Can someone explain gear ratios and what they mean? - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 07-30-2014
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Icon5 Can someone explain gear ratios and what they mean?

im a little confused on what the difference is on gears. in the near future i'd like to put 33s on my 2.3l. i read in another thread that the gearing on a 2.3l is 3.45. i have no idea what that means. and i read in another thread that someone said 4.56 is the best gears for 33s on a 2.3l. so my question is why 4.56 gears? why not 4.88s or 5.56s? just some info would be awesome
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Old 07-30-2014
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there are charts that you can look at you input speed and tire size and then the gear is matched to a desired RPM so say you have 33's at 60mph and you want it to cruise at 2900rpm you input those figures and it will give you a range of gears. Now the choice you have to make is do you want good gas mileage or better acceleration its all a trade of and there is a range there you can pick from. I have 3.73 and with my tire size i could either step down to 3.55 for better mileage or up to 4.10 for better acceleration but each one has its own cost/benefits. And basically the ratio stands for how many times the yoke spins for every 1 revolution of the tires.
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Old 07-31-2014
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wow that helped a lot thanks. is it something i can't do in my garage? i don't really like other people working on my truck but if you need like a masters degree to do it i'd just pay someone
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Old 08-01-2014
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You don't need a Masters degree to change differential gears. I doubt many with a Masters degree could or want to do it.

You just need some knowledge on how to do it, some basic mechanics skills and some specialized measuring equipment. It can be done in a garage. However, if you don't understand gear ratios, odds are you don't have the knowledge or skills to replace them.

I set up my own race car differential gears but I still pay someone to change the gears in my truck.
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Old 08-01-2014
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Agreed its not all that difficult but you do need a few specialized tools and a lot of patience to get it right you have to assemble measure then add shims and measure and so on. For what you would spend on the tools and parts you could probably spend a few more dollars and pay someone to do it with far less headaches.
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Old 08-01-2014
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Originally Posted by pearlkid9988 View Post
Agreed its not all that difficult but you do need a few specialized tools and a lot of patience to get it right you have to assemble measure then add shims and measure and so on. For what you would spend on the tools and parts you could probably spend a few more dollars and pay someone to do it with far less headaches.
how much do you think it would cost to have someone put in 4.56 gears?
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Old 08-02-2014
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Depends on who you go to it varies greatly. You may find a mom and pop shop who has a tech with the tools to do it that will do it cheaply or you can go to a shop that specializes in rehearing but they may charge more to pay for those fancy tools they have id shop around but sometimes you can find some rear ends already swapped for sale and its pretty easy to swap a whole rearend in these trucks with basic tools and some jacks. But id price around I've seen them anywhere from $150- $400 depending on 2wd or 4wd and what brand of gears you go with. Also depends on rearend size IE 7.5 or 8.8. The 8.8 was offered in more vehicles so there is a bigger aftermarket for their parts. Id also suggest since your already going to have them in their for the gears getting a master rebuild kit and swapping all the seals may not be a bad idea either the kits are fairly cheap and it'll already be disassembled anyway.
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Old 08-03-2014
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Originally Posted by pearlkid9988 View Post
Depends on who you go to it varies greatly. You may find a mom and pop shop who has a tech with the tools to do it that will do it cheaply or you can go to a shop that specializes in rehearing but they may charge more to pay for those fancy tools they have id shop around but sometimes you can find some rear ends already swapped for sale and its pretty easy to swap a whole rearend in these trucks with basic tools and some jacks. But id price around I've seen them anywhere from $150- $400 depending on 2wd or 4wd and what brand of gears you go with. Also depends on rearend size IE 7.5 or 8.8. The 8.8 was offered in more vehicles so there is a bigger aftermarket for their parts. Id also suggest since your already going to have them in their for the gears getting a master rebuild kit and swapping all the seals may not be a bad idea either the kits are fairly cheap and it'll already be disassembled anyway.
yeah the other day i found an 8.8 regeared to 4.56 but i texted the guy and he sold it the day before :/ but i guess the 8.8 is a really good, strong axle. so i might just try to find one already geared and then have someone seal it for me and stuff
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Old 08-03-2014
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Looks like 4wheel parts locations are in abundance in California lol. I know someone that got their 4.88s done at one of their locations but it was down in Florida. They're fair priced from what I remember him telling me plus you could source the gears from them and have them install them as well, if that specific location does installs.
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Old 08-04-2014
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Yeah 8.8 is much stronger than 7.5 now granted i have and three with the 7.5 all were modified and high mileage and never had an issue with any of them. But for off roading the 8.8 is the setup of choice. But if you open it up for gears rebuild is a must because from my experience it may not leak now but once you start shimmying the axle shafts out it will leak. I cheaped out on a $5 rear main seal when i did my 5 speed swap and it started leaking almost immediately. So to me its worth the little seals lol don't want to have to yank it back out.
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  #11  
Old 08-05-2014
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Originally Posted by 99offroadrngr View Post
Looks like 4wheel parts locations are in abundance in California lol. I know someone that got their 4.88s done at one of their locations but it was down in Florida. They're fair priced from what I remember him telling me plus you could source the gears from them and have them install them as well, if that specific location does installs.
yeah going to 4 wheel parts is like my saturday thing so i'll definitely ask next time I'm there. i can't imagine it'd be cheap but it'd be done right at least
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Old 08-05-2014
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shouldn't be too bad since its just the rear diff. if it was F+R then yeah, it would be significantly more expensive lol
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  #13  
Old 08-06-2014
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Originally Posted by 99offroadrngr View Post
shouldn't be too bad since its just the rear diff. if it was F+R then yeah, it would be significantly more expensive lol
haha i wish i had a front diff
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  #14  
Old 08-17-2014
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Hey Bazman, figured I'd chime in, I just put 4.56's in my 7.5 about 9 months

ago. As far as specialty tools, a dial indicator for setting back lash, a depth

micrometer to set pinion depth, and a small shop press (12 ton is what I used) to

remove and install new bearings and a dial torque wrench for setting

preload. The guy helping me made a ingenius tool for setting pinion depth,

basically 2 pieces of aluminum flat bar that was bolted together to form a

"T", the bottom of the tee bolted to a carrier cap bolt and the top of the tee

bolts to the bottom side of the piece that bolted to the cap bolt. It had a hole

drilled in one end of the top for the depth micrometer to go through. The

piece that the micrometer sits on is even with the carrier journal center line which

unless someone was having a bad day at the foundry should be the axle

center line. You can swivel both pieces to get the micrometer located over

the pinion. Before you remove anything, check the back lash of the ring

gear, remove the carrier, then check the pinion depth. Now you can mic the

shim packs and get a reference for the pinion and carrier and adjust

accordingly. I remember there was a way you can stick a pry bar through

the carrier and a spin the pinion in one direction and it will spit the carrier

out. This thing is a tight fit so you'll have to fight to get it out otherwise. Definitely

use a helper if all possible and watch your fingers, lots of dangers in a rear

diff. ( crushing, pinching, cutting risks), just be careful and make sure you and

your helper know where and what each other is doing. Buy a couple extra

crush collar, just in case. Besides they're cheap and can ruin your day.

Now based on the original shim pack on the pinion, add or subtract shims.

Unlike the carrier shim, the pinion shims are direct reading, meaning that if

you subtract a .002" shim, the pinion will sit .002" lower. So to increase

pinion depth, you subtract and to decrease pinion depth, you add. Yes you

can reuse your old shims too. Until you get the pinion depth figured out, just

tighten the old pinion nut to take the slack out of the pinion bearings,

check the depth, adjust shims and repeat. Once you get the pinion depth

dead on ( well I think your allowed +/- .005") remove the pinion nut and

bearing and install the crush collar and pinion nut. Hold your pinion and start

tightening the pinion nut. You'll feel it getting tight, this is where you can

mess up the collar and have to start over. Take your time, keep tightening

until you feel the collar collapse, from here it goes really quick. Take your torque wrench and turn the

pinion, IIRC, you are shooting for 12 ft.lbs. From here, turn a 1/4 turn and

recheck until you get within 3 lbs., then go an 1/8 of a turn. If you got the

pinion depth within spec and you have the bearing preload (which is what

you just did with the collar and torque wrench), you just did the hardest part

of the swap. Next is the ring. Pull the ring gear bolts and save them and

with a brass or other soft face hammer, bump the gear off. Now put the new

gear in place and using half the old bolts spaced evenly around the carrier,

start tightening in a criss cross pattern and suck the ring gear up, now

discard the ring gear bolts and replace with new bolts and apply thread

locker. Torque in specified pattern. Now comes the fun, the pinion depth is

a set in stone measurement so to get the specified backlash ( the amount of

travel the ring gear is allowed to move when meshed with the pinion) you

have to shim the carrier left to right to make it fit tighter or looser in the

pinion teeth. Now unlike the pinion, carrier shims are not direct reading,

meaning that .002" shim on the right might equal .005" less backlash and vise

versa. The other problem I had was the shims had burrs around the edges

so a hone stone was used to de-burr. The carrier should fit snug enough in

the differential that you will be forced to use a mallet to bump it in. So

install, check backlash, remove and reshim, and repeat. Every manufacturer

has different backlash measurements so make sure to check and highlight

important measurements, pinion depth, pinion drag ( pinion bearing preload)

and backlash. I bought Motive Gears and the backlash was really tight,

between .006 and .008" but after 9 months of towing 2,500# (from day 1),

no whining or other problems, we also didn't bother with the marking

compound, just set it to spec. and let it eat but I might have got lucky so do

what your comfortable with. Just keep in mind it was a good days worth of

work. Also get the install kit that comes with shims and ring gear bolts.

I think the gears were around 179 and install kit was 59, but really comes

down to if you want to buy the extra tools dial indicator, depth micrometer,

press, torque wrench. But if you think you might do a buddy's gear swap and

charge a deal, you can offset the cost and end up with some new toys.


I was scared to death when I swapped gears but after it was said and done,

it really isn't that hard. Also don't forget the shop supplies,

brake cleaner
gear oil
RTV silicone
rags
thread locker
extra crush collars (at least 2)

I'm fixing to do this to my project Ranger when I install the Truetrac in my 7.5".

Hope this helps man, good luck.

Last edited by hustler54; 08-17-2014 at 12:17 PM.
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  #15  
Old 08-17-2014
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Oh, I forgot to mention tho I don't know if this is taboo or a no no, but I used the gear calculator at 4lo.com when I did my re gear. You punch in tire diameter, transmission gear ratio, target MPH and RPM and it will tell you what gear you should run. You can leave any variable out and it will calculate that. Pretty nifty calculator and accurate as well. It does have a transfer case ratio but if your like me and have a 2wd, just put 1 for 1:1.
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  #16  
Old 08-24-2014
Bazman2008Ranger's Avatar
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Quote:
Originally Posted by hustler54 View Post
Hey Bazman, figured I'd chime in, I just put 4.56's in my 7.5 about 9 months

ago. As far as specialty tools, a dial indicator for setting back lash, a depth

micrometer to set pinion depth, and a small shop press (12 ton is what I used) to

remove and install new bearings and a dial torque wrench for setting

preload. The guy helping me made a ingenius tool for setting pinion depth,

basically 2 pieces of aluminum flat bar that was bolted together to form a

"T", the bottom of the tee bolted to a carrier cap bolt and the top of the tee

bolts to the bottom side of the piece that bolted to the cap bolt. It had a hole

drilled in one end of the top for the depth micrometer to go through. The

piece that the micrometer sits on is even with the carrier journal center line which

