Should You Re-Gear Your Diesel for 37s?

Wondering if you need to re-gear your diesel for 37's? This video explains it all! I include examples of gearing calculators that help you figure out your new effective gear ratio after larger tires, and what gearing you need to return to your factory ratio. Whether you end up re-gearing or not, this video gives you the info the make the decision!
Here's the links to the gearing and tire size calculators:
Gearing Calculator: tiresize.com/gear-ratio-calcu...
Tire size/ speedo Calculator: www.tacomaworld.com/tirecalc
#diesel #regearing #37s

[@e30dean]

Great Info. Just got a 5.9 with a 47re and put 37s. I hadn’t even considered regearing because just like you, the truck seemed to do better.

[@payloadperformance9706]

Always enjoy your videos man, keep putting out the quality content! 💯

[@spencersgarage]

Thanks for the info man. Love your videos. I just bought a 2003 Ram 2500 5.9 Cummins with a nv5600 six speed manual a few months ago and loving it

[@JustDiesels]

Awesome choice!

[@ltanzie3363]

Another great video Austin! The timing of this video is also perfect for me. I just ordered a new 2020 RAM 3500 Megacab and the Carli 2.5 pin top suspension system and 37's from CJC Off Road! This has helped me with my decision to NOT re-gear.

[@k9trainerone]

You will find that you can not regear the new 2019-2020 3500 trucks yet as there are no after market gears available from Yukon or Nitro.

[@FxckTheAFT]

You may want to reconsider that depending on what the factory ratio is, if its anything like the 4th gens you'll have 3.42s & those are terrible with 37s, its fun being able to do 140mph down the highway, but even deleted only getting 13.5mpg highway & the 68rfe trans isn't liking it either, im gonna regear to 4.10s or 4.30s, keeping the 68rfe happy & being able to tow a good amount of weight again & better mpg in town & on the hwy

[@casperhoss2952]

Your videos are very helpful and informative. Thanks for sharing.

[@billthepilot1]

Great Video, you nailed it perfectly.

[@therandomweberlife5855]

As someone who has a heavily modified ‘13 Cummins that is regeared, I agree with what he says. I pull a camper a few times a year, and it’s rolling on 38s, I geared at 4.88 to try to save my trans, and regret the ratio choice. I wish I’d have done 4.10 or 4.30, no higher. I used to cruise at 65-70 @ 1200rpm, now I’m pretty much topped out at 60-65 unless I cruise over 2k rpm.

[@machinehead6892]

07 Dodge 2500 5.9d with 48re and stock 3.73, towing a 12,000 lb toy hauler in very mountainous areas with no issues, runs quiet on the highway and gets 21mgp all day long with a superchips programmer. Love it.

[@NA-sd1fo]

Well articulated. Thanks.

[@JustDiesels]

Here's the links to the gearing and tire size calculators: Gearing Calculator: tiresize.com/gear-ratio-calculator/ Tire size/ speedo Calculator: www.tacomaworld.com/tirecalc

[@smokinmetalcarfun2292]

Great job on the info good to know. When I go up on my tire size

[@OldNew45]

Great video, as usual. Very happy subscriber.

[@chalutric]

Great video. Now instead of explaining/arguing this to friends, ill just send them this video.

[@ismaelguillen7818]

This definitely helps.

[@cesar1981f]

Great video O6 ram 37 tires with 4.30 gears big diffrent pulling toy hauler but empty truck at 80mph doi 2180rpm . I will do 4.10 soon :)

[@mikestrucks]

As usual a great video 👍🏻

[@zacharyjames1848]

Liking the new intro Andrew!

[@JustDiesels]

Now you never need to hear me say, “what’s up this is Andrew” again! 😂

[@EddieLife3500]

Excellent video brotha

[@EVERYTHANGDIESEL]

Awesome vid brotha!! I agree with you on your points! Biggest factor to me whether to regear or not is what u want. In my case I wanted that low end power back like stock tires (go faster 🤣) the slight drop in egts is nice too. I ran my 37s on 3.73 gears too for long time and no issues like u. Keep the vids coming man!

[@JustDiesels]

Yeah if you care about going fast, re-gearing is definitely going to get you off the line faster with 37s!

[@EVERYTHANGDIESEL]

@@JustDiesels lmao facts

[@monsterram6617]

@@JustDiesels I care about going fast.

[@StVick]

Truck is beautiful, I got a 14' 3500 SRW on stock 17's with 12.50 35's. Got the 6.4 Hemi. Haven't regeared but I think in a gasser regearing may be preferable.

[@michaelliechty9906]

St. Vick . If i was getting a 6.4;with the 4.10 gear set on 35-37” tires is nearly perfect in my book

[@-o-The-Duke-o-]

Those Trailready BLs are gorgeous.

[@Ndw1995]

That calculator was extremely helpful. I was wondering if ordering a 5th gen with 3.73s or 4.10s from the factory would require a speedo recal if I went with 4.56s or 4.88s in the future with 40s. Turns out, if I order 3.73s from the factory, that speedo will be identical with 4.56s and 40s to an OEM setup and won't need to be recalculated

[@topless4runner]

Factory 4.10s make it a no-brainer.. I've been running 35s on my mostly stock '03 that came with 4.10 gears and the larger tires actually helped my cruising RPM at highway speeds.

[@dugefresh7063]

Love the video! I am thinking of buying a 2012 Used Ram 2500 Diesel (because for personal reasons that is the truck that works for me). I am thinkg of creating, over time, a nice over landing rig! I out of the gate am doing a Carli 3" Back Country Kit and new Rims and Tires, 37"s. I also will be inspecting the steering system and upgrading to Apex or Synergy Kit. Adding a Switch Pros Controller for electronics upgrades that are forth coming. Then a Leitner Designs Rack with F/R Bumpers etc. One of the first upgrades I was contemplating were front and rear lockers. That being the case the diffs would all ready be off the vehicle and was thinking of regearing at that time for the long haul due to the extra work the engine and trans would be doing and being booned way off road those situations that would require more throttle response from the jump; getting it back to factory made more sense, and I correct with this line of thinking knowing that now there are two new stops between 3.73 and 4.56 in the American Axle game then were available before. What are your thoughts???

[@JustDiesels]

If you go with a re-gear, basically shoot for the closest ratio to get you back to stock as that will help your trans shift correctly in an auto. It might not be spot on, but the closer the better! Sounds like you have an awesome plan laid out though!

[@Velf00]

Absolutely Agree. Ran 37s on 3:42 and very happy. 95% empty 5% towing travel trailer 10,000 lbs, just fine. Empty at 75mph 1600rpm. towing keep it in 5th

[@connorgoldstein4907]

I'm contemplating running 37's on my 4th gen. I do very little to no towing. How many miles are on your current transmission. I plan on putting a single delete tune in my truck and 37's but I am terrified of blowing the transmission.

[@ritzcake86]

For my 2012 lml with 37s, on a standard 55 mph highway or around town it will only go into 5th gear. And stay around 1500-1600 rpm. Then a 65 mph or interstate it will go in 6th and stay 1500-1700. Makes the drive feel smoother if you could say that.

[@erictharp6095]

Really Good video man..you're right about the diesel power...what if it was a hemi???I told My son 4.56s in his 05 1500 4x4 hemi with 35s..and he did...just waiting for weather to install

[@tylerp9620]

2006 Ram 2500 here and I agree 100% My truck is way more enjoyable to drive on 37s and stock gears. I tow a boat and Jeeps, tows great! Also do more vids of how you use the truck (bike trips etc.) It inspired me to keep and use my 3rd gen more.

[@JustDiesels]

I always mean to, but then I end up just enjoying the trip instead haha. Always happy to keep more of these trucks on the road!

[@colt._45]

Nailed it. I have 37's with 3.42. I don't tow much but when I do I just lock it up in 5th on the highway.

[@givnofuchs5742]

When you’re on the highway, what speed and what rpm are you at while in 5th?

[@bencallahan1425]

Great info thanks

[@PankajMohan]

Bruh, you make sense. 👍🏾

[@TinkerPrepper]

Great explanation! I drive a 5.3 but I sm a sub and like your videos 👍

[@Freakingstang]

Have an 07 power stroke ccsb with a Cummins 6.7 swap. Bigger turbo, injector and built 5R trans. Truck had 3.55’s. Cruising in the freeway 75-80 with 37’s I would get 17-18. When I went to 4.30’s it got the same mileage on the freeway and better mileage in town. The biggest difference was towing. With the larger turbo power and shifted up and towing 12-16k pounds and the 3.55’sthe truck would drink fuel. 5-8 mpg. With the 430’s it gets 12-14 towing the same weight.

[@dkcarroll13]

Nice vid man.

[@heavenisahalfpipe95]

Run 37’s on my stock gearing and I never have a problem. Pull a 25 foot travel trailer with barely any change.

[@jason328d6]

Other considerations are aftermarket turbos and what stall converter you run. My slightly bigger turbo is just a touch laggy, higher stall, looser converter helps that. I don’t think I need gears running 35s. Up with my mods I’m running 600/1200 at the rear wheel. Towing @8-10k it’s kinda hunts between 3/4 @70 and my EGTS cream up. Tow/haul us Aly fixes it for a little higher rpms and keeps the egts in check. Non towing it cruises @ 75-85 perfectly. Might consider gears at 37”, but my 35s are just right.

[@JohnDoe-du6yi]

My 97 12v has 37s with 4:10s and a nv4500 5 speed. It’s perfect for towing but if your not towing I actually think that 40s would help it out on the highway. My stock 4:10s were way to low when I had 33s on it. 70 mph was like 2600 rpm. With my 37s gps 70 mph is 21-2200 rpm. I don’t like really cruising it at speeds higher than 70 mph, and my mileage really starts to drop. I think 40s would put me at a nice 1800 rpm.

[@dethreveng]

Haven't watched the video yet, but I have a 6.0 Powerstroke on 37's with 3.73 gears. The power difference is insane, once I get the money up I'll be regearing to either 4.10 or 4.30. 35's I didn't worry about it, but the 37's really lug along.

[@kylemoore9626]

They need more RPMs than Cummins to make torque

[@TATEXPRESSINC]

I love the video

[@jaycourant5394]

Great video, thank you! What has been your experience with friends driving the 3.73 (68RFE) on 40"'s?

[@chrisb.5295]

I run 35x12.50x17's on my 02 with 4.10 gears. I have absolutely no problems with it at all.

[@mannyg85]

I have 35s on 3.42 gears on my ‘17 ram 2500. I don’t haul much it’s my daily driver. I’m using it as a welding rig now, I may have around 2k of weight in the bed. I want to upgrade to 37s I’m on the fence about regearing. The truck is leveled on a Thuren fab kit also.

[@mcwendel8066]

I had a 6sp JKU with 37s and it had stock 3:73 and it was fine. That being said i did rehear you 4:88 and it was better. But with a 2500 diesel i definitely don’t think ya need to with 37s. If you’re towing or wheeling you’d definitely be better off though

[@realistic.optimist]

As a Licensed Mechanical Engineer stay within 10-15% of the original tire circumference with the stock rear gears are you are fine. I ordered my F-350 with 3.55:1 knowing I was going to 38's. No issue. This issue exists just to be an issue.

[@jeffreyyeater1780]

Im with you . 35 s on my 06 cummins . I like it fine . Ive driven trucks that are gear bound . its horrible .

[@ricklp1861]

I also run 37's on my 5.9 ! Runs great on stock gears

[@reaperreaper5098]

Yeah, but there are and were always multiple options for the stock gears. 4.10s are a stock option, and those will handle things like 37s and tall lifts far better than 3.42s, which were also a stock option.

[@fedeleon1172]

I have an old 6.5 turbo diesel detroit tahoe 4x4 on 33s with the original 3.73 gear, but under 2k rpm in lacks a little power, I was thinking into going up to a 4.56 o maybe 4.88 but I am afraid of make rpm higher and higher

[@Ulfstigandr]

My rig would be ideal with 4.30s. With 4.10s i think your advice is quite apt. Just slap on the 37s and try it out. Though if i tear open my axles and add lockers wouldnt it be worth it to just add the gears too?

[@tylermiller8580]

Also gotta talk about steering and power steering and less braking with bigger tires.i got 2006 dodge 2500 6 speed on 37s with 4.10 gears truck had 33s when I got it would rev out at like 90 went to 37s now I can actually drive without being revvved out

[@supporterofsanity]

Great video and topic! The most common reason I see or hear rather, to re-gear newer Rams is due to supposed transmission issues. I have run 35s for three years on my deleted and tuned 2017. No issues yet. Does anyone have any actual proof/ data this will prolong transmission life with larger than stock tires? I plan on 37s on my next set.

[@JustDiesels]

From what I see the issue comes from the guys that are running 37s with deletes and tunes, and then blame the tires for the blown trans. I've got friends with over 100k trouble free miles with 3.42 gears, 68RFEs and 37s. Drive nice and the trans will last!

