Stretched bronco towing thoughts?

[CDavis]

Well the title says it all and I know there’s other posts on this with a whole lot of people freaking out because they’re basing their opinions on factory recommendations. I have a towing vehicle absolutely capable of this but that’s not as fun as taking my bronco out for the weekend and wanting the trailer with me. I’d also like input if anyone knows much about bracing up the frame to handle the weight of a trailer better.

I’m in the middle of my build right now, but in have a pretty good idea of the direction I’m taking this bronco. And there are goods and bad’s for towing with what I’m doing. So let’s lay this out there and see what people think a safe limit would be. To start with, like the title say’s this bronco has been Stretched 27.5” and will be a 4 door in the style of what Krawlers edge did. This bronco is lifted 5.5 with 2” on the body. It currently has 33x12.5 tires but I will be going to 35 or 36. It has 3.50 gears and I bet I will be going to 4.11 when I get bigger tires and I know you probably want me to go more on that but hang on. The transmission is a BB ZF5 not the diesel one. The motor is a 4BT Cummins that I plan on pushing to about 250hp and that should be something like 400ish or more Torque. The front has disk brakes and someday so will the rear along with a likelihood of being upgraded to Dana 60’s. This rig will also have an electric brake controller and will be using a WD hitch. As for the trailer I have a tandem axel wilderness 70’s something and I think it’s something like 3500lbs.

 

[blubuckaroo]

Even re-reading your post, are you asking about flat towing or trailered towing?
It's really difficult to tell.

 

[Jdgephar]

I think the question is about using the Bronco to pull the 3500lb camper

Sent from my SM-G950U using Tapatalk

 

[CDavis]

The camper is the main objective and about the heaviest.

 

[Nothing Special]

I've towed a 2500 lb boat with my Bronco (2.5" suspension lift, 1" body lift, stockish drive train, 4 wheel disks). That's about the limit I'd want to tow with my setup.

Not only is your 3500 lb camper 40% heavier, it also will have a lot more "sail area". Not only a bigger frontal area to push through the wind, but big flat sides to catch side winds. Also the tandem axles will make it want to go straight. Which is a good thing when you want to go straight, but less good when you want to turn.

Offsetting that, you have the longer wheelbase, and if you go with full-width axles that will help too. Really nothing else you list seems to make much difference to me. Yes, more weight will help, but that mostly comes with the wheelbase. And the bigger brakes are great. But the issue I'd be concerned with is stability, and size and weight are what will help there.

Will there be enough to offset the larger trailer? That's in the eye of the beholder. I'm sure you could do it, and you might think it's fine. Personally I think it would be a bigger tail than I'd want wagging that size dog. And I'm pretty sure any cop or insurance company will think it's too big if you get in an accident (whether the trailer was a factor or not).

Which gets to tow ratings. Even though it's very possible to improve a vehicles ABILITY to tow heavier trailers, there's really nothing you can do to increase the RATING. Government agencies and insurance companies aren't going to think that you know better than the manufacturer. Of course a lot of people ignore ratings all the time and not very many of them ever get in trouble for it...

So I can't give you an answer you'll like. I'm sure you can tow that trailer with your Bronco. You might think it tows just fine. But you will be pushing limits in a variety of ways, and even if it does work well it might bite you.

 

[Dirtroadjunkie]

I tow A LOT! Mainly with my superduty. Question you gotta ask yourself is if you can stop your set up heading downhill in the event of a situation.

 

[Broncobowsher]

The funny thing is there is no government rating for towing, it's not placarded anywhere. The owner's manual doesn't state any government regulations. It's pretty much just the manufacturers stating what there product can do and the limits before you overload it (and risk voiding the warranty). Until you get into commercial ratings you can do what you want.

To that, reading the spec list and about the only positive things I see is added wheelbase. Cooling will be an issue, the radiator opening in a Bronco is very limiting. The engine (even the 4BT) puts the fan too close to the radiator. I have dealt with this on other stuff and will just say it hurts cooling. This is where an Explorer dress on a 5.0 with a deep shroud really shines. You are still narrow, going taller, neither is good. Going large on the tires, adding more weight in the Bronco with the parts being put in it (4BT, transmission, stretch) but it sounds like you are keeping 12" disks up front which will be overworked. Even with a trailer brake the truck brakes will be overworked, even without a trailer they will be overworked.
With the 4BT up front a weight distributing hitch is probably a bad idea on a fairly light trailer. The front axle is already heavily loaded from the diesel and even more so with the oversized tires and a weight distributing hitch takes weight off the rear axle and shifts it to the front axle and back into the trailer. I know of a bigger diesel truck that wrecked because it was running a 3000 pound trailer (empty) with a weight distributing hitch and it unloaded the rear axle of the truck. Highway speeds and the torque broke the tires loose and the trailer took it sideways.