unless someone was having a bad day at the foundry should be the axle

center line. You can swivel both pieces to get the micrometer located over

the pinion. Before you remove anything, check the back lash of the ring

gear, remove the carrier, then check the pinion depth. Now you can mic the

shim packs and get a reference for the pinion and carrier and adjust

accordingly. I remember there was a way you can stick a pry bar through

the carrier and a spin the pinion in one direction and it will spit the carrier

out. This thing is a tight fit so you'll have to fight to get it out otherwise. Definitely

use a helper if all possible and watch your fingers, lots of dangers in a rear

diff. ( crushing, pinching, cutting risks), just be careful and make sure you and

your helper know where and what each other is doing. Buy a couple extra

crush collar, just in case. Besides they're cheap and can ruin your day.

Now based on the original shim pack on the pinion, add or subtract shims.

Unlike the carrier shim, the pinion shims are direct reading, meaning that if

you subtract a .002" shim, the pinion will sit .002" lower. So to increase

pinion depth, you subtract and to decrease pinion depth, you add. Yes you

can reuse your old shims too. Until you get the pinion depth figured out, just

tighten the old pinion nut to take the slack out of the pinion bearings,

check the depth, adjust shims and repeat. Once you get the pinion depth

dead on ( well I think your allowed +/- .005") remove the pinion nut and

bearing and install the crush collar and pinion nut. Hold your pinion and start

tightening the pinion nut. You'll feel it getting tight, this is where you can

mess up the collar and have to start over. Take your time, keep tightening

until you feel the collar collapse, from here it goes really quick. Take your torque wrench and turn the

pinion, IIRC, you are shooting for 12 ft.lbs. From here, turn a 1/4 turn and

recheck until you get within 3 lbs., then go an 1/8 of a turn. If you got the

pinion depth within spec and you have the bearing preload (which is what

you just did with the collar and torque wrench), you just did the hardest part

of the swap. Next is the ring. Pull the ring gear bolts and save them and

with a brass or other soft face hammer, bump the gear off. Now put the new

gear in place and using half the old bolts spaced evenly around the carrier,

start tightening in a criss cross pattern and suck the ring gear up, now

discard the ring gear bolts and replace with new bolts and apply thread

locker. Torque in specified pattern. Now comes the fun, the pinion depth is

a set in stone measurement so to get the specified backlash ( the amount of

travel the ring gear is allowed to move when meshed with the pinion) you

have to shim the carrier left to right to make it fit tighter or looser in the

pinion teeth. Now unlike the pinion, carrier shims are not direct reading,

meaning that .002" shim on the right might equal .005" less backlash and vise

versa. The other problem I had was the shims had burrs around the edges

so a hone stone was used to de-burr. The carrier should fit snug enough in

the differential that you will be forced to use a mallet to bump it in. So

install, check backlash, remove and reshim, and repeat. Every manufacturer

has different backlash measurements so make sure to check and highlight

important measurements, pinion depth, pinion drag ( pinion bearing preload)

and backlash. I bought Motive Gears and the backlash was really tight,

between .006 and .008" but after 9 months of towing 2,500# (from day 1),

no whining or other problems, we also didn't bother with the marking

compound, just set it to spec. and let it eat but I might have got lucky so do

what your comfortable with. Just keep in mind it was a good days worth of

work. Also get the install kit that comes with shims and ring gear bolts.

I think the gears were around 179 and install kit was 59, but really comes

down to if you want to buy the extra tools dial indicator, depth micrometer,

press, torque wrench. But if you think you might do a buddy's gear swap and

charge a deal, you can offset the cost and end up with some new toys.


I was scared to death when I swapped gears but after it was said and done,

it really isn't that hard. Also don't forget the shop supplies,

brake cleaner
gear oil
RTV silicone
rags
thread locker
extra crush collars (at least 2)

I'm fixing to do this to my project Ranger when I install the Truetrac in my 7.5".

Hope this helps man, good luck.
wooooaaa. thanks man i saved this page cause i might not do this for a while I'm pretty broke. but thanks hopefully mine will turn out good too haha
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