Off road build: gear question West trails

[bamabaja]

Truck purpose: bucket list Western trails trip, Bronk trailered, 351,planned 1” BL 5” SL, AT,. From research understand some opinions for certain trails I won’t be properly equipped with 33s or 35s. Other than county roads necessary to access trails, no highway use. So bought built Dana 44 (Reid, RCV, 4:11, disc) from friend of good CB member and very nice build. At the time my plan was for 4:11 gears on 35” wheels. As I gained more knowledge (read confused) I learned while can run 35s, the rpm “sweet spot” for 4:11s are 33” wheels. In that have not done lift, mounted axle nor built rear axle, where plan Ford 9”, or bought wheels, obviously now is best time to change plan. Appreciate thoughts for my intended use:
- run with 4:11 and 33s
- run with 4:11 and 35s
- change gear and wheels, or
- go BIG or stay home.
Thanks.

 

[Hozr]

I read that everywhere as well. I run 4.11 with 35's ZF 5 speed transmission.

It's perfect. With both the 347 and the 3.9 Not sure why everyone bashes the combo so much.

You can run all your gearing numbers on Grimjeeper to see exactly what your combo will do.

 

[DirtDonk]

We don't bash on "your" combo Hozr. We bash on the same gear/tire size combination in an urban street driven EB with a weaker engine that can't pull overdrive except going downhill in a tailwind. In that situation a 4.11 combo is likely too tall by far with 35's and just barely adequate with 33's even. Especially for a trailered trail rig.

With your ZF's first gear, even a shy little 170 could get going relatively easily. Wouldn't be happy in fifth very often I would imagine, but the first three gears would be pretty cool.
So it might work in some setups, like yours, but there are tons of members that have used 35's and 4.11's and hated driving it anywhere.

For bama's rig, an auto with an overdrive usually also comes with a relatively low first gear and that can be very forgiving on the street. Even a C4 wouldn't be too bad, but would not be as happy going off-road without the lower first gear building up more heat in the trans. The relatively high gearing is just not as much fun on the trails as lower gearing is. This is why expensive lowlowlow gears in transfer cases are so popular.

In his case, it's intended to be a totally trail rig only, that's not going to be driven on the street and will be trailered to the trails. Totally different scenario than most these days.
In that case the usual recommendation from us is certainly still going to be "go low, or go home" as well as "don't fear the gear" that you see a lot.
Why would you build a dedicated trail rig and then hamstring it with too-tall gears for your intended purposes?

In your specific case though bama, we can understand that you just bought a built up diff with new(?) 4.11 gears and all the goodies and would hate to throw money at it if it's not needed. In that case it'd be a shame to have to re-do it, so sure just run it and see if you like it. You can always change later if you feel the need. If your engine is built with low-rpm running in mind, it might actually work out to be a decent gear ratio.

So what about the engine? You said 351, but will it be built, or stock? If stock, you're more likely to enjoy the lower gearing performance of a 4.56 or even 4.88 more. If a stump puller cam and EFI on the other hand, you can get away with much taller gearing and still get some enjoyment out of it.

Why 6" of lift though? I know it's a trail rig, but is it just for ground clearance? Or do you just like the tall look? You can run 35's with just 3" of lift and cut fenders, which is why I ask about going with 6" or so. Maybe some of the trails you're planning are like the Hammers? Depending on where you go, more lift might be an advantage, or it might just make the rig less stable and literally tip into obstacles where a lower rig would just pass it by.
Plenty of Broncos with crushed upper windshield frames and roof edges to attest to that!

With either a 4.5 or 5.5 inch suspension lift, there is also a lot more that will go into your build that you would not usually be needed for just 3.5 inches.
If you're already planning a big bad trail rig and want to go all the way with it, then that's great as long as you know what kind of custom fab work and special items you'll have to add to your list.
But at least you don't have to worry about stability on the street, so that's a bonus in favor of the taller lift.