The 4BT power curve is odd enough I can't comment on the gearing, but even with the overdrive I don't think 4.11 is enough for as tall of a tire as you want to run. But I don't know the 4BT and its modifications well enough to tell if that is right or now.

Overall I fell it is still a bad idea. Towing is a limit of the weakest link. You addressed one link but are still making so many others very weak.

15 years ago I was going to take a Ranger and make it a tow rig. I had some ambition. It was a 4.0 and I put in a stroked 5.0 thinking the power would be good. Made sure the cooling was good. Built it for a bit of performance but towing as well. It was garbage! I completely overpowered the chassis (and it was only 250 HP at the wheels). No lift, generally pretty stock. What balance it had between strength and power wasn't there anymore. I could tow, but it was less safe than stock. I can just feel that you are building the same thing, only worse.

 

[No Hay]

I tow A LOT! Mainly with my superduty. Question you gotta ask yourself is if you can stop your set up heading downhill in the event of a situation.

Yep, always should be question #1.

I'll bet most early Bronco's can't stop by themselves properly in a true "situation."

 

[hankjr]

Yep, always should be question #1.

I'll bet most early Bronco's can't stop by themselves properly in a true "situation."

and in a worse case scenario, the builder is 100% liable for the modifications that the plaintiffs lawyer will argue are the cause of the accident......

my 1/2 ton can tow my bronco easily enough around here. that does not equate using that same tow rig to tow across the country or over wolf creek pass. in such situations, i want my tow rig to be the bigger part (60-70%) of the equation and not getting pushed around.

stopping power and stability are the key in towing IMHO

Hank

 

[hyghlndr]

Is it worth wrecking, dying or hurting someone else? I wouldn't tow a 3500+ trailer with any Bronco.

 

[56f100bbw]

Hyghindr said it and me no way risk too high

 

[74BroncoCO]

I wouldn't sell your real tow rig until you can test out your setup thoroughly. As others have said, you need some awesome braking and some very careful defensive driving. Your stretch helps a lot. The 4BT is capable, if you can keep it cool. Gear ratio...I would say you probably are in the ballpark. You would need to decide tire size first and perhaps take out a little suspension lift. 35's, you can probably get away with 4.11's. But you might want to see what the numbers look like for 4.56's.

You also need to keep body roll under strict control. You probably need a front sway bar just because of the 4BT. You might consider one in the rear as well.

I'll admit, it is a bit on the sketchy side, but I would bet that the majority of early broncos on the road fall under that category.

My sketchy towing story is dragging my bronco on a tandem axle trailer up to Georgetown, CO for some ice racing in my single cab, short bed '99 F-150. And the trailer had no brakes. I'm betting the load outweighed the tow rig. The real issue was dropping back out of the mountains. That was crazy stressful. But your camper at 3500lbs, that won't be an issue for you.

 

[CDavis]

I wouldn't sell your real tow rig until you can test out your setup thoroughly. As others have said, you need some awesome braking and some very careful defensive driving. Your stretch helps a lot. The 4BT is capable, if you can keep it cool. Gear ratio...I would say you probably are in the ballpark. You would need to decide tire size first and perhaps take out a little suspension lift. 35's, you can probably get away with 4.11's. But you might want to see what the numbers look like for 4.56's.

You also need to keep body roll under strict control. You probably need a front sway bar just because of the 4BT. You might consider one in the rear as well..

I like the idea of the sway bars even if not for towing. As for the gears I know the 4.56 would be a better option. But what I’m looking at is my hwy rpm’s and then I’ll just have to feel it out if I need to drop them more. I’m actually curious how much this Broncos gonna weight when it’s all said and done. With the addition of a full cage rock bumpers and a winch as well as a roof rack. I think normal Broncos come in around 5k. The tow rig I have now is a 97 f-350 crew cab long bed with the 7.3.

 

[Nothing Special]

.... As for the gears I know the 4.56 would be a better option. But what I’m looking at is my hwy rpm’s and then I’ll just have to feel it out if I need to drop them more....

If you find your axle gears don't play well with the overdrive when you're towing you can always just leave the ZF5 in 4th. So then the axle ratio question is more about whether 1st gear will be low enough. And I can't imagine it won't be with 4.10 gears, even with 36" tires. Not saying that 4.10s are a better choice than 4.56 (I don't know which would be better). But people often get more worked up over small changes in gear ratio than is deserved, especially when there are transmission gears to play with.

And I'm not saying that the whole idea is a good one. I said my piece on that above. But I don't see a 4.10 or 4.56 gear ratio being significant in the grand scheme.

 

[CDavis]

Yeah it’s not like I plan on breaking any speed records. Ideally I would like a bit smaller camper with pop out sