# 4hi vs 4lo

#### James Morse

##### 1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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What's the difference in ratio between the two? I don't seem to be able to find it anywhere. I was just messing with different gear ratios like for instance going to 4.88 and looking at the miles per hour and RPM in different gears and it occurred to me that maybe with that ratio a doubler would be kind of superfluous or overkill because you already have kind of a doubler with the 4lo but I don't know what the difference in ratio is from four high. Once I know that then I can calculate the RPM per tire size per gear per mph. I think basically what I'm trying to do is keep the engine in the power range at very low speeds.

#### 85_Ranger4x4

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I think like most are 2:7ish to 1.

MIne is 2:1.

#### Josh B

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It's been awhile since I've done much of it but iirc 2 low was lower than 1 hi. I used to put it in 2 lo and idle around in the back pasture

#### ericbphoto

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What's the difference in ratio between the two? I don't seem to be able to find it anywhere. I was just messing with different gear ratios like for instance going to 4.88 and looking at the miles per hour and RPM in different gears and it occurred to me that maybe with that ratio a doubler would be kind of superfluous or overkill because you already have kind of a doubler with the 4lo but I don't know what the difference in ratio is from four high. Once I know that then I can calculate the RPM per tire size per gear per mph. I think basically what I'm trying to do is keep the engine in the power range at very low speeds.
A doubler is normally used for extreme rock crawling. It does not replace the transfer case. It is in addition to the transfer case. So, if you are in low range with your transfer case and shift the doubler into low range, it multiplies your gear ratio. It's not something you would use on the road. So ignore that when trying to work out highway speeds with differentials and tire sizes. Low range and doublers are for low speed operation only.

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#### James Morse

##### 1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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Right, Eric, I understand that doubler is in addition to xfr case not a replacement. I don't plan right now to be doing rock crawling; plans can change, but let's just say it's beyond what I see at least for this truck.
My wording was loose - all I meant was if you have a pretty deep ratio (4.88) and you go into 4x4 Lo, then unless I'm mucking up the math here, you have (in 1st gear) 2.47 x 4.88 reduction or about 12:1 and yes of course it's irrelevant to highway speeds, you wouldn't even be in 4x4 at all on the highway (well - snow maybe - which we don't get any more - side issue). Compared to 3.73 in 1st is like 9:1 so changing the rear end (uh, and front) ratio gives you about 30% increase in reduction. If you had 3.08 (unlikely, but just for discussion), and for some reason put in a doubler (like, you didn't know wtf you were doing), as far as rpm's it would be pretty close to the same as putting in 4.88 with no doubler.

Now I could be resting on some false premises here. I keep reading about this stuff and the way I understand it, the more I can keep my rpm's up, it causes less stress on the drivetrain and less chance of overheating the trans and xfr case and differentials. I haven't looked at the torque/hp curve for the 4.0L engine but if it's like most then at really low rpm there's not lots of either. I don't understand why low rpm causes the overheating but I'm just taking that on faith so correct me if I'm wrong.

Highway speed per gear per rpm per tire size just comes into it when I ask the question, what will 4.88 act like on the road. With the .75 overdrive ratio I think it would be ok. Assume here I would never go over 70 +/- anyway and have no interest in doing so, if I ever hit 80 on the freeway it would be unusual and probably only to stay with the flow of traffic like around Atlanta they drive crazy fast and going 65 can cause an accident. So I do want to ask the question, what will my rpm be at that speed and do I accept that as ok.

One thing that's an unknown to me right now is, if you have a manual trans, you know exactly what your rpm's are because there's no slop in it. I went through all this some time ago in looking at trans for Daytona coupes, where you typically have a 6-speed manual and tons of power (say 460 hp) in a 2400 lb car. Here they normally use 3.73 rear end and I have charts that tell me for the given tire size what's my rpm per gear which tells you the theoretical top speed without burying the tach is like 230mph so, completely different issue, I'm just saying the math is available for manual trans but for auto trans it's not necessarily "locked up", there's the torque converter, etc, so speed in gear isn't necessarily a simple matter of the math and how that all works is beyond me right now. I suspect if the rpm's off-road never get to the point of transmission lock up (meaning, you have the actual ratio of the trans's gears), that probably wreaks havoc with the torque converter. I'd want an additional trans cooler but that doesn't help the xfr case or diff's does it.

So there's a bunch of issues some I understand some I don't. What it comes down to is, when I'm off road (very limited experience) I like to not be tearing around because I'm doing it to a) get to secluded places and b) enjoy the ride, so I like to go along sometimes at a snail pace, or, I'm going slow up a steep road with deep ruts down the middle and a precipitous drop off one side so I'm picking my way real slow. Both up and down so trans braking is nice, don't know if auto is a minus for that, probably, but I was told in general auto is nicer for off road so that's what I got. Not to say I don't sometimes give it some gas on a nice straight stretch, but I try to stay sane about it.

For the street, I imagine a 4.88 could light up the tires (talking stock 31" tires here). You might not want to floor it, it could cause a lot of stress on the axle/springs, I'm just saying, it would no doubt improve acceleration, I see that as a potential side benefit for street use. I don't think you can get a deeper ratio and I don't think I'd want deeper. Summit Racing has the 4.88 ("only 2 left!") and I was tempted to think omg I better order it... a bit premature - they're probably available multiple places but you need that reverse toothed one for the front, I found that too, so I think you can get them and probably can later if/when I go that route.

The other thing is lockers. I read all about the Aussie lockers and they seem like the cat's meow, they're always active, ok for the street, but way better than lsd. The only thing that confused me was they were saying coast around a turn and I think that might have been in the testing after the install because if that was a restriction it would make no sense at all.

So I could see putting in 4.88 ratios and Aussie lockers and that would be streetable and super off-road capable. It would be possible to do that (with 31" tires) and not change anything else on the truck, though when you're that far into it doing a lift might be in the picture because everything would be apart anyway, but, you could do just the ratios/lockers and later on do lift because it seems they are separate things. Even if I don't raise the truck, the ratio and lockers would give me a lot of extra traction so for sand, mud, hill climbing in dirt/rocks, it's a big improvement. Other things come into it - shift kit, torque converter, I mean if everything is apart I'd say do those things. You'd want to consider where (rpm's) and how (firm, soft) it shifts.

From a practical standpoint, even though I have the 2 trucks, I don't want my shop hogged for months nor the truck out of commission for extended periods. I can't put lockers in my lsd rear end anyway. I doubt I can find 4.88 rear end out there (used), probably can't even find 4.56, so it's beyond swapping out parts. How I see it is, find a decent axle, tear it apart "on the bench". Take my time rebuilding it and replacing anything as appropriate besides changing the ratios and lockers. The Dana 35 has to come out too (or find one) and have its ratios/lockers done. Then there's the trans, maybe I do nothing with it, maybe it needs something, are shift points affected, I don't know. These are hard things to do, they are saying you need hydraulic bearing press, so maybe some has to be farmed out. The point is if I can get parts to rebuild then swap them into the truck, it sounds way better than having the truck torn apart, can't move it, shop is monopolized, can't drive it, easy to get discouraged, vs working as time permits without the truck torn apart and not rushing things. Glad now I didn't sell the Mazda.

Do I want, or is it even possible, to go Dana 44. I think the Dana 35 is fine from what I've been told here. Not concerned about the rear 8.8", I think it's rugged. In a rebuild probably want to replace all bearings/seals/whatever as appropriate. Not worried about the 4.0L it's gutsy. Might do the injector coils etc at some point, don't know if it matters, it runs great. Once in a while I just floor it, don't know if that's smart but it's fun and I figure if something's going to break let's have it happen close to home and "it burns the carbon out of it" which is I'm sure total bs but that's what we used to say.

Maybe I want to put disc brakes in the rear, I don't think it's necessary or very helpful, just throwing that in.