Bottom line is that gearing depends on what you want to do, and what you'll be happy with. And this is where everybody is different. Hozr's torquey diesel and stroker engines are likely good running setups and pull strong from low to mid range, with the 347 likely having a lot on the top end as well.
If the stroker is also running EFI, then there's just no stopping it and a lot of leeway in gearing choices.
Especially handy if driving on the street is involved as well.

Bama is just going trail riding and probably playing around in his home turf a bit "for testing purposes";D as well.
Three speed auto? Overdrive? Low range transfer case? Like to crawl or like to go fast?
EFI or carbureted? Want it to just idle over everything in it's path?
I personally think you could get away with gearing as low as you dare to go, seeing that it's not going to be driven on the street. But I also still say keep the 4.10's because you already have them. It's easy to match up a rear 9" to them and test different setups later if it's just not working out.
But that's why we bash on other's 3.50 to 4.11 with 35" tire combination a lot. It just depends...

Good luck.

Paul

 

[bamabaja]

Thanks for great comments and suggestions. Nothing set in stone except budget and quality build. At my age this is probably 1 shot deal, and too old for major trail work, so trying to assimilate good info and choose build. I’ve looked at AT vendors from Art Carr to TPI, the later located within easy drive to save shipping. But probably have C4 beefed up locally at good shop. And Paul, I somewhat misspoke on 351 in trail rig. I bought local new build 351 with loupey cam and Holley 4 barrel built for a Mustang for cheap that considered using.
Rather than spending on Sniper and new cam for 351, thinking of 347 or 351 low torque Sniper crate motor. And Blueprint got the 306 Bronco motor. I have a Bronco with a 347 and enjoy it. I can drop Holley 351 in U14 street build and get in trouble. So really have most options available. Local friends say just choose and get done. Probably best advise.

 

[Fireball05]

Hard trails no need for that much suspension lift. Off camber stuff will get mighty dicey.

Cut fenders, 3" lift, 35s and lockers will take you everywhere you want to go.

 

[Broncobowsher]

Kill the lift. 6" of total lift and thinking of 33s? That is insane. 33s will clear great with ZERO lift and just trimmed fenders. Not crazy trimming either, just old school normal flares are all you need. Cut the suspension lift in half. 2½" will give a little extra clearance and not completely jack up steering and driveline angles. 1" body lift is fine for a little extra underhood clearance.

When you say you will be running an AT, will that be a C4?

 

[bamabaja]

Yes on C4 with better bands, reverse, etc, is probably front runner on AT. And again lift suggestion is my poor compilation of other folks recommendations for doing Western trails. I proudly profess being raised in mud and hollars so really don’t know a damn thing, other than reading and watching YouTube, about what is needed for a reasonable rig on Western trails. Now ask me about mud holes, cooking collards with fat back, or making barley sipping whiskey, I’m your Huckleberry!

 

[Broncobowsher]

Trails out west range from mild to wild. What are some of the trails you want to run? That can help narrow down how to build the rig. Hell's Revenge in Moab can be intimidating if you never played on big rocks before but doesn't take much to do it if you can drive. It is amazing how stock of a vehicle can make it. A locker in back is about all that is needed to make it easy.

Being stuck on 4.11s is really a limiting factor. I understand that you have the axle already built that way. But since you are not planning any highway action it is a limiting factor.

For a rear axle, 31 spline and a Detroit locker. That will be a great no fuss rear axle for out west.

Can I suggest a lower set of transfer case gears? Say a set of Tera-Low 3.15s? I don't want to go too low so you can still play in the sand if you want but just a little extra gear to help those 4.11s along.

 

[Apogee]

If you're going automatic, why not look at a 4R70W with the controller of your choice, as that gets you a better transmission even in stock form, overdrive and the ability to run a lockup converter. All of these things could allow you to run much higher (numerically) gears, and still run 75 MPH all day to get from one trail to the next. With that transmission, I'd be looking at 4.56 with 33's, 4.88's for 35's if you have a 351W, or one step lower for a 302 based engine.

