How to find your differential gear ratio without stamps, tags, or tear down

[@The0Gamer379]

8 years later, you're still saving me (and certainly many more) loads of money buying the wrong stuff or having to rip it all apart.. Bless you.

[@briansmobile1]

Doesn't matter. The tire rotates the same number of times as your hub/axle/wheel etc. Your tires will have a greater circumference, but the ratio of revolutions will be exactly the same. ( I KNEW I should have said that in the vid, but forgot to- thanks for asking.) Please thumb up this comment so people will see it at the top!

[@ncrdisabled]

My dad showed me that trick way back in 1967 . Its amazing what the old master mechanics knew . It sad a lot of them do not want to share there info due to fear of being replaced. You are teaching someone else so you thoughts to be carried on.

[@Maerlyn1101]

THAT. WAS. ABSOLUTELY. AMAZING!!! Never, ever thought about it like that. I must say, coming from a gear head of old, I learn something new with every new video I watch. Thanks for all you do. Very helpful.

[@briansmobile1]

You're welcome- it makes my day that I could share this with such a grateful person as yourself!

[@briansmobile1]

Thanks man- I'm always learning. It's one of the things I really like about this line of work is the work that goes into one car is comprised of thousands of different ideas and people and it's always evolving. It's not boring.

[@robbiesharp311]

How do I find my gear ratio with the stamp on the door?

[@briansmobile1]

4.3 means that the driveshaft turns 4.3 times to make the truck wheel turn once. The more times it turns per wheel rotation the more torque and better off the line acceleration you get, but the lower speed per RPM.

[@michaeleisenbise4278]

I have a 1931 Ford Model A. There is only a number stamped on the engine as a VIN. And, you can only tell the date of engine manufacture. Noting about the differential. I needed this information. Used the method in video and it worked great. Thanks for a simple straightforward video. Thanks.

[@billmcmeekin7909]

Thank you. I was scratching my head until I followed your immobilize one wheel, and follow your formula. Stripping/rebuild of my 85 stepside and this resolved my quandary. Cheers from Canada ehhh :⁠-⁠)

[@briansmobile1]

You're most welcome Kelly- I'm glad you appreciate it enough to say so.

[@briansmobile1]

I actually take it in and have Kevin do it for me. Perhaps I can buy him lunch and have him let me film him doing it. The man is a genius! This one is going to need a complete carrier or axle due to lack of oil for thousands of miles.

[@hishamjallabi9767]

Awesome, now I can change my wrong reading speedometer gear. Thanks Brian, you are amazing.

[@briansmobile1]

solid rear axle means the axle housing is tubular and one solid tube/piece. Limited slip differential is a type of ring and pinion carrier configuation that can be put inside an axle whether solid or independent.

[@briansmobile1]

Welcome- I'm thrilled to be able to share it with you!

[@artmiller2066]

Thank you. Much similar to the other gentleman, I overheard the conversation on how to do that. I’d never actually seen it done. White board helped. I think you should repeat this one or make a masterpiece video that would go viral. I have a 4x4 and an old hot Rod. Great garage banter.

[@briansmobile1]

It does work on FWD vehicles- they have differentials too- they're just typically built into the transaxle assembly. You never divide by 2. You multiply by two if one wheel isn't rotating too in order to get the driveshaft to move because spider gears have a 2:1 ratio. You divide by ten because of the ten revolutions. You turn the wheel ten times because you want an accurate number.

[@briansmobile1]

This is going to be my ski truck for the 2012-2013 ski season. It just needs to be reliable by Dec and get a winch bumper and some side protection put on it.

[@davidclark3147]

Damn no wonder you got a good shop you got a good head on your shoulders dude

[@briansmobile1]

You're welcome- thanks for joining along.

[@roswalt1]

Planetary gears are still a magical happening in my mind. I know that they function but I still have a difficult time conceptionalizing that they function. Thanks for the information.

[@garysacramento6065]

Great lesson on gear ration. I have a 74 Bronco and want to change the rear end because when I'm on the freeway and left off the gas, the car almost wants to park itself when the slow down. I'm thinking it's a 4.10 contributing to my 10 MPG. I'll let you know.Thanks for the info.

[@briansmobile1]

yes. Anything with a differential has a ratio. Just don't multiply by 2 if it's got limited slip. etc.

[@andyc5612]

Well done mate. Easy to do on your own, and works for any car or truck. Really helpful vid.

[@derlymartinez9608]

I learn something every day. I’m ready to maybe rebuild the diff on my 08 super duty and I do t k own if it’s got a tag with the Info so thanks for this video, I know what to do now to get the ratio for my truck now.

[@SuperPetrolhead87]

Very helpfull video and information man,working in a main dealership you dont get to work things out such as gear ratios...it would all be on the computer which is boring and easy.cheers ive learnt loads from your videos!!

[@briansmobile1]

It doesn't matter what car you have. Differentials are either limited slip as I said or they aren't. Either way you can find a ratio. There's always going to be so many turns of the propeller shaft to so many turns of the rear wheels.