I'm having a hard time sleeping lately so I'm up and down in the middle of the night reading about this stuff as much as I can. It's a learning curve. I just feel confident in saying, I can probably do everything I would want to do to the truck to make it awesome and still be out of it for something like half the price of a new Ranger, including the sunk cost of the truck itself. A new Ranger with everything I'd want on it is like 43k then you have the insurance, sales taxes, property taxes, higher registration, etc. And it still wouldn't perform like what I described for upgrades and wouldn't have the soul of a '97. That's the whole reason I got the '97 is I asked questions first and was guided to that gen and, yeah, it's not super rare but I assert that it's hard to find a really clean low (125k) miles Ranger that vintage, that said, like has been noted doing the upgrades I mention wouldn't make it less saleable but moreso, to the right person. Though the chance of me selling it after all that would be like zero. Anyway, one thing that pointed me to the '97 gen is you -can- do things to it and also after having the Mazda and seeing how easy it is to work on compared to most other things (e.g., new Ranger) that also made me think, ok, older Rangers rock, I like them, just, the Mazda doesn't have 4x4 and I found I love off road.

I know I'm talking about some things that are hard to do but I tend to choose stuff that's hard, but do-able. Do you know how hard it is to do miter joints on top of dovetails? It's hard!! But I do it and I do it well, it just takes care and patience and the right tools and methods, so I'm not scared and I like projects where you have tangible results (vs computer programs that I did for decades, fun, but kind of "so what" afterwards). Now I can do what I want and one thing I cannot stand is doing nothing it drives me nuts I have to have a reason to get up in the morning and keep my mind going. I'm used to working with very close tolerances so I get it about backlash and bearing clearance and all that. If I have to farm out some work to somebody I trust (good luck there) I will. I have a good hired wrench available. I think it can happen. Anticipation is a big part of these kinds of things, and the work itself is rewarding, and then after all that you actually have something you can use, what can be cooler than that?

No way to talk about these things briefly is there. Thanks for your help and per usual, poke holes in the tentative plans. I got a list of stuff in front of me now that needs doing on the truck regardless - manual hubs, get the door sticker, check slight fluid drip/leak, so on. But everything works on it, so good starting point for upgrades.

#### PetroleumJunkie412

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Use 4 Hi in high elevation.

4 Lo for low elevation.

Simple as.

#### ericbphoto

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Use 4 Hi in high elevation.

4 Lo for low elevation.

Simple as.
You silly.

#### PetroleumJunkie412

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#### ericbphoto

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Highway speed per gear per rpm per tire size just comes into it when I ask the question, what will 4.88 act like on the road. With the .75 overdrive ratio I think it would be ok. Assume here I would never go over 70 +/- anyway and have no interest in doing so, if I ever hit 80 on the freeway it would be unusual and probably only to stay with the flow of traffic like around Atlanta they drive crazy fast and going 65 can cause an accident. So I do want to ask the question, what will my rpm be at that speed and do I accept that as ok.
Here you go.

The other thing is lockers. I read all about the Aussie lockers and they seem like the cat's meow, they're always active, ok for the street, but way better than lsd. The only thing that confused me was they were saying coast around a turn and I think that might have been in the testing after the install because if that was a restriction it would make no sense at al
The aussie locker and similar lunchbox lockers "lock" when torque is applied to the pinion/ring gear in the differential. That torque spinning the carrier rotates the cross pin and forces the 2 inner halves of the locker apart, engaging the teeth in the chunks of the locker. When you coast, you are removing the torque and the cross pin doesn't push the inner halves of the locker apart. This relaxes everything and some springs in the locker separate the teeth so they disengage and your differential now has "differential.action" again.

So, foot on the gas = rear wheels locked together. In a turn, one must spin faster than the other. This puts torsional stress on the axle shafts.

Foot off the gas and coasting through the turn = locker halves separate and allow differential action. Much better for the axle shafts. Sometimes a ratcheting sound is heard. This is normal as the locker teeth are slipping past each other while coasting around a turn. But some people don't like it.

#### PetroleumJunkie412

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Here you go.

The aussie locker and similar lunchbox lockers "lock" when torque is applied to the pinion/ring gear in the differential. That torque spinning the carrier rotates the cross pin and forces the 2 inner halves of the locker apart, engaging the teeth in the chunks of the locker. When you coast, you are removing the torque and the cross pin doesn't push the inner halves of the locker apart. This relaxes everything and some springs in the locker separate the teeth so they disengage and your differential now has "differential.action" again.

So, foot on the gas = rear wheels locked together. In a turn, one must spin faster than the other. This puts torsional stress on the axle shafts.

