Regearing and doing 37s right

[MrCooper]

OP, what kind of off-roading do you plan on doing? Knowing this we can more easily guide you in requirements and stages.

However, I think I would search out a used 2-door Badlands and consider trading yours in. By the time you pay for the gear and axle upgrades you may be more than the price delta on a trade-in. And everything would be warrantied, if that is a concern. The manual BL has 4.7 gearing which is a good combo for 37's, especially on a 2-door. And if you are just mild off-roading then I wouldn't even worry about upgrading the steering rack.

Honestly, I'm just getting into this so it would be mild but I am also looking to quickly learn and push the limits as I connect with others, more experienced.

I did consider possibly trading for a BL. But I thought if I "needed" to upgrade to 5:13 gearing anyway, then it wouldn't make much sense.

Warranty is not a big concern but I do currently have a 7 yr ext warranty which should cover these parts as well.

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[indio22]

Equation for RPM:
(mph x final drive ratio x 336) / tire diameter = RPM

My stock manual trans base RPM in highest gear at 70 mph:
70 x (0.646 x 1 x 4.46) x 336 / 30 = 2,259 RPM

Same as above but with 5.13 diff and 35" tires at 70 mph:
70 x (0.646 x 1 x 5.13) x 336 / 35 = 2,227 RPM

At least for the base manual Bronco, if switching from 30" to 35" tires, to keep around the same top gear RPM, seems like you'd want to go with 5.13 diff gear.

OP you can try same to compare your stock Bronco version when adding 37s, maybe you come out with a different diff gear target. I know the base Broncos were geared a bit short (higher rpms).

 

[Dusty]

I'll push back slightly on @RagnarKon's statement that 5.38 would be better for off-road and 4.88 better for on-road. In my opinion 5.13 is perfect for both, coupled with 37's, 2.3L and the 7-speed. I've been running 5.13's in mine for a while now and I haven't lacked for lower gearing off-road, and on-road it's just right, with 6th gear still usable.

I would agree with the others on the proper upgrade path. Do the gears last. I ran the 37's for a couple of weeks before I swapped in the re-geared axles, and it wasn't un-drivable with the 4.46's. But it wasn't ideal. I think it's good to get that perspective before swapping the gears, just so you know by your own seat of the pants, what you got for the money.

If your Bronco already has the rear locker, your M220 shouldn't have the welded ring gear. You should be able to simply re-gear without needing to buy any extra parts other than an install kit.

 

[RagnarKon]

A little on the side discussion, but if I had 4.7 and wanted to go to 5.38, I'd only regear the rear axle? I don't know why, but I thought the gearings had to match. Starting to wonder what I'm missing.

If you want to drive in 4WD they have to match. In this case, @MrCooper already said he was going to replace the M190 front drive units with M210 front drive units. So whatever FDUs gearing @MrCooper decides to buy... the rear gears will have to match.

If you only drive in 2WD... then doesn't matter. Just don't accidentally put it into 4WD.

Would you say, then, that 5.13 is a good medium for mixed use? If 5.38 is great for offroading but 4.88 is better around town.

Yeah I'd say 5.13 is a good middle ground. If I was to change the gearing on my manual transmission Bronco (currently with 4.70 gears), I'd probably also go with 5.13. For some people, 5.13 may even be the preferred gearing. Right now a lot of manual owners rarely use 6th gear on the interstate, for example. Going with a lower gear ratio (higher number) will allow you to lean into 6th gear more often.

And in many ways @Dusty is right. So just to clarify a bit... 5.38 isn't really "bad" for around town driving. But when accelerating you will just have to shift earlier and more often. If you spend a lot of time driving around town, some people might find that a bit tiresome after awhile. Others are perfectly happy to shift all day long. Likewise... 4.88 isn't "bad" for off-roading. But a lot of off-roaders like to have maximum control at low speeds, and having higher gearing gives you plenty of choices when it comes to gear selection.

It's really more about personal preference and finding a balance that works best for how you use the Bronco than anything else. I really was just pointing out that if you like the way your Bronco performs and shifts today, then 4.88 is the closest match to the 4.46 gearing you currently have on factory tire sizes. (Edit-- If you do the math it's in-between 4.88 and 5.13 gearing, so admittedly we're kinda splitting hairs a bit.)

 

[Aonarch]

http://www.grimmjeeper.com/gears.html

Plug in your OEM gearing and tire size on the left, then experiment with 37s and the different gear ratios on the right.

The best way to do this is look at RPMs across different tire sizes and gearing.

You want to stay close to factory RPM, but remember you are turning heavier tires, so it is ok to have MORE RPM at the same speed than less. You do not want less RPM, that will make your Bronco feel very sluggish.

You absolutely have the have the front and rear gearing match.

37s are very tough on the M190, it does not have the torque capacity to safely handle them. So yes, you really should upgrade to a M210 before going with 37s.

I echo everyone else recommending the Ford Performance tune. It is excellent for the 2.3l and really excellent for the 7MT.

Do it right the first time
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Buy once, cry once, etc

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[userdude]

It's really more about personal preference and finding a balance that works best for how you use the Bronco than anything else. I really was just pointing out that if you like the way your Bronco performs and shifts today, then 4.88 is the closest match to the 4.46 gearing you currently have on factory tire sizes.

Nah, bigger is always better. 11.73's for me! I mean, you don't need all them pesky gears! lol

 

[BlueBronco]

I did consider possibly trading for a BL. But I thought if I "needed" to upgrade to 5:13 gearing anyway, then it wouldn't make much sense.

As you can see, gearing opinions on here are widely varied, but you definitely don't "need" 5:13's to turn 37's. Plenty of real world uses of members running 37's on the 4.7's (myself included on a 4-door) and it truly is a good combo. And I as said, especially so on the lighter 2-door. I wheel fairly regular and prefer rocks over the mud. I also am still on the stock steering rack and unreinforced stock tie rods (gasp!) so don't get sucked into having to spend mucho bucks upgrading those components or your Bronco will explode while off-roading bit.

 

[vrtical]

As you can see, gearing opinions on here are widely varied, but you definitely don't "need" 5:13's to turn 37's. Plenty of real world uses of members running 37's on the 4.7's (myself included on a 4-door) and it truly is a good combo. And I as said, especially so on the lighter 2-door. I wheel fairly regular and prefer rocks over the mud. I also am still on the stock steering rack and unreinforced stock tie rods (gasp!) so don't get sucked into having to spend mucho bucks upgrading those components or your Bronco will explode while off-roading bit.

hell my braptor has factory 4.71s but its a 10 spd.

 

[indio22]

If you want to drive in 4WD they have to match. In this case, @MrCooper already said he was going to replace the M190 front drive units with M210 front drive units. So whatever FDUs gearing @MrCooper decides to buy... the rear gears will have to match.

If you only drive in 2WD... then doesn't matter. Just don't accidentally put it into 4WD.


Yeah I'd say 5.13 is a good middle ground. If I was to change the gearing on my manual transmission Bronco (currently with 4.70 gears), I'd probably also go with 5.13. For some people, 5.13 may even be the preferred gearing. Right now a lot of manual owners rarely use 6th gear on the interstate, for example. Going with a lower gear ratio (higher number) will allow you to lean into 6th gear more often.

And in many ways @Dusty is right. So just to clarify a bit... 5.38 isn't really "bad" for around town driving. But when accelerating you will just have to shift earlier and more often. If you spend a lot of time driving around town, some people might find that a bit tiresome after awhile. Others are perfectly happy to shift all day long. Likewise... 4.88 isn't "bad" for off-roading. But a lot of off-roaders like to have maximum control at low speeds, and having higher gearing gives you plenty of choices when it comes to gear selection.

It's really more about personal preference and finding a balance that works best for how you use the Bronco than anything else. I really was just pointing out that if you like the way your Bronco performs and shifts today, then 4.88 is the closest match to the 4.46 gearing you currently have on factory tire sizes. (Edit-- If you do the math it's in-between 4.88 and 5.13 gearing, so admittedly we're kinda splitting hairs a bit.)

Agreed and especially with the manual transmission only having 6 forward gears (not counting the crawler gear) it's about the balance.

For example, my stock base with 30" tires and 4.46 diffs, made 1st gear feel too short on pavement, while 6th gear was useful. Once I switched to 35" tires, 1st gear felt significantly better on pavement (wasn't having to shift out of it so soon), but I lost a lot of the 6th gear usefulness.

The automatic trans with 10 forward gears (including I recall 3 overdrive gears), can probably handle tire size changes better and with less need to change the diff gears.

 

[Bikeric]

I've been running 37's for over a year now. I do have the 4.70 gears and 7MT. I do not use 6th gear at all because the engine rpm's are too low. I'm just fine off-road with the Crawl gear though, so I don't feel the need to go to 5.13's.
Don't forget that you will need to wire in the front locker as well, and you don't have that Hero switch.
I don't understand the urge to spend thousands on an "upgraded" steering rack right now. I've been wheeling on the "weak" rack and never had any issues in 25,000+ miles.
My order would be 1: Lift, 2: JKS clearance kit, 3: ProCal4 Tune, 4: 37" tires, 5: go wheeling, 6: add a winch, 7: M210 locking diff for the front (4.46 would be cheapest, if it's even available).

 

[BlueBronco]

I don't understand the urge to spend thousands on an "upgraded" steering rack right now. I've been wheeling on the "weak" rack and never had any issues in 25,000+ miles.

x2

 

[MrCooper]

OP, 4.88s should be plenty with FP Tune. The great part about the tune with a manual is the downshift rev matching! It sounds like something small, especially since I've driven manuals for decades, but it really eases the whole experience when you get around traffic.


As cost would be the same,

I've been running 37's for over a year now. I do have the 4.70 gears and 7MT. I do not use 6th gear at all because the engine rpm's are too low. I'm just fine off-road with the Crawl gear though, so I don't feel the need to go to 5.13's.
Don't forget that you will need to wire in the front locker as well, and you don't have that Hero switch.
I don't understand the urge to spend thousands on an "upgraded" steering rack right now. I've been wheeling on the "weak" rack and never had any issues in 25,000+ miles.
My order would be 1: Lift, 2: JKS clearance kit, 3: ProCal4 Tune, 4: 37" tires, 5: go wheeling, 6: add a winch, 7: M210 locking diff for the front (4.46 would be cheapest, if it's even available).

Thanks. I definitely could just wheel and see what is needed and save money. You just read a lot online (I know, I know) about that being a weak point with 37s and figured I could get in front of any potential issues, especially if other work is being done, like the m210. Or if I'm tuning anyway, right?

The m210 IS available with 4:46. The m210 cost is the same across different gearing options available. Sticking with 4:46 would save me from upgrading the rear but it's just a few hundred for the gear and pinion plus labor.

Does anyone know if I can fit other model hero switches? They are available online from Ford. Like fitting a BL or sas switch assembly that I could wire the front locker to?

 

[userdude]

I don't understand the urge to spend thousands on an "upgraded" steering rack right now. I've been wheeling on the "weak" rack and never had any issues in 25,000+ miles.

My order would be 1: Lift, 2: JKS clearance kit, 3: ProCal4 Tune, 4: 37" tires, 5: go wheeling, 6: add a winch, 7: M210 locking diff for the front (4.46 would be cheapest, if it's even available).

I've never needed a winch and have just under 25k and have off roaded many times. Subjective experience isn't the same as designing a build for what you want to do and expect to need while doing it. For me it's working my way to Wolf Caves. For others, perhaps they're afraid of breaking down with a busted rack (legitimately or not).

 

[Bikeric]

I've never needed a winch and have just under 25k and have off roaded many times. Subjective experience isn't the same as designing a build for what you want to do and expect to need while doing it. For me it's working my way to Wolf Caves. For others, perhaps they're afraid of breaking down with a busted rack (legitimately or not).

A winch gives me peace of mind and let's me go closer to the "edge". I've used mine half a dozen times to help others and a couple times to save myself. If an "upgraded" steering rack gives peace of mind to others, than who am I to object?

 

[Squatch]

Does anyone know if I can fit other model hero switches? They are available online from Ford. Like fitting a BL or sas switch assembly that I could wire the front locker too?

They physically fit. The wiring goes through a plug connector and they are just switches, so it's possible.

The wiring is the only tricky part. You may have to get an extra connector in case you mess up on the stock end when adding wires to the front locker.

Also, not sure if they line up in the plug by dash order or a universal order, but the info is on here somewhere. I've lifted mine out for the Mabett USB dash.

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