ZF5 or E4OD For Big Blue?

As many of you know, we are in New Mexico with Big Blue.  Janey and I drove out on Tue/Wed and our son Bret flew in Wed night.  Then he and I took off up into the mountains and since most of the forest service roads are closed due to the massive snowpack and runoff we hiked.

Bret hasn't driven a manual transmission much but he managed to do fairly well with Big Blue.  However when I asked him on the way back what more needs to be done to the truck to enable us to go more places his first suggestion was an auto tranny.  As it turns out I do have a brand new E4OD in Dad's truck that would bolt right to this 460, and the EEC-V computer would control it nicely.

So that raises the question of how much difference in off-roading that would make.  The ZF5 has a 5.72 first gear while the E4OD has a 2.71.  In fact, the ZF's second gear is 2.94.  But the E4 has a torque converter that multiplies the torque by usually 2.5 according to everything I read, including this Motor Trend article.

Doing some reading about the subject I found this article in Off Road Manual that pointed out what I'd not thought of - driver skill level.  They say "This is a big one. If you’re new to rock crawling, off-roading, or especially driving a stick shift, it’s probably better to go with an automatic, at least for now. If you’re a beginner, stay away from manuals until you know what you’re doing and understand how to control your vehicle off-road."  Bret is not only new to both driving a stick and off-roading, and he doesn't have a chance to learn either until we do it, and that isn't the best time to learn.

Given that, what do y'all think about an auto vs a manual in off-roading?  (I know some of you are thinking "Oh no!  Don't do more work on BB!  Move on to Dad's truck!"  But I'm really asking a technical question about the best tranny for off-roading with an auto-trained driver.  And, since I'm still traveling I won't be able to check in very often, but please don't let that stop you in replying.)

The big key to me would be what your son wants to be comfortable driving it off road.

I can't speak much about off roading but I'd definitely agree that "for the auto-trained driver" learning or proficiency while bouncing over uneven terrain is not in the cards.
I've been driving manual since 6th grade (in fact I've never owned an automatic) so what's second nature to me is never going to be for Bret.
Even then there are situations where I'd prefer an auto, like bumper to bumper traffic or starting on an uneven hill.
All the wreckers and flatbeds I do drive are automatics, and it's certainly simpler.

Also consider how much the E4OD would improve Big Blue's towing capacity (if you intended to work him that way)
I'm sure you have those charts, Gary...  💡

Would it just be a straight across swap?
Do you have a column?  Driveshafts? Do you want to modify the floorpan like you did to Dad's Truck?
Would the Zf-5 S-42 (420 ft lb) be able to handle the torque that 400 is putting out?

Maybe more questions than answers... but if you're asking anything about Bret's comfort and safety off-road I'd say E4OD.

For my money, autos are easier off road - but not so much easier that it's worth the trouble of swapping one, or the loss of the superior performance the rest of the time. Yes, Bret may not be experienced with standard transmissions right now, but he'll learn. Stick it in 1st, 4low, and just let her run.

The gear ratios tend to work out in the favor of the ZF-5 until you factor in the torque converter, which flips it around or at least much closer (~. However - dealing with torque converters has always been a bit more of an exercise in fighting the converter for me than in actually getting somewhere. Clutches give you a very simple control over wheel speed. Put in this much clutch in that gear and your wheels will attempt to reach that speed. A torque converter will sometimes rubber band you around between stalling and spinning, and even when that doesn't happen, they can be tricky to get to do what you want as it's not always a linear relationship.

Also worth noting that the 2.5x multiplier is moreso an "absolute peak torque improvement" number rather than an accurate reflection of what sort of wheel speeds you can get down to - and I've found that traction is usually the limiter off road, not torque.

For my money, keep the stick, drop in some 4.10s or 4.56s and maybe step up a tire size if you want. If it's still not good enough, you can go to the auto then - all the benefits of the gears will transfer - or find a fancy doubler-type box that'll get you a lot more low range. But then - it's not my money, really.

Having had both, not doing rock crawling, but a lot of mud at our 960 acre BSA camp. What I have found is this, Chrysler and GM automatics always would start in 1st gear, even if you wanted to start in 2nd to reduce wheel spin. Ford, when they changed from the old dual range Cruise-O-Matic shift pattern in 1967, kept one of it's most useful features, the ability to start in 2nd gear.

I found that by using 2 on a C6 I could pull a stuck pickup with my 1971 Colony Park wagon, with no wheel spin, but still had plenty of pulling power. I also used it during one of our more significant snow storms with no problems. My first car was a 1964 Falcon, 260 V8 and the Ford fully synchro 3 speed. Second car was a 1966 Shelby GT350, 4 speed. I had a Jaguar E-type coupe, and a 1961 Mercedes-Benz, both 4 speeds. First truck was a 1958 F100, 223 six and 3 speed.

The automatics, can be a "set it and forget it" in mud or snow, and probably rock crawling, manual is good for control in accelerating, decelerating and especially going downhill where control is needed.

Most modern automatics have lock up torque converters, but they unlock when the throttle is closed.

