trap rpms be with the 4.10 and the 4.56 gears?

Posted By: BradH

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:19 AM

1/8th or 1/4 mile? I run the same size tire w/ 4.10s and a converter that has about 7-8% slippage... it's spinning 6800+ through the traps at 125+ MPH in the 1/4.

Given the mid-range that a tunnel ram could have, you may not be as far off as you think w/ your current converter.

EDIT: Assuming 4.56s don't cause the engine to over-rev and actually lose MPH on the big end, they'd add another 400+ RPM on top of what 4.10s would turn.

Posted By: mopar65

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:34 AM

sorry about that. my home track will probably only let me run 1/8 to 1000 foot. but when i go to monster mopar or nor walk which are 1/4. i was wondering if the 4.56 would be to much gear for me. the 10 inch was for the other 440 i had in the dart that i never got to use and is going to have to do for now. Dewayne said to get a 5200 stall converter. which i plan to do but just not right now.i might just stay with the 4.10 but i wanted to see what you guys would say that are a lot smarter than me.thanks mopar65

Posted By: BradH

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:38 AM

Keep the 4.10s. I don't see your combination benefiting from any more gear given the short tires.

Posted By: dennismopar73

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 02:53 AM

456 is the gear
only one better would be 430 s
j m o

Posted By: Dart1031

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 03:05 AM

Quote:

wow that was easy thanks for the help Mopar65

ok that did not take very long on to the next question.with the 275/60/15 tires what would my trap rpms be with the 4.10 and the 4.56 gears?

My Valiant with a 440, 4.10's and a 275 radial traps at 6,100. I only shift it at 5,500 though. It doesn't go any quicker shifting higher, lol.

Posted By: smokinwoody

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/07/10 04:13 AM

the way I see it Bobby its only a 28" tire..if you were going to 31" or taller then I'd say go with the 4.56...forgot to say thats for 1/4 mile..

Posted By: 383man

383man - 06/07/10 04:15 AM

What I wonder is if it is tubbed or wheel wells stretched ?? If not you really cant fit a very tall tire under it. If so I would stick with the 4.10's. 4.10's with a 28" tire work good. You may not be able to fit any taller then a 28" tire under it. Ron

Posted By: 9 Sec Phill

Re: 383man - 06/07/10 04:24 AM

Sell them both and run 3.91 gear. The 440 has more then enough low end grunt (even with the tunnel ram) to move you down the track. If you go to low on the gear selection you will over power the tire. I have run 4.30 , 4.10 and then 3.91 and it went faster with lower ET with each change. This is with 28" tire A body. Why spin a motor higher then you have to to get the same results.

....Phill

Posted By: Cab_Burge

Re: 383man - 06/07/10 05:15 AM

4:10

Like Phil said them 440 don't need no stinking low gears, them be BB

Posted By: Ramcharger

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/08/10 05:27 PM

Another vote for 4.10.

Using Randy's Ring & Pinion RPM calculator (I'd say the slippage % is pretty low):

4.10 - 28" tire - 125mph = 6315 rpm
4.56 - 28" tire - 125mph = 7023 rpm

4.10 - 28" tire - 130mph = 6567 rpm
4.56 - 28" tire - 130mph = 7304 rpm

Your new engine probably has more RPM potential than I would feel confortable with using a semi-stock (internal pickup) oiling system. It will live a bunch longer if you keep the RPMs under 7000.

Just my

Posted By: Thumperdart

Re: 4.10 or 4.56 gears for a 8-3/4 rearend - 06/08/10 06:39 PM

I run 4.11`s in my dart w/a Hoosier QTP 29x13.5 steeet tire and love the way it runs at the track and more importantly how it drives on the street.....1.36 60`s at the track and I can drive it on the fwy for miles on end. Best of both worlds.