Re-gearing

[noahsdad86]

okay I checked and I do have a ford 9 inch rear end so yay for me thats better than the 8.8 right? I am going to hold off for now do to $$ but with all of this excellent information I will know exactly what to do when my wife forgets the checkbook at home.

 

[Broncobill78]

okay I checked and I do have a ford 9 inch rear end so yay for me thats better than the 8.8 right? I am going to hold off for now do to $$ but with all of this excellent information I will know exactly what to do when my wife forgets the checkbook at home.

Yup, that's a good thing. The Ford 9" is one of the best rearends out there. You'll find one under any circle-track race car you look at & most of the 1/4 mile guys run them as well. They aren't quite as dominant in the 4x4 world because a lot of guys run such large tires and stress the axleshafts so much that 1-ton axles & full floaters are frequently needed. Although, you can convert the 9" to a full floater if you want. The removable center carrier is what sets it apart. A guy can go to the track with 3 or 4 different center sections all setup with different gears & swap them out in the pits to fine-tune the car to the track. You can change a center section in 20min but if you're running a Chevy 12-bolt rearend you've got to swap the entire axle & those are a little bulkier when you're carrying a few spares. Jegs & other vendors actually sell heavy-duty plastic cases for the 9" carriers so you can bring a few extras. I've known guys to go 4-wheeling with a spare set of axleshafts & a center section. As a matter of fact one guy I knew who did that had an Early Bronco with a 9" *front* axle that he got from Currrie Enterprises. Really slick setup, he could repair anything short of a bent axletube in less than an hour right on the trail. A bent tube would just take him a little longer /emoticons/[email protected] 2x" width="20" height="20" />

But as great as the 9" is the 8.8" is no slouch either. You can run up to a 36" tire on that axle with no modifications and not have any problems. The 8.8" is a very tough & durable axle, a lot of good trucks are built with them.

 

[Justshootme84]

Noahsdad86, check your axle code or the tag on the rear axle. IF it's "H6" or "3L50 9 ...", you may be able to get by for a while with 35's until you can do the gear swap. IF you have 3.00 gears, you'll really notice the loss of power. And with the Ford 9" rear, you have the option of running a mini-spool vs a full spool or locker. You can find a mini-spool for the 9" for about $30-$40. It's what I had in my 84 Bronco, and the dude i sold the axle to is still running it with the full spooled front D44 TTB. I have a Currie 9" Nodular center chunk with 4.88:1 gears and a full spool in the 9" under my 78 Bronco, running 38" tires. It has enough grunt offroad for rocks, trails and mud pits. JSM84

 

[HallNBallz]

Hey fellas, i have an 88 302 bronco... does it have dana 44's front/back, 8.8 or 9?? also for 35" tires would the 4.10 ratio be good for mainly on road driving?? thanks i appreciate any help

 

[chrisdelaney]

what are the different size gears for the ford rear 9 in

 

[cchilders70]

I have 35" tires on my bronco and it is an 86. I have no problem having enough power to get threw any mud terrain thevlast week and it has been soaked here in Ohio. I have a 4" suspension and 3" body lift. I have been up to my door in this one bog many times and pulled out easilyish lol. This is a great discussion thou I might look intones gears thou.

 

[alan35]

I use for my problem this awesome gear ratio calculator

http://www.cargister.com/calculator-gear-ratio

 

[alan35]

is this link useful for anybody ?

 

[Caxtus]

Hi,

I am also thinking of re-gearing my 82 full size bronco. It has a 9 in 31 spline Ford rear end and I believe the front should be a Dana 44. From what I can understand looking at the tags on the diffs, the truck runs 3.00 axle ratio and have open diffs. I am attaching the diff tags for your reference. 

I am running 32 in tires and needless to say the truck feels sluggish. I am thinking about re-gearing and would like to ask you guys whether 3.50 or 3.73 is a better option both for street use and light off-roading. I am also thinking to swap the open diff with a limited slip in the rear. Is it necessary or very useful to swap the front with a limited slip as well?

Finally, since this is a fairly expensive upgrade what would be your suggestions in order to not completely break the bank? Based on my research Yukon is the king of this realm if you want quiet and reliable operation. Their low tier stuff gets branded as USA standard and sold for cheaper. I wonder if that is a good compromise. What are your experiences with the brands and what would be best budget oriented build?

Thank you for all the help.

 

[miesk5]

Yo Caxtus,

Welcome!

I can only guess at the tags, but others here can offer their opinion. So to figure out the ratios, as Seabronc advised:

Ring & Pinion Calculator by counting teeth Source: @ http://www.therangerstation.com/tech_library/Ring_Pinion_Calculator.shtml

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"Jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posi’s and lockers and 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading.

Put the transmission in neutral and jack up both tires. Turn one tire. If the other tire spins the opposite direction you have an open differential, and if it spins the same direction you have a posi or a locker." by http://www.differentials.com

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Gear Ratio Guide for Larger Tires @ https://web.archive.org/web/20100313072646/http://www.broncocity.com/resources.htm

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Compare to this one @ http://www.grimmjeeper.com/gears.html

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TRANSFER CASE GUIDE & IDENTIFICATION @ http://www.f150hub.com/drivetrain/new-process-id.html

Guess is that you have tbe New Process 208

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Ford typically builds 4WD trucks with a slightly faster/numerically lower front gear ratio than the rear so that off-road steering is enhanced. So a truck built with 3.55 rear gears will have 3.54 front; 3.08 rear - 3.07 front; 4.11 rear - 4.10 front, etc..." Following was in my MS WORD Notes and the source, Randy's Ring & Pinion has removed it from their current web site; "The gear ratio in the front of a four wheel drive has to be different from the front so the front wheels will pull more. There have been many different ratio combinations used in four-wheel drive vehicles, but not so that the front will pull more. Gear use different ratios for many different reasons. Some of those reasons are: strength, gear life, noise (or lack of it), geometric constraints, or simply because of the tooling they have available. I have seen Ford use a 3.50 ratio in the rear with a 3.54 in the front, or a 4.11 in the rear with a 4.09 in the front. As long as the front and rear ratios are within 1%, the vehicle works just fine on the road, and can even be as different as 2% for off-road use with no side effects. point difference in ratio is equal to 1%. To find the percentage difference in ratios it is necessary to divide, not subtract. In order to find the difference, divide one ratio by the other and look at the numbers to the right of the decimal point to see how far they vary from 1.00. For example: 3.54 · 3.50 = 1.01, or 1%, not 4% different. And likewise 4.11 · 4.09 = 1.005, or only a 1/2% difference. These differences are about the same as a 1/3" variation in front to rear tire height, which probably happens more often than we realize. A difference in the ratio will damage the transfer case. Any extreme difference in front and rear ratios or front and rear tire height will put undue force on the drive train. However, any difference will put strain on all parts of the drivetrain. The forces generated from the difference have to travel through the axle assemblies and the driveshafts to get to the transfer case. These excessive forces can just as easily break a front u-joint or rear spider gear as well as parts in the transfer case."

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http://broncograveyard.com

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Next time, please fill out your Signature with year, engine size, transmission type, transfer case type (manual or electric shift), locking hub type (automatic or manual) info & major mods such as a Lift, etc. for better responses.

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GL!

Al