At the end of the day, if 33's really are the goal, then I'd consider 0-2.5 inches of SL and a 1" BL for convenience and serviceability. Cut to the fenders to suit. Done. Low CoG and plenty of flex if you choose decent springs, shocks, etc., without the common steering and drivetrain issues associated with larger suspension lifts. Suspension lift only determines ground clearance to the body...tire size determines what you have under your axles. All I know is that I get hung up on the axles more than the body.

What is the plan for the transfer case? Tera Lows would be good, but plan on upgrading the output shaft at the same time. Otherwise an ATLAS 3.0/3.8/4.3 could be a nice addition to the drivetrain equation.

 

[Broncobowsher]

Being trailered and already having a built 4.11 axle I wouldn't even suggest my favorite 4r70w. But if we can get a gear swap, won't need the low transfer case and other options.

 

[Apogee]

Being trailered and already having a built 4.11 axle I wouldn't even suggest my favorite 4r70w. But if we can get a gear swap, won't need the low transfer case and other options.

It just seems like the 4.11's are tripping over a dollar to save a dime. Why compromise the build for a set of gears? I don't get it...spend thousands of dollars to have a compromised finished product to save a few hundred? I feel like I'm missing something important to the story of the OP's build, or rationale behind it.

 

[bknbronco]

i got 1" BL and 5" SL and got plenty of room with 37" tires. If you really want that big of a lift i suggest at least a 37" tire. Also im running 5:38 gears but thats with 3 speed and dana 20.

33's are dinky in todays world. you will love how the 37's look and how much better they perform offroad over a dinky 33.

 

[Broncobowsher]

The more I think about it, that is a weird axle build. All those good parts and what is pretty much a highway gear in it. What differential is in it? With how it is built I couldn't even guess. If you said open I could believe it. I could also believe an ARB.

I am leaning a lot more to having that axle regeared. Being it will be trailered, go low. If you ever want to get on the highway with it later put the 4R70W in it.

Running trails out West you need a sorted rig. It is real easy to be 20 miles from a road that a trailer can come done to load you up.

I'm going to hold off on more advise until I get some trail names tossed out here. We might be picking parts to way overbuild the rig, or way under build it.

 

[rsharpnm]

All this fuss over axle gears seems pretty silly to me If you already have 4.11s in the axles, my suggestion would be to run it, and you can change it later if you don't like it.

I live out west and I have run all the major trail systems in New Mexico, the San Juans in Colorado, Moab and Sand Hollow in Utah, and the Hammers in California. I have wheeled vehicles with 31s to 38s, axle ratios from 3.54 to 5.13 and engines from 171ci to 444ci.

As others have mentioned, people really need to understand your usage and what kind of trails you eyeballing in order to make a good recommendation.

You say no highway use, but how serious are you? It is really convenient to be able to run down a few miles of highway to make it to the trail rather than having to tow to the trail head. Also, I find a rig is much more enjoyable when you can tool around town with it on the weekends. Of course, your tolerance for misery can have a lot to do with what you may find acceptable.

4.11 gears are not nearly as horrible for the trail as people in this thread are making them out to be. Actually, for a non-overdrive transmission and a V8, I think they are a great compromise street/trail gear with 35s. I had a stock, tired 302 backed by an NP435, stock J shift Dana 20, and factory 4.11 gears while running 35s on my old '75 Bronco.
For the street/highway, the gearing wasn't too bad. I had decent enough power and the engine wasn't screaming on the highway. It was pretty comfortable on secondary highways (55-65mph), but wasn't ideal for interstate speeds, but the lack of overdrive was largely the culprit there.
On the trail, the gearing was pretty good. Only the hardest, most technical obstacles left me wanting, but I was able to get through them. My crawl ratio was 64.3:1, which given the 2:1 torque multiplication typically accredited to torque converters, would equate to about a 32:1 crawl ratio with an automatic. I think if I had kept the bronco a bit longer, I probably would have installed a TeraLow 3.15:1, which would have landed me at 86.4:1 and probably been about perfect for the wheeling I was doing with that rig.