[@spelunkerd]

Great idea, Brian. I'm surprised it's not available from the VIN or other codes. I've wanted to watch how you do pinion crush washers, ie not just counting threads to reproduce what was there before. Hopefully when you do it Spanky will be there, to video exactly how it is done. I assume you use a press to get the preload right?

[@briansmobile1]

That's right. As I call them "spider gears" are rotating and that movement cuts the revolutions in half vs if both wheels were spinning.

[@YotaFan1]

I'm very serious. I can wait until the end of ski season. Especially if your going to be building an awesome front bumper for it. Please make video's and Don't forget I know the internet can be at best inconsistent but I love 3.4 T100's and would very much like to buy that truck when your finished next spring.

[@joejohn5398]

Correct me if I’m wrong here but I learned the hard way on my 95 ranger these 1/4 tons are designed with “dropouts” made for racing but utilizing in off road vehicles to quickly fix major repairs on the trail. I don’t know the specifics on front rear dropouts it’s based on how it drops but I found that out when I grenaded my axle and was left to repair in the boonies. Aka 3rd member.

[@4ampaul]

Very helpful video. I had an axle that I thought was 4.30, and when I counted 21.5 turns I didn't even have to math it out

[@Pali4life2]

I wasn't trying to criticize or insult you at all. It just made me laugh when you said that. I sincerely do enjoy watching all of your videos though.

[@funforall9741]

Thanks for the video I'm doing a custom transmission and this video saved my life

[@briansmobile1]

Thank you very much. That's the nicest thing anyone's said to me today! : )

[@BASGuru1986]

I have a pretty good understanding of differentials and have rebuilt a few but I am having a hard time wrapping my head around how one tire spinning cuts the rotations in half. Wouldn't the spider gears just slip around the stationary axle and still spin the ring gear the same amount?

[@eddielozada3694]

Thanks for a short, straight to the point, no BS video. 👍🏻👍🏻👍🏻🎄

[@musicsense104]

A Formula to remember for life. Nice explanation. Thank you.

[@fordwindsor351]

3.55 in my 98 Expedition with the 8.8 rear-end. I know there is a shit load of ford 9 in rear ends out there especially in the after market world but does ford still place them in certain vehicles still or did they completely do away with them in new vehicles.

[@TheTexasCoder]

Excellent video, thank you for that! So divide by 2 because there are 2 axles, or is that a generic formula for any rear end...10 wheel revolutions, count the yoke, multiply by 2 then divide by wheel revolution? In any case, thank you for the video, would this work for front wheel drive vehicles?

[@briansmobile1]

There will be means for locking it either electric or mechanical. If locked, you'll notice jerking and tire barking when you turn.

[@davidabcab]

I checked my Nissan D21 a while ago and also only lifted the one wheel, turned once and counted 4.8 to 4.9 revolutions on the drive shaft. Thought this was my diff ratio, but according to this, I should in fact double the counts I found on the drive shaft, that puts me at a 9.6, seems unrealistic to me. I will go back and do the 10x rev on the wheel and count again.

[@johnswimcat]

Thanks for making and posting this. I'll be using it tomorrow

[@500hardcore]

How do you determine the gear ratio on a used 99-06 Chevy front differential? With no RPO code? Thanks for the video.

[@briansmobile1]

You bet! Thanks for watching.

[@briansmobile1]

Check out the brains on Nicholas! Smart guy!

[@EchoRoastedNutz]

sorry if you already mentioned it but im just trying to make sure. Can this be used on any vehicle with any back end. I have a 1989 Jeep comanche 2wd 4l inline 6. can this method be used on my vehicle and also. when do you have to stop the driver side tire from moving or do you always have to?

[@hustla10188]

Great vid! Will this be the same for a fwd 1999 Audi a3 or Golf/jetta mk4?

[@briansmobile1]

You're welcome Roberto!

[@jewllake]

I love your videos they are so educational. I also like the way you are a teacher and explain to us on the white board, as i'm a junior high teacher myself.

[@DanielRamirez-os1bg]

yeah got mine rebuilt 4 years ago found out that t100's with 3.4 v6 4x4 A340F automatic is 4.30 ratio and manual trans are 4.10

[@TrueBlueEG8]

Can you pm me your details? Also tell me whether you would like pressed steel or acrylic plates, and what you want stamped on them. Or would you just like any random plate off a wreck? Any particular county you would prefer??

[@michoacanohh2227]

Same for a 2017 5.7 daytona i think it has the super track pak just want to confirm using this

[@roswalt1]

I am puzzled why you have to double the number. I would have thought that the drive shaft to axle turn ratio would be the same whether one wheel turns or both turn. I am guessing that it has to do with the planetary gears moving around inside there and the different types of planetary gears on conventional rear ends vs limited slip? Thanks

[@briansmobile1]

HELLS YES! I WOULD LOVE THEM! And no- it's easier to do a thorough job by hand.

[@benjaminescutia6153]

I need help on my 2006 GMC Canyon I need to know figured out if that one i planing to pit it in is the right one if it’s match with mine

[@DrewskisBrews]

BRILLIANT! You bag of tricks knows no bounds!

[@catch22678]

usually there is an option between the two. call ur dealer with the vin or lookup the codes in ur glovebox

[@briansmobile1]

Ratios are like honey badgers. They don't care. The important thing is if it's limited slip or not. Check to see if that other wheel to that axle is moving or not.

[@briansmobile1]

Yes. As long as you can count revolutions you're good.

[@Leckrovov]

lsd stands for limited slip differential solid rear axle is what kind of drive line you have in your vehicle.

[@TrueBlueEG8]

Could you do something similar by turning your engine and watching the drives turn to work out individual gear ratios in the gearbox? Good video. You still want those Irish plates man?

[@chadjohnson5137]

Just curious if you have any way to check front differential on a 2000 Toyota tundra

[@MarshieBoy]

Seems simple enough, thanks.

[@MadsWorld34]

i have never been able to test a none posi but now maybe i can. i have one i have to change soon and i know its a 3.55 so maybe i can check and see how it works. thanks

[@briansmobile1]

"It is a fool who looks for reason within the chambers of the human heart." People make decisions based on emotions. They study the facts- sure. However the end educated decision is based on the feeling at the time.

[@Mr69barracuda]

Never make a permanent decision based on a temporary emotion.

[@stigman24]

so it doesn't matter what vehicle you doing it on ? it will work the same way for every vehicle and the number to rotated is a fixed number 10 times ?

[@wreckerman13]

my 4x4 86 chevy blazer has a 1991 rear diff, and the original 1986 front diff. Will the ratios be differant? and if they are, how do I fix it so it's right.

[@miguelmaldonado9881]

U can also do 5 turns on the tire, it would of turned 10.75 at the yoke. Even 2 turns on the tire works too.

[@Hesam0000]

Bryan, on a 2005 Subaru Baja Turbo fulltime AWD with 4.4 gear ratio & 4-speed-auto can we change the ratio to get better mpg on the freeway?

[@annavariumful]

The white board was ok. Thanks for the vid.

[@juancervantes561]

I have a 78 F-150 and I would like to swap a used rear differential with disc brakes any idea which a wold fit

[@briansmobile1]

It doesn't matter. Circumference causes bigger tires to cover more ground per revolution, but your tires aren't on the ground for this. They are in the air and we're just counting revolutions.

[@SHADOWBLACKs650]

Wouldn't this be somewhere in the vehicle specifications ? Or a online search ?

[@kellyhansen6496]

Great tip! Thanks for sharing and keeping it simple.

[@clarktferrill]

I have 04 safari van...getting a clunk sound from differential feels like slack in drive train..any ideas as to what is going on?

[@Juciyblueberry]

hahah I love how he also teaches us about moving the decimal xD

[@melloyello89]

Yes the spider gears inside the differential have a 2:1 ratio on an open carrier.

[@KazDolla1]

Just saved me some time and money I can't wait until I get off work

[@mattroberts7199]

Does this method work for the front diff on a 4x4 also?

[@dannyd6288]

What does a 02 2500 burban come stock with in gear ratio

[@FamousByFamily]

what is the difference between LSD and solid rear axle.

[@mjb12141963]

You are a gift from God! Thank you so much!

[@wtedwards14]

Very informative and well spoken

[@jakegriep3965]

Does it work the same way with a front diff on a jeep grand cherokee? I bent my axle and I need to get a whole new front end and I need to know the gear ratio because its 4 wheel all time.

[@lowdertravis09]

Your front and back will b geared the same

[@htrn1967]

thanks for the knowledge, quick and easy.

[@6_30]

Thanks! I figured out my exact ratio's on my F & R.

[@briansmobile1]

Welcome Lonnie!

[@alexdesy6686]

But how do you find the gearing on the front axle?

[@lucasgreer5796]

thanks for making this vid I bought a truck and the tag was gone on the rear

[@YNTGUNS]

Also u jus got a new sub good video!

[@briansmobile1]

I'm not sure. I think they are still in Mustangs etc. but I don't follow the brand new stuff. I never buy new cars because of all the Dave Ramsey books my mom gave me/I read.

[@danmichaud5553]

Tags are only as good as new. How can someone know gear ratio has never been changed if your a second owner of a vehicle. Thanks for the easy trick. 🤙🏼

[@eastboundtrucking]

also wish you could have showed the rpo code along with the video! Thanks a million friend.

[@briansmobile1]

You're welcome.

[@jeffebner6701]

That was helpful and simple. Thanks

[@briansmobile1]

You're welcome!

[@dannyd6288]

OK cool thanks. I might do a video response to figure it out this way its looks more fun.

[@briansmobile1]

Thank you very much!

[@briansmobile1]

10 is one of the easiest numbers to do the math on- you just move the decimal to the left one spot. And yes- with more turns you're most likely to get it right that first time.

[@msharp9194]

Just do 2 rotations. There's no math then. LOL

[@briansmobile1]

Indeed!

[@nicholaspap7197]

How would u stop one wheel if u had a locking diff/posi

[@darrylm3627]

Good Stuff, Great Tips👍🏿😀