I'll preface this with the fact that I'm not a big fan of automatics, so I'm sure that bias will affect my recommendation.  But I'll try to be fair and I'll give my reasons, so you can decide how much you want to weight what I say.

Dealing only with driving off-road (since that's what you asked), most of what I've read says autos are better off-road, preferred by most of the most capable drivers.  Rock bouncers obviously want the "rubber band" compliance of an auto (if you don't know what rock bouncing is, Google it!).  In mud and in hill climbs the ability to downshift without giving up momentum can be huge.  And I used to work with a guy who did rock crawling similar to me.  He preferred a manual in most cases, but he had an auto in his primary rock crawler.  What sold him was how you could bring an auto to a stop with the brakes, turn the wheels while you were stopped, and then start up again, all without unloading the drivetrain.  When you try to do that with a manual the drivetrain unloads when you push the clutch in and the vehicle moves.  Not necessarily forward or backward, but all of the tires don't stay in the same places.

OK, so that's all theory I've heard.  It makes sense to me, but I have almost no experience 'wheeling automatics, so I can't vouch for it from personal experience.

From my experience (which includes teaching my sons to 'wheel, even though they don't have much experience with a manual) I think a manual trans is easier to drive in the kind of 'wheeling I do.

Going down steep hills is the most obvious place a stick will out-perform an auto.  When you want compression braking the torque converter will hurt the E4OD's already bad low gear of 2.71.  So in comparison to the ZF5's 5.72 the E4OD will be terrible at controlling your speed down a steep hill.  That means that you'll have to use the brakes going down a hill.  That's not the end of the world, but it seems to be easier to lock up, start swinging around and possibly roll.  You can certainly avoid that by gaining experience on less steep (or less slippery) hills, but in my experience (including with my sons), there was a very fast learning curve with a manual (and again, I have no personal experience with an auto here).

Going over big rocks is another place I think a manual is easier to learn, although I don't think the difference is as big here, and I'm sure there are those who will disagree with me.  With a manual you put a tire against the rock, give it enough gas and it climbs smoothly over.  OK, you need to learn how much is "enough gas", so there's a learning curve there.  But the failure modes are usually pretty mild.  If you don't give it enough gas the engine dies.  No big deal, now you're just sitting still.  That usually means just restarting it, backing up a bit and trying again.  Give it a little too much gas and you'll jump up the rock, and probably scare yourself so you let off the gas.  Again, not a big problem.  If you panic and floor it, well then you might break something, but panicing never goes well, and I don't think a manual is at all worse than an auto for this anyway.

With an auto you don't need to worry about stalling the engine (not that stalling is so bad...).  You roll up against the rock slowly and you stop when you hit it.  Now you gently roll into the throttle until you start climbing the rock.  That's all great, but what happens next isn't always.  As you get on top of the rock that rubber band is stretched out and it suddenly releases.  You are well into the throttle, the engine is racing and the truck jumps forward, bashing into the next rock.  Obviously with experience you can learn when to back off the throttle, and how to get on the brake to prevent damage when doing this.  Again the caveat that I've never driven an auto in those conditions, but I find it hard to believe that learning how to avoid the problems of an auto before you damage your truck is easier than learning how to avoid the problems of a manual before damaging the truck.

Hill climbs, as I mentioned briefly, I'll give to the autos.  If you pick the right gear in a manual they are usually fine.  But picking the right gear isn't always easy (especially for a beginner).  And an auto makes this a no-brainer.  Mud is another I'll give to the autos.  Again, changing gears on the fly can stop you dead with a manual while the auto will just keep going.

And yes, you do need to learn how to start on a hill with a clutch.  But with a hand throttle and low crawl gears that's really easy.  Hold the engine speed up a bit with your hand, start letting out the clutch and only start letting off the brake (slowly!) after the engine speed starts to drop.

I will say that screwing up when starting the engine on a hill with a stick can be fatal.  When my sons try to start my Bronco's engine in the driveway they frequently will push in the clutch before hitting the brake.  Since I don't have a parking brake yet, that means the Bronco starts rolling.  Usually not a big deal in my driveway, but on Black Bear Road it would be a whole 'nother matter!  And I wouldn't trust a parking brake on Black Bear anyway, so don't use my lack of a parking brake as a reason to discount this risk.  Either the driver needs to know what order to push the pedals or else he needs a coach to keep him from screwing up when he's in a place where he can't afford a screw-up.

Again, I'll admit that most people do prefer autos off-road.  And someone who's not comfortable with a manual might never overcome that discomfort.  But at least in the situations that I seek out 'wheeling, I found it quite easy to get my younger son comfortable with 'wheeling a stick even though he's not comfortable driving it on the road (he can do it pretty well, and does enjoy the challenge, but he has to think about it too much to be comfortable with it on the road).  My older son is not comfortable 'wheeling my Bronco with a manual.  But he's done it pretty well.  And I don't think he'd be any more comfortable with an auto.  He just isn't comfortable 'wheeling.  And that's OK.  I keep saying it's not for everyone!

So there are my admittedly biased thoughts.  Do with them what you will.