[@michaelengelhardt5296]

I have an 04 with a level kit on it. What all do I have to do to put 37s on it

[@manicmotox4214]

Just a thought I want to put out there. From a mechanical perspective, I understand with a Cummins why there would be no need to re-gear. However, with a 7.3L Powerstroke....I would think you would want to, as the 7.3L doesnt have the same torque curve the the inline cummins has, since it is a V8. So would it make sense to re-gear a 7.3 with 37's?

[@ericl5973]

My manual G56 with 3.73 revs too high on Texas 80mph highways. Using a set of 37s instead of re-gearing to 3.42. Time will tell if I gets better highway fuel economy by keeping the engine below 2000RPM.

[@coryferrill3405]

I have a 2015 dodge 2500 megacab hemi am I still good to run 37s?

[@TheFarmersLife]

I put 35x12.50x17 on my 2012 3500 Mega SRW a few years ago. 3.73 gears. Noticed no difference in the way it performs at all. Probably give 37s a shot when these tires are done. I believe Nitro gear makes a 4.30 gearset for these trucks I've seen people talk about on the forums. Definitely would run just the tires for a while first before I regear. Also am running a CPS 100hp tune and trans tune all the time. Drives great.

[@JustDiesels]

With a tune and 3.73s you might be happy on your existing gears! The truck will definitely be slower off the line on 37s though.

[@omen2098]

I'll agree you can get away with not rehearing.... However in my case my mini excavator is 12,500lbs operating weight and my gooseneck is 8500lbs.. I was on 35s and stock gearing and I could definitely feel a power difference needless to say I went back to stock size I do like the look of the bigger tires but when you tow heavy frequently let's be honest they don't belong on there

[@surfstarcc1]

Running 37s on my 99 Cummins, 5spd, 3.55 gear, tows boats of all sizes to shows. The only negative I found is my egts are a bit higher at Cruise speed and my mileage dropped significantly.

[@graydensgarage]

I had 35s on a jeep tj it was just fine, I've had 37s on my 1500 chevy, now on my 14 cummins I won't regear unless I do over 40

[@thejuiceisloose8703]

All these shade tree mechanics forget that these newer trucks are all making 700 to 1,000lbft of torque. 37s on stock gears ain't hurting anything. Especially the trucks that are running 8 and ten speed transmissions.

[@Nick0777]

If I want to order new ram 2500 and later put 37”, should I order 3.73 or 4.10?

[@stentonwhitmore5598]

I re geared to 4.56 on 40s, I have better power, less stress on the trans and it’s not hunting for gears, I have the 6.7 it came with 3.73. You would really benefit for regearing your truck.

[@realistic.optimist]

As a licensed Mechanical Engineer as long as you stay within 10% on the RPM of where you were you are fine. This is an issue for the sake of being an issue. IF you go to 40's or bigger from stock yea you probably need to re-gear. 37's or 38's this is a moot issue. I specifically ordered my truck with a lower gear knowing I was going to 38's.

[@lac1260]

I’ve been running 37s with 3.73s and really like it but my 68RFE just went out. Every transmission shop says regear to at least 4.10s. Some won’t warranty their built transmissions without proof of regear FYI.

[@samdog1232000]

What year is your truck and how many miles? I’m on the fence to re-gear.

[@Bananahammock88]

When I bought my Cummins, towing my 40 foot fifth wheel was a breeze. After leveling it with 35’s, it almost struggles

[@freak4nascar2]

What about if your going to add a 2nd gen swap ?

[@terryjensen72]

Last June I purchased an 07 ram 3500 dually with a six speed manual and 5.9 Cummins and stock 235 tires and it is twisting 2k at 65 mph. Driving me nuts. Not sure what gears I have but i know I need to get taller tires Bad. But I don’t want to spend a lot of money. Definitely need at least 35 tall but width is the problem.

[@jtdirte]

2016 2500 with the 6.7 on 37" tires, was considering adding lockers to the truck. Stay with the factory 3.73 or go to a 4.10?

[@andrewmalcolm5904]

Hey man, I’d really recommend reverting to the stock diff covers. The engineers at Dana/American axle spend a ton of time on oil flow and those aftermarket covers totally change the characteristics of the flow. Gale Banks has a great video series on it.

[@cencoast_7.340]

I personally know a ton of people that have been running Mag hitec/flat back covers for decades and they have had Zero issues. Yes, you are right, they may not be as efficient as stock or Banks outrageously priced cover but he's going to be ok.

