GEARS GEARS GEARS, Please read before posting gear questions - Ford Bronco Forum
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post #1 of 330 (permalink) Old 03-04-2003, 02:52 PM Thread Starter
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GEARS!!, Please read before posting gear ?'s. Updated 11/11/03

Here are some really good equations for determining what gear ratio you may want to concider.
Remember that this is reference only and is based on equasitions from simple math.
Your tire size may be listed as 33/35/37, etc. but the actual measuremnet of the tire could differ once it is mounted on your rim.

Also this write is assuming you have an E4OD, or similar auto tranni.
These are figures that I came up with, to do your own just do:
Circumference of tire divided by the gear ratio you want.
Then compare you answer to the stock forward measurement of 25.5"s and then you will know if it fall over or under.

************************************************** **
Stock 29" tire (235/75R15), with 3.55 gears, 90.7" is circumference of tire, thus for every turn of the drive shaft, you go forward 25.5" or so.

33" tire, 3.55 gears = 103.7" circ, forward 29.2", about 15% more than stock
33" tire, 4.10 gears = forward 25.3" basically same as stock
33" tire, 4.56 gears = forward 22.7", about 11% less than stock

35"s with 4.10s = 26.8, 5% over stock roughly.
35" tire, 4.56 gears, 110.0" circ, forward 24.1", about 5% less

37" tire, 4.56 gears, 116.2" circ, forward 25.5", identical to stock (within error)
37" tire, 4.88 gears, forward 23.8", about 9% less than stock.

38.5" tire, 4.56 gears, 121.0" circ, forward 26.5", about 4% more than stock
38.5" tire, 4.88 gears, 121.0" circ, forward 24.8", about 3% less than stock.

FYI, for those who are thinking they can run a 35" tire with 3.55 gears...

35" tire, 3.55 gears, 110.0" circ, forward 31", about 22% more than stock. That means that your motor is working (and your clutch or torque converter) quite a bit harder to move your truck. That's why it dogs so bad.

If it falls "under" your motor does not have to work as hard to turn the tires, but it does it at a higher RPM. This means that as you go more "under" you lose top end. If it's "over" you'll have a higher top end, but less grunt.
************************************************** **********

Thank you.

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post #2 of 330 (permalink) Old 12-26-2003, 09:36 PM
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http://www.4lo.com/4LoCalc.htm This site give easy to use calculators for the info not listed above.

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post #3 of 330 (permalink) Old 01-21-2004, 10:52 AM
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Now some of us are poor little boys, and can only afford 31's. and I'm still using a C6, so would it be possible for the mad scientist to add 31's to the chart??

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post #4 of 330 (permalink) Old 01-21-2004, 01:54 PM
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how about 33's & 3.73's added to the list too please... :)

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post #5 of 330 (permalink) Old 01-21-2004, 07:59 PM
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gobucs posted a calc...try it out. and you have a c6, no overdrive, so your rpm is going to be even higher.

3.73 is pretty much between 3.55 and 4.10, so just estimate.
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post #6 of 330 (permalink) Old 01-21-2004, 09:53 PM
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Here is a gear calculator for you Tomb971 http://www.grimmjeeper.com/gears.html try this old to see what you want to run. Stock gears and 33 are not bad try 38's.

Last edited by 79F150; 09-24-2011 at 10:22 PM.
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post #7 of 330 (permalink) Old 03-16-2004, 08:51 PM
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Beerman
Here is a good ??? what about these trie size 40's and 44's ??
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post #8 of 330 (permalink) Old 03-16-2004, 10:03 PM
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I would say you need 5:13's for a set of 44's and a c6 tranny also with a np 203 or np 205 transfer case. That would put your RPM's at about 2690 @ 65 MPH.
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post #9 of 330 (permalink) Old 03-17-2004, 03:19 AM
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Quote:
Originally Posted by MudSlayer
Beerman
Here is a good ??? what about these trie size 40's and 44's ??
5.13s. you may be able to get by with 40s, a 351 and 4.88, but 5.13 is going to be better