Guys - Thanks for the input. I’m not in a position to respond yet, but I am reading the mail and will respond when I can.

ArdWrknTrk wrote

Even then there are situations where I'd prefer an auto, like bumper to bumper traffic or starting on an uneven hill.

I have no offroading input, but I have to agree that having an auto sure is a lot nicer if you ever have to sit in traffic for any length of time.

I generally like manuals but they can get hairy off road. There have been times where I've had to balance all three pedals and me not being skilled enough to heel-toe even if the pedals were set up for it was not gonna happen. Though having a really slow 1st gear in low range helps a ton so you don't have to mash the throttle.

For fun offroading I much prefer an automatic. Its just less stressful and less physically demanding. Towing and spirited driving, I will go manual all day long. In fact, I am looking for a ZF5 and parts to swap out my C6 right now.

Also, hoping to score a Kingpin D60.

tcbaklash wrote

I generally like manuals but they can get hairy off road. There have been times where I've had to balance all three pedals and me not being skilled enough to heel-toe even if the pedals were set up for it was not gonna happen. Though having a really slow 1st gear in low range helps a ton so you don't have to mash the throttle.

For a vehicle that's only occasionally 'wheeled I could agree with this.  But if a vehicle is being set up for it (as Big Blue is), a hand throttle makes balancing the three pedals really simple.  I know I wasn't able to talk Gary into a hand throttle, but he does have the ability to set the idle speed higher, which might suffice.

I've got a hand throttle on my 72 International Dump Truck. It helps a lot when in steep situations on my land.

Ok guys, I'm home and have read and re-read the comments.  Thanks a bunch!

And having done that as well talked things over with our son, I'm not changing to an auto.  I doubt we'll get to do many more of these trips, and if we do we can make do with what we have.  However, if down the road he moves somewhere like the PNW where he could use the truck then we could swap transmissions.  However, we'd also probably have to add back the emissions equipment I deleted.  

But I do have some thoughts/comments:

Throttle: I do see the need for a hand throttle.  Several times we had uphill starts and I taught Bret to start in 1st with the e-brake set and use the right foot to throttle up.  But a hand throttle would help.

Compression Braking: I watched while in the mountains and I really enjoyed the ability to use the engine to slow down.  That makes a big difference, and in 4Low there is some serious braking.

Cab Floor: Hadn't thought about that, Jim, and don't want to do that.  But glad you thought of it.

Driveshaft: I probably do have the driveshaft as Huck had a 133" (RCLB) just like Dad's truck and Big Blue.  So I should have the driveshaft.

Torque: I doubt the 400 has more torque than the 460.  But I also doubt that I can get more than 420 lb-ft to the ground on the street before wheelspin sets in.

MPG: I'd hate to give up the marginal "economy" we are currently getting with Big Blue, and I know the E4OD will hurt that some.

Spirited Driving: The ZF5 is not for the spirited-of-foot.  It is a truck transmission and you need to shift it slowly or you'll pay the price.  The synchros are notorious for failing if pushed, and in my newly-rebuilt tranny you still have to baby 3rd by pausing in neutral when downshifting.  Which is one of the reasons there's an E4OD in Dad's truck - it'll click off shifts very quickly and that roller 400 will make it GO!

But thanks for all the comments.  It helped me think through it.

Gary, I forget how much detail I've gone into on hand throttles before, but since it's here...

There are two basic types that I'm aware of.  My preference is one that stays where you put it.  So if you open the throttle with the hand throttle it will stay there, not go back to idle when you let go.  There are kits like this one that make it pretty easy to implement.  On my very low-tech Bronco I like being able to use this type as a high idle.  It's also nice as a "crawl cruise control" to give a little faster pace when idling down a trail is a good idea (and it's hard to keep your foot from bouncing around at times like that).

The other type is something like a bicycle hand brake lever pulling a cable.  This will return to idle wwhen you let go of it.  Jeff (who I've 'wheeled with at SMORR in Missouri a couple of times) likes this type because it won't bite you by having your throttle open and racing your engine (or ramming you into a rock or something) when your hand isn't on it to shut it down.

Full disclosure, I've never used that type and I don't think Jeff has ever used what I have, so I think you get used to whatever you have and like it.  But I will say I've never had the kind of problem Jeff is concerned about.

Bob - I wasn't aware of a type that would go back to idle when you let go.  Not sure I like that as it seems like you'd have to hold onto it as you took off instead of setting it to, maybe, 1000 RPM and taking off w/o holding anything.

And I like the TeraFlex one.  Thanks for the link.  When I get to that point I think I'll add it.

By the way, PTO via the computer didn't pan out.  Apparently all that does is turn off the emissions since things like ambulances would be stationary for a long period of time.  I tested it and it didn't raise the RPM at all.

Gary Lewis wrote

....  Not sure I like that as it seems like you'd have to hold onto it as you took off....

You definitely need to keep your hand on that style anytime you expect it to do anything.  That's both the upside and the downside to that style, depending on your preference.  If you think you lean toward the kind that stays where you put it, I certainly won't argue with you!  That's what I like too, I just wanted you to know your options.