gear ratio question

[lkgaston]

i have 35" bfg tires with 3.50 gears, built c-6 trans. and a 427 w with 540 hp for the street. will this ratio work or do i need to change to 4.10? its a frame off restoration, so i havent driven it yet. just getting it back from paint.

 

[Broncobowsher]

Will it work, yes. Will it be good, no.
What convertor will you be running? That much HP generally needs a looser (higher stall) convertor then stock. If you have too tall of a gear for the tire and engine size you will really stress the convertor and make a ton of heat. and 3.50 gears on 35s will be a bit too tall. Loosen the convertor to match the engine and it will be even worse.

Now will 4.10 gears be the right choice? They will be better then 3.50s for sure. But depending on the engine you will probably need a bit more gear to really get it right. 4.30 would be my first guess (and a wild guess not knowing anything about the engine except the HP number). 4.56s are possibly a good choice as well.

 

[lkgaston]

2500 stall, the engine dyno at 540 hp and 560 tq. just dont want to burn up the trans. and not sure the stock axles will be strong enough.

 

[airbur]

2500....yikes!

 

[lkgaston]

yikes???? what does that mean.

 

[airbur]

Seems quite high for the 427's torque curve....but I don't know what your cam specs are among other things.

This is a good read....

http://www.hardtail.com/techtips/selectingconverter.html

 

[joshnjulie1]

Make sure you install the side wings for it so your take-off is flawless. 540 hp.....HOLY MOLY.

 

[NYLES]

http://www.grimmjeeper.com/gears.html

Punch all ya #'s in here

 

[Apogee]

Just for giggles, I caculated that the drivetrain combination specified with a 6000 RPM redline would have about a 170 MPH top speed...wow! Your HP/Torque numbers are impressive for a lifted, short-wheelbase, wheelie pulling machine. I've seen full-blown comp buggies get in trouble with less. I don't think you should be too worried about changing gear ratios with your current axles, but heavier duty axles with significantly lower gears (4.56) would be a good idea. The 9" can be built the live but the D30 or D44 won't be too happy if you ever use the skinny pedal in 4WD.

 

[rguest3]

Wow, 540 HP with a 2500 stall convertor for the street in an Early Bronco????

Curious to hear how street friendly that is.

Go with 4.56 gears.

 

[airbur]

Let see some pics! Did you go EFI? I see you're in Littleton...CO?....you might want to check out www.alpineclassicbroncos.com ....we're all local.

 

[bronc50]

Yup going to be dangerous
I run 5.13 gears on 38 inch rubber a nv3550 and a more less stock explorer efi 5.0 and it has no problem lifting the front tires 2 feet off the ground if I nail it in wile idling in first gear!
Your hp and torque you will be able to stand it on its back bumper...

 

[matts460]

Sounds like a fun truck to me! 4.57's will be great fun! Dont really need the stall unless your planning on some quartermile runs instead of trail running. A 2010 GT500 with 540hp has a hard time getting 170mph not quite areo enough.... so i really dougbt the Bronco could achevie that! LOL Im not sure i would want to be in it if it did!! I want your 427 windsor in my Aussie 1976 XB Falcon coupe! ALthough my Falcon's 460 has about 500ftlbs of torque i havent busted my 28 spine 9inch yet! And my 3.50 ratio third member came out of an early bronco! LOL So that could be hopefull.

 

[airbur]

I have 4.11s with my 427 and an 1800 stall. No idea what it drives like yet but will soon see.

 

[okorangebrnco]

From an opinion stand point- My plans for my Dad's Bronco are as radical and similar to a degree as yours. I am wanting to build a crazy motor for his with potentialy similar horsepower numbers. From working in a drivetrain shop, I am leaning towards 3.70-3.90's for my build. Only because I plan to drive this truck on the street in a "Hot Rod" type scenario. I am also after keeping the RPM's low enough to do 65-75mph down the highway. This gear choice will infact generate more heat, but I do not plan to wheel this truck like I wheel my Bronco.

All of this is based off of my opinion, but you have to decide what type of driving you plan to do. With a C6, there is only 1:1 final drive and screaming down the highway at 2500+ RPM's will infact tear a motor up prematurly.

 

[Broncobowsher]

The thing is with a 2500 stall convertor you really need to be turning a little more then that on the highway to keep from cooking the trans due to eternal convertor slip.

A small block has no issues turning 3000 RPM for days on end. These were sold new with little tires and 4.10 gears in the days of 70 MPH speed limits.

 

[lkgaston]

its a frame off restoration i have working on for a year. i had the frame and all parts under neath powder coated. the interior i put down lizard skin. the body shop has had the body 8 months and just got it painted. still have paint doors,hood, tailgate. voodoo blue. iam in Littleton ,NC. not sure how to down load pics yet. looking for someone to finish the painting.

 

[lkgaston]

just added some pics in the gallery.need to figure out how to put on the fourm.

 

[Doyle]

Looks like a good start on it. Sweet motor, bet she'll be a handful when punched.

 

[broncnaz]

Id say X2 on the 4.30 or lower gearing. while you will have lowend power that engine still needs to spin a little to be happy its not exactly a low RPM type of motor with those numbers. Plus the gearing will help the transmission live longer.