Another rig I have, I ran 5.13s with 35s back before it had an overdrive transmission. The 5.13s were nice on the trail and around town, but were miserable on the interstate due to the noise and the horrible fuel economy. I actually got worse mileage on the interstate (~3,600RPM @ 75) than in town. It was liveable for short jaunts on the highway, and I drove it as far as about 225 miles on the interstate, but was definitely not enjoyable. That rig now has 37s and a 5 speed, so it is much happier now.

If you don't want to try the 4.11s first and risk having to change the gears down the road, my suggestion would be 5.13s if it really is a trail rig primarily with little to no highway usage. No one ever said, "I really wish I had higher gears for the trail." Low axle gears also have the benefit of reducing stresses on everything up stream such as your driveshafts. With stock C4 ratios, 5.13s would put you at a 29.5:1 crawl ratio with a J-shift Dana 20. Even this will still be a bit on the high side and you will likely want to to run an aftermarket low gear set for the C4 and/or some lower transfer case gearing. I think ideally you should aim to be in the 40+:1 range. Alternatively, you could run a 2.92 gear set in the C4 with a TeraLow gear set for the Dana 20 with the 4.11s and end up with a crawl ratio of 37.8:1 and much more highway-friendly cruising RPMs. This is much lower than the 5.13s alone, but would cost significantly more.

I think anything in the 4.11 to 5.13 range is appropriate for 35s, and it really depends on where you think you fall on the street vs. trail spectrum as well as your transmission and transfer case gearing.

Additionally, you are talking about running way too much lift. As others have said, I wouldn't run more than 3.5" lift with 35s (No body lift). Your rig will be much more stable and climb better the lower you keep it to the ground, and for the trails out west, that's important!

 

[Broncobowsher]

Don't automaticly add 2:1 for a torque convertor. Yes, a convertor will make more torque, but it requires a heavy throttle application and no vehicle speed to do it. Just what you don't want when crawling (bouncing, fine but not crawling). It also gets you nothing for engine braking. Being up against the convertor is a great way to make a transmission hot. With that in mind a convertor is a great way to cheat a little extra in a pinch but you should not plan to be on it all the time.

Crawling is being able to idle up to a ledge, keep idling and climb it and just keep rolling. As most a little tickle of the throttle, add a few hundred RPM.

When you are geared too high you roll up to a ledge (usually too fast), bump into it and bounce back a little as you come to a stop. A stab of the throttle, engine strains against the convertor as it builds torque. You climb. All of a sudden you are not hard against the ledge, you are fairly deep into the throttle, you launch forward out of control as you back off the throttle. This is not driving in a controlled manor. This is crashing through a trail. The only tool you really have is to apply more throttle and hope it works.

 

[rsharpnm]

Don't automaticly add 2:1 for a torque convertor. Yes, a convertor will make more torque, but it requires a heavy throttle application and no vehicle speed to do it. Just what you don't want when crawling (bouncing, fine but not crawling). It also gets you nothing for engine braking. Being up against the convertor is a great way to make a transmission hot. With that in mind a convertor is a great way to cheat a little extra in a pinch but you should not plan to be on it all the time.

Crawling is being able to idle up to a ledge, keep idling and climb it and just keep rolling. As most a little tickle of the throttle, add a few hundred RPM.

When you are geared too high you roll up to a ledge (usually too fast), bump into it and bounce back a little as you come to a stop. A stab of the throttle, engine strains against the convertor as it builds torque. You climb. All of a sudden you are not hard against the ledge, you are fairly deep into the throttle, you launch forward out of control as you back off the throttle. This is not driving in a controlled manor. This is crashing through a trail. The only tool you really have is to apply more throttle and hope it works.

That is what torque braking is for, and no, your transmission is not going to overheat uncontrollably if you do it. Here is an article that helps explain it: http://www.4x4abc.com/jeep101/footed.html My cousin runs 39.5" Iroks with a crawl ratio of 29.9:1 (E4OD, BW4407, w/4.10s) and does the same trails I do with 125:1 on 37s with a manual transmission. For reference, he has run Pritchett Canyon, Moab Rim, Behind the Rocks, etc. in Moab. He even even towed a busted YJ on 40s out of Cliff Hanger. The caveat here is that he is running a 460, but he has never had any tranny heat issues.

You are correct, not all torque converters have a torque multiplication of 2:1. That is just a rule of thumb. In actuality, torque converter torque multiplication ranges from about 1.5:1 to 2.5:1, but these specs are not always readily available, hence the 2:1 general assumption.

Regardless, the point is that you do not need nearly as deep of a crawl ratio with an automatic transmission, with which I assume you would agree? Automatics inherently will not have the engine braking capabilities of a manual transmission, and if you gear them too low, you will fight issues with driving through your brakes.

 

[Broncobowsher]

Start both engines, put in the lowest gear, which one will have a slower and more controlled crawl? One will have about 4 times the ground speed of the other. Until it hits a ledge where it stops. The other will just idle over it.

automatics crawl really good when you actually give them enough gearing to do so.

 

[rsharpnm]

Start both engines, put in the lowest gear, which one will have a slower and more controlled crawl? One will have about 4 times the ground speed of the other. Until it hits a ledge where it stops. The other will just idle over it.

automatics crawl really good when you actually give them enough gearing to do so.

It was never a question about how fast you go. Speed isn't the real problem past a certain point, torque is. I am a died in the wool manual guy myself, but it is just a fact of life that automatics do not require as much gear reduction as a manual transmission for technical crawling, and that is because of torque converters.

Lets say you have two stock Broncos, one with a C4 and one with the 3 speed manual, both with 4.11s. The manual will have a crawl ratio of 28.9:1 and the automatic will have a crawl ratio of 23.7:1 (assuming J-shift transfer cases). I can guarantee the truck with the C4 will out crawl the 3 speed manual truck.

A buddy of mine had a '97 TJ with the three speed auto and 3.07 axle gears with 33s and ran many of the moderate trails in Moab (Hells Revenge, Metal Masher, Fin 'N' Things, etc) without much problem. He had a crawl ratio of 22.9:1. I would hate to attempt those same trails with a manual transmission with anywhere near as poor of a crawl ratio.

When it comes to technical and extreme trails, crawl ratios of 100+:1 become very necessary with a manual, whereas a crawl ratio of 100 or more is not necessary with an automatic.

Don't misunderstand me, proper gearing with an automatic is important, but it is not nearly as critical as with a manual transmission. I think we have derailed this thread enough at this point, so I will leave it at that.

 

[661buster1963]

I have been reading this thread with great interest. I too will have a 351 running on carb and 35 inch tires (BFG 35 AT which seem to measure around 33.25” real deal height) with NP435. Originally was going to be 33% off-road, but I can see that moving to maybe 5% and mainly just fire roads with a F250 4wd truggy in the works. I have 4.11 and was planning to go to 4.88. Probably going to try the 4.11 to start but if it feels sluggish at all going to go 4.56, or still maybe 4.88 for what is now more a Sunday mall runner

 

[Nothing Special]

I've posted my experience before in similar threads, but I'll put it here too. As always, I'm just saying how I feel about what I have. I'm not saying anyone else will like it or should do it. That's up to you.

I have 4.10 gears with 33" tires, an NV3550 trans (4.01:1 1st gear, 0.78:1 OD) and a stockish rebuilt 302.

On the road I really like this setup. I typically start in 2nd gear (2.32:1) and I can be in 5th gear (OD) cruising city streets at 35 mph. No, it doesn't have a ton of acceleration like that, but I can start in 1st if I need to, and it's a manual trans, so I can shift into whatever gear I want to for cruising or accelerating.

I never had the NV3550 with the Dana 20, but with the stock 3 speed manual and Dana 20 it really wasn't a low enough crawl ratio for what I wanted. I resolved that by going with a 4.3:1 Atlas transfer case. That gives me a pretty nice 70:1 crawl ratio in the rocks, with 40:1 (2nd gear low range) being pretty good for most trails.

And most of my off-road use is on trails out west. As I noted above, I find the 40:1 fine most of the time with 33s, but when "trail running" turns to "rock crawling" it's no where near adequate.