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post #10 of 330 (permalink) Old 03-17-2004, 11:06 AM
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Thanks cus i wasn't just going to throw on 40's or 44's on a 4.11 gear i have 33's on it now, I was just woundering when i make the change!! Thanks
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post #11 of 330 (permalink) Old 05-19-2004, 07:17 PM
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Pffff.....while all you tools are doing this stuff with a paper and pencil I prefer to just use this..... http://www.csgnetwork.com/multirpmtirecalc.html


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post #12 of 330 (permalink) Old 05-19-2004, 08:07 PM Thread Starter
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Quote:
Originally Posted by 351Bronco
Pffff.....while all you tools are doing this stuff with a paper and pencil I prefer to just use this..... http://www.csgnetwork.com/multirpmtirecalc.html
Ya but do you honestly think most people here know there final tranni gear ratio?
I dont.

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post #13 of 330 (permalink) Old 05-19-2004, 10:40 PM
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Hmmm.....yeah, good point. But then again if theyre smart enough to do it with paper and pencil, then by god they should!


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post #14 of 330 (permalink) Old 05-19-2004, 11:20 PM
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Quote:
Originally Posted by Beerman
Ya but do you honestly think most people here know there final tranni gear ratio?
I dont.


Heheh. 1 to 1 Unless it's overdrive.

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post #15 of 330 (permalink) Old 07-17-2004, 12:29 AM
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still confused

Ok, im still confused. If i run my 35's with stock gears, its gonna give me less power and torque? and if i go to 4.1 its better??

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Soon to come: 35x12.5 Pro Comp M/T's, and a 6" susp lift.

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post #16 of 330 (permalink) Old 07-17-2004, 01:01 AM
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Gear swaps require a press, setup bearings if you do not have a high priced bearing puller, (clam shell type), a micrometer, a dial indicator, and a copy of the Yukon Gear installation manual. (Randy's R&P has it as a .pdf on their web site). Tolerances are measured in .000 inches. As well as a box full of hand tools and then shop air to torgue the pinion down.


As far as working the engine with 35's and stock gears....it's all about the power band. Your truck looks to do about all it can do before 2700 rpm. It's a truck motor anyways. Your truck engine willl have to increase power to turn the bigger tires. Being a '96, you'd be better off doing the around town driving with the OD off. Your really working the transmission more thean the engine with this setup. Although, a tired engine will also start to show problems as well. Oil pressure loss, overheating, etc.


It's not a BIG issue on the road. Heck, if 90% of your driving is pavement, you'll probably never have a serious problem. Off road obstacles are going to bite you though. Taller tires and stock gears will make the drivetrain work that much harder. You'll be overheating from the start.


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post #17 of 330 (permalink) Old 07-17-2004, 10:45 PM
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Quote:
Originally Posted by Beerman
Its common sense, and a little bit of math, maybe an 8th grade level.
Try reading it again, maybe you will understand better the second time.
Dude I read it again your right it is common sense, IF YOUR AT AN 8TH GRADE LEVEL.
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post #18 of 330 (permalink) Old 07-22-2004, 10:18 PM
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How to do gears!

Quote:
heycoach Ok so I now no that I want 4.10's but is this something I can do myself or is this a pro's job. Is there a tech write up somewhere I could not find one.
Same question? Anyone got a writeup? Or a good link to a writeup?

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post #19 of 330 (permalink) Old 07-30-2004, 12:44 AM Thread Starter
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If you have to ask, my opinion is dont try it.
By the time you bye all the tools to do the job (press, backlash tool, etc) you could have just drove the axle to some guy and had it done for a case of beer and $100.00

Most of the guys I know here locally will do gears for that price with a smile on their face.

"For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring."
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post #20 of 330 (permalink) Old 08-13-2004, 06:13 PM
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http://www.et-studios.com/motorsports/gears/gears.html

This is another really nice gear ratio calculator!!!

Dan

1995 f-150 5.0 special (x-road commision)
1986 ford bronco 5.0 efi (winter beater)
1985 mustang gt 5.0 5spd
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