[@andrewmalcolm5904]

SoCali7three yes I’m sure he’ll be okay, I guess my point is there is no benefit to those covers other than aesthetics. Lots of work is done on the geometry of the stock covers to make the flow as efficient and effective as possible. The stock cover makes sure oil gets to pinion bearing at all angles and temperatures for example. These tests are not done by aftermarket companies.

[@andrewmalcolm5904]

And I agree banks cover is ridiculous. It is solving a problem that doesn’t exist like the other aftermarket options

[@dutchthurman3169]

The new Banks diff covers are the best covers if you tow or go more than 30k before fluid changes...

[@JustDiesels]

This cover went on before the Banks were even a thing! I’ll agree that the Banks is superior, but there’s lots of people running million mile hot shot trucks with flat diff covers so I’m not losing sleep over mine! It isn’t worth pulling this one off, but I’ll do a Banks on the next truck.

[@chadwalmsley2769]

I'm running 456 gears and 36.x15.50x20 at 70mph I'm running 2000 rpm.im off road alot and the 456 gear in 4 wheel high is amazing never need 4 low for anything.

[@efrenaguilera7744]

Shoulda posted this a while back lol. I have an 06 with the 48re on 37’s. When I first Re geared it, I went with 4.56 gears (biggest mistake) then went to 4.10 gears which is a lot better but I do a lot of driving from Colorado back to California, I average about 70mph at about 2k-2200 rpm on the hwy. I wish I woulda just stayed stock at 3.73

[@JustDiesels]

Yeah I had a friend that did exactly what you did! Spent all the money to go to 4.56 because that’s what he read he should do online, and then spent all the money to go back to 3.73s haha. If this video helps one person pick the right gears than it was worth it!

[@lapincfl]

I have the 48re on my 2006 Cummins and I've been running 37s for the past year on my 3:73 gears. I also monitor my EGTs and have always been told to always keep them under 1350 degrees. Well when I'm towing a mere 4k pounds and I'm trying to cruise at 65-70 my EGTs rise up to the high 12s. It's like I can't find a sweet spot to cruise on the highway with towing without rasing my EGTs. Not to mention, no matter what I'm towing, even when I'm not towing anything it feels like my truck is struggling to make it off the line after a complete stop. It literally feels like a really need a re gear. Now just yesterday a tranny with a 6k performance build less than 2 years old just went out. Not sure if this has anything to do with the gearing being so off but now I'm staring down the barrel of another 5 or 6k tranny build. Almost makes me want to buy another truck and quick dumping my entire life into this one.

[@JustDiesels]

I have to say my truck has none of those issues! EGTs are completely normal, and I’m still on the stock trans!

[@leonislas9744]

What about a 3/4 ton truck because I just bought 2020 Silverado with the 6.6 gas and I have had my 37s for about a month now, I just wanna hear your opinion because you definitely have more experience than me

[@bryancollins942]

Aren’t port axles another way to raise the axle higher off the ground?

[@davidperra4104]

I am not able to see the link to the calculator. Could u send it to me please?

[@jp2073]

I want to buy a 2nd gen. What gears are on your '99? How does it drive/haul with 35" tires? Are u going to re-gear? Love your trucks. Thank you

[@randyboynton]

How wide are the rims? Really like the look of them.

[@JustDiesels]

These are 20x9.5 Trail Ready wheels. Here's a link if you're curious: www.cjcoffroad.com/Trail-Ready-BL20-20-x-9-Simulated-BeadLOOK-Wheel-p/bl20.htm

[@Therealfrenchiedad]

2018 power wagon... I know it's not diesel. It came with 33x11.50 and looks like a roller skate. I put 35x12.50 on the stock 17's and can't tell a real difference with the stock 4.10's and 6 speed auto, however I do get pulled over often as I'm about 9% off with the speedometer... No I'm not changing it until I go to 37's. My truck is on my channel if you care to see the set up.

[@bruta1f3ar]

I was on the fence about re-gearing but this video helped me decide to keep 3.73 for highway fuel efficiency. I was recommended an Eaton tru-track locker upgrade in the rear when I flush diff fluid. Any opinions on that vs an air or electric locker?

[@JustDiesels]

If you have on board air for other things then you may as well, but I think the e-lockers are a little more reliable since there’s less stuff involved.

[@mikemotor-tom5474]

I have a 2003 3500 with ARB air lockers front and rear 410 gear ratio with 35s, it works well. I never had issues with the air system. I love being able to creep up steep terrain while my friends have to get a running start. Less wear and tear on my truck.

[@xc_4x4]

I have a Hemi Megacab. Should I regear since it’s not a diesel? I have the same stock gears

[@ianh3007]

What size is the lift in the silver cummins with 37s? Looks awesome. Great video

[@JustDiesels]

3” with 37s!

[@ianh3007]

@@JustDiesels nice man. It looks really clean.

[@KR15nAK]

I have an 03 2500 cummins I put 35s on with the stock gear ratio and have had 2 48REs loose the drive gears. I do pull and plow with it. I'm convinced I was putting too much work on the transmission. Can anyone either confirm or deny my theory?

[@JaronAames]

Interested to hear what PSI you run your 37s I have a 3rd gen Power Wagon with 37s and the stock 4.56 gears, so far after a few thousand miles I’m very pleased with the results.

[@555pa555]

Hey I have 05 power wagon and wanting to put on 37s do u feel a differents with the 37? And mileage

[@JaronAames]

@@555pa555 I definitely can feel that the tires are much heavier. The truck felt peppy with 35s. I wouldn’t trade the offroad improvement or or the look that the 37s give the truck. I’ll average 12 on the highway. So not too bad.

[@artiedelimitros9443]

Did your MPGs change with the stock gearing going to 37s both around town and on the highway?

[@JustDiesels]

definitely! There’s no way to fight the physics of larger, heavier tires with more rolling resistance from aggressive tread patterns. The truck still gets solid mileage though in the high teens and even low 20s if I baby it.

[@purebloodedpatriot9352]

What does the AEV programming module good for?

[@JustDiesels]

It allows you to calibrate your speedo, change TPMS and a few other things on 14+ Ram trucks.

[@andybd11a]

My truck has 37s carli pintop 68rfe 2017 with 342s. I'm re gearing cause the 68 has some issues. I will go to 456s. If I find them a bit low I will step up to a 38.

[@mikemosley1396]

Id check out 4.30s. Just got them and love them. I think 4.56s would be too low even for towing if you ever hit the freeway. I have the same set up at you btw.

[@monsterram6617]

I've run 4.11s with 37s for about 5 years. I hit 2000 RPM in 6th @ 85 mph. Regular cruising is 1600 RPM @ 60 mph.

[@portalbucket5365]

Ive got 4.10s in my 2nd gen so 37s would help me out

[@elliotheichel8480]

He never mentioned mileage, not that people drive diesels thinking they'll get great mileage, but I always averaged 18ish mpg with stock tires 285s, 16 with 35s, and 14mpg with 37s. So yes our trucks can do it no problem 👌 but it will make them work a little harder often. Thats on a 2017 ram 2500 with a carli commuter 2.5

[@DocHolliday3841]

What about 40" tires? Know anyone who has run 40s on these trucks with factory gears?

[@JustDiesels]

With 40s you want to re-gear. You could probably get away with it on a 4.10 truck but that’s pushing it! Haha

[@troutriver58]

Would your general conclusions hold true for the 442 ftlb Jeep eco diesel with 37’s?

[@JustDiesels]

My tip is always to put on 37s and then see how you feel. No sense in re-gearing until you know you need to! The Jeeps are a little more likely to re-gear though since they have smaller drivelines and less power than the HD trucks.

[@woolfair]

I'm running 38s on an eco Jeep Gladiator. I have zero desire to regear.

[@Truckfarm]

What about your speedometer

[@555pa555]

What offset u running on ur rims I have a 05 power wagon with 456 gears and want to run 37s

[@JustDiesels]

These are 5.5” backspace and 9.5” wide so about +7 offset.

[@cencoast_7.340]

My 97 CCLB4x4 7.3 has the stock trans and 4:10 gears. If anything I would gear down for the same reason. Barely hitting 60mph and I'm already spinning 2k+, annoying when trying to go 70-80 and the engines buzzing like crazy!

[@JustDiesels]

That’s exactly why I was so excited to get 35s under the OBS! I can finally keep up with traffic now.

[@cencoast_7.340]

Just Diesels I’m considering going 37’s just so I don’t have to re-gear lol. Great video man. Stoked to see guys from 805 on here...I’m from SLO myself.

[@dcruz97]

37s on 4.30 gears amazing I’ve gone thru 2 transmissions on 3.73 due to not regear and I haul a lot

[@jamlocal40bm85]

what does it take to clear 37s on a 2nd gen?

[@JustDiesels]

Lots of fender cutting since the front wheel wells are pretty small.

[@afonsogarcia9997]

can someone explain what appears to be the different measurement standards please? Stock: 265, New: 37 / Stock: 70, New 12.5 ...

[@kylescaggs]

265 is metric tire sizing. For instance a 265/70/17 is 265mm wide, the 70 is the sidewall size as a percentage of the width. So a 70 is 70% of the 265 width, the 17 is a 17 inch wheel. The 37x12.50x17 is a flotation tire size 37 is height in inches, 12.50 is width in inches, and 17 is wheel diameter in inches.

[@kustomaf7606]

kylescaggs you’re right. The formula with that tire size as an example is 2x265x70/2540+17=31.6” So, 2(constant) times width in mm, times second number(ratio), divided by 2540(constant) plus rim diameter = tire diameter. I’m no mathmagician but I’ve used that formula forever to figure out wheel/tire combos. Of course there’s websites you can plug those numbers into. Thought I’d share

[@calevel]

My largest tire I could have on my same truck as yours was 33”. What do you have to be able to go up to 37”?

[@JustDiesels]

You need a 3” lift, high clearance control arms, and wheels that are 8.5-9” wide with +18 to +25 offset. With a little trimming they fit great!

[@calevel]

Just Diesels you probably meant to say from -18 to -25 ( negative) offset in order to better clear. I’m currently running 20x9 with -12 I should probably be rubbing a bit don’t you think 🤔

[@topless4runner]

Depends whether you're willing to put up with a little tire rub on your control arms. Factory wheels can fit 35s with only a little rub on the UCA near full steering lock, and thats with no lift, 100% stock suspension. 37s kinda fit too, but rub more. I've been running 35s on my otherwise stock '03 for years with zero issues (minor rubbing), including off road.

[@montanaairframer]

On a diesel, save the money spent on re-gearing to add power to the engine. Intake, exhaust, deletes, and tuning will increase power at all RPMs and can move torque to lower RPMs for towing.

[@jessegranados909]

I got a Ram 3500 with 3:42 gears and the Aisin trans. Want to put 37” tires but I’m confused about gearing. Calculator says I would need 3:78 gears which is not to far off from stock. But when I check a gearing chart it says I need at least 4:10. Which is correct? Anybody.

[@JustDiesels]

Since I’m guessing you got a 3500 to tow, I’d put 4.10s in that truck. Should be perfect with 37s on that trans. If you’re doing mostly unloaded highway, stay factory or do 3.73. Hope that helps!

[@jessegranados909]

Just Diesels I only tow about 3 times a year, under 10k total. Rest of the time it’s my daily driver mostly city.

[@JustDiesels]

I’d say try it on the factory gears then and see how you feel. That will give you a good gauge of gearing, but I have a feeling you’ll end up with 3.73s.

[@jessegranados909]

Just Diesels Thanks. Great job on the videos to. Keep them coming.

[@Steadierpark]

Someone mentioned lower egt’s…do you think that will effect the regen efficiency/reliability on the 5th gen emissions system?

[@JustDiesels]

With 37s you actually raise EGTs and engine load slightly, which is the absolute best thing you can do for reliability of the emissions system. Higher cruising egts means better passive re-gens and less load on the system. That’s why you see people with grocery getters having dpf issues and the hot shot truckers with constant loads getting better lifespan out of the system. It’s designed to operate best with some heat and longer highway driving!

[@Steadierpark]

@@JustDiesels that makes perfect sense! Even more reason to do this because right now it’s a daily and for off-road transporting dirtbikes.

[@Steadierpark]

And thank you for putting this out. Now when the haters tell me I need to regear from 3.73 I can set them straight. I actually used the gearing calculator and if nitto ridge grapplers are actually 36.5” then my gears end up at 3.42. I can rest easy now with my plans because my goal is keeping this truck forever!

[@JustDiesels]

Yeah 3.42 is still a very usable ratio. In fact, that’s the ratio all the 14-18 trucks had from the factory!

[@rt86000]

Would regearing improve my mileage?

[@JustDiesels]

It depends on your driving and factory gears. Around town and starting from stops frequently, re-gearing will help MPG. If you’re just highway cruising though it may hurt. Ultimately the name of the game for MPG is keeping the engine in its peak power band as much as possible, so go with whatever accomplishes that!