Foot off the gas and coasting through the turn = locker halves separate and allow differential action. Much better for the axle shafts. Sometimes a ratcheting sound is heard. This is normal as the locker teeth are slipping past each other while coasting around a turn. But some people don't like it.
I had a lunchbox in my 2011.

Cost me a set of nitto tires.

It was horrible for a street driven truck. Coasting through turns is fine - in theory, until you have to coast through an uphill turn.

Went to a Ford LSD with the mustang track lock or whatever they're called clutches. Works well for a daily driver and on oil and gas lease roads.

If I change again, I'll go to something like a helical gear or torsen. Sort of doubting I will, though.

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#### ericbphoto

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Sometimes you just have to apply power in tight turns. It can't be helped. But most if the time, it's not hard to release the accelerator momentarily. Bug gentle curves, no oroblem. Power through. It mostly only matters at intersections, tight switchback turns and parking lot maneuvers. Is a l7nchbox locker ideal? Nope. But, for the price, they're hard to beat if you need the traction.

#### PetroleumJunkie412

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Sometimes you just have to apply power in tight turns. It can't be helped. But most if the time, it's not hard to release the accelerator momentarily. Bug gentle curves, no oroblem. Power through. It mostly only matters at intersections, tight switchback turns and parking lot maneuvers. Is a l7nchbox locker ideal? Nope. But, for the price, they're hard to beat if you need the traction.
All good points.

All comes down to your usage for your hooptie. Pavement? LSD, Helical, Torsen, Aburn, etc. Consider what you're going to spend on tires vs traction.

Off road? lunchbox, air locker, e locker, spool, welded spiders, etc.

My 2 cents.

#### James Morse

##### 1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
Supporting Member
Yes I checked the TRS chart, that's why I tended to the 4.88, because it's ok for 31" tires but also ok for 32", 33", 34" as to staying in the red part which is where I think I want to be in terms of keeping down the stress/heat on the trans and diffs for off road. Rpms in the chart are approximate as stated in it but I can calculate what they would be when torque converter is locked up i.e. ratios then apply vs torque converter is, ah, slipping. I pretty much abandoned the 35" tires idea, just too many issues with lift/fenders and only gains me an inch ground clearance over 33", if I even go there. TRS (other chart) says I can do 6" lift and 33" tires (-might- get away with 4" but would hate to do it then find out no it doesn't work and I have to do body lift or re-do with bigger lift). I know 31" is slightly larger than oem 265's but guys say they are running the 31" with no big issues. If they rub a little bit when steering is totally cut, normally I can just avoid that (ok, that's a pain) and if it's minor rub and happens, seems like it wouldn't actually break anything, might scar the fender wells a little that's about it, and if it does rub it'd be at low speed, I can't think of an instance where I'm at highway speed and cut the wheels totally, it'd have to be some kind of emergency maneuver. I'd go 265's, in some ways less tread with is better because you have more force psi so in theory more grip (I could be wrong) but there's just so little choice in them. K02, K03, Grabbers, etc, can't find 265's. All I can find is regular not-aggressive like Coopers (which actually might be ok) and no sidewall tread on them; I can get Toyo's in 265's, aggressive and with sidwall tread but I have no idea if they are good. It might be my only choice if I insist on 265's.

According to TRS calculator 4.88 would be more than compensating for the 33" tires (again, holding off any decision there because requires lift). There are other advantages to lift (more suspension travel, I'm assuming) than just fitting 33's to get one inch more clearance than 31's. Also disadvantages - cost, work, and raising c/g, and worse highway handling. While 4.88 might be overkill for 31's, it'd be great for 33's, that's my point, so it leaves the option open. Changing ratios in 2 diff's is a big deal, not something I'd want to do twice.
Admittedly 3k rpm (approximate) at highway speed is revving a lot more than one would be used to. So 4.56 might be better, in some ways but then if you go to 33" you are not in the red ("good") part of the chart.

So, foot on the gas = rear wheels locked together. In a turn, one must spin faster than the other. This puts torsional stress on the axle shafts.

Foot off the gas and coasting through the turn = locker halves separate and allow differential action. Much better for the axle shafts. Sometimes a ratcheting sound is heard. This is normal as the locker teeth are slipping past each other while coasting around a turn. But some people don't like it.
AH. Thanks, I get it. You can end up twisting/deforming the axle shafts, or something else in there, very bad situation. On the freeway, gradual turns, you can't coast around them, but it's ok (noted in above post), rotational difference is tiny.
With Aussies, let's say you're driving on the freeway. All fine; you come to the exit - coast around, if it's sharp and not uphill, usually they aren't; then you come to a stop sign and you have to make a sharp turn and apply power. Wheels are locked, you will drag a wheel (stress the axles), I don't see any way around it. You could stop short of the stop sign, apply power straight, then coast around.... totally impractical and you have people honking at you and you're like "sorry, I have locked diff's". Ridiculous, and probably illegal and/or you'll get picked up for suspected dui. It just raises a bunch of issues that one shouldn't be thinking about because it's enough just staying safe driving and trying to keep a safe margin from the nuts out there.

Which explains the other kind of lockers; I thought (reading the Splash build) "why are we adding an air compressor to the truck, this seems an odd way to do things??" but now I see. I need to read about that kind of lockers so back to Eric's build and more reading. It would be the perfect solution to turn them on only when off road. I assume that kind also require no lsd (?). If that's the case I think open diff on the highway isn't a big deal, heck, millions of vehicles have them.

Other issues with Aussies aside, the ratcheting is ok with me, it tells me they are working. You know that beforehand and you won't think omg what is coming apart now. How about on dirt (making tight turns under power), though, then wouldn't the tires just slide or do you still have the axle stress issue? Even with no lockers you already have the binding issue front/rear and we don't worry about that as long as you're not driving around 4x4 on tar which of course you never do.

I think the end result is Aussies off-road, terrific, Aussies on the street, quite bad. Other kind of lockers (switchable), don't want them working on the street, fine, turn them off. Off road, turn them on, they are just as good as Aussies because locked is locked, right? Sounds much better. Unless there's a downside to them besides that they need air which is another layer of complication but maybe just the price you pay for doing things correctly.

Does the air compressor have a reservoir and/or a place you can hook on a hose in case you want to air your tires? Just wondering, not a determining factor at all.

Getting brain fade, will come back to it later. Man if I was trying to do this alone I'd be lost. Will read about the other kinds of lockers too.

#### ericbphoto

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if it's sharp and not uphill, usually they aren't; then you come to a stop sign and you have to make a sharp turn and apply power. Wheels are locked, you will drag a wheel (stress the axles), I don't see any way around it. You could stop short of the stop sign, apply power straight, then coast around.... totally impractical and you have people honking at you and you're like "sorry, I have locked diff's".
You're overthinking and greatly exaggerating this. It's not THAT serious. Come to a stop sign to make a turn. Foot off brake, use some accelerator to get moving. Let off. Get through most of the turn. Start accelerating again. If people are honking at you, you're making too big a deal out of it. Just drive. After a few weeks, it's a habit you barely think about. If you have to power through a sharp turn, the tires do give a bit. It's ok.

Does the air compressor have a reservoir and/or a place you can hook on a hose in case you want to air your tires? Just wondering, not a determining factor at all.
[/QUOOK.

You can add one. I have a Viair compressor under the hood and a 3 gallon tank where my spare used to be under the bed. Quick connects at both ends of the truck for airing up tires or using air tools. I don't even have air lockers. They're too pricey for me.

Generally, there are trade-offs with everything. Use a lunchbox locker, you can't really turn it on and off at will. But it's cheaper to buy and it will not succumb to air leaks or electrical failure. Cheaper and easier to i stall. Does not require switches, fuses, relays, air compressor, etc. Might add to tire wear a little bit depending on your driving habits. Selectable lockers (AEB, Eaton electric lockers, Ox lockers, etc.) Much more expensive. But, when working properly, you have total control. Just turn it on when you need it. No need to even have it engaged all the time on the trail.

High ration diff gears? In a Dana 35 or Ford 8.8", I would still shy away from 4.88 and higher ratios. These ratios require the pinion diameter to get so small the strength becomes an issue, especially with bigger tires. With 31's and, maybe 33's, if you never do any really hard obstacles on steep terrain, they're probably OK. But with the smaller diameter pinion, there is less tooth engagement. Therefore it is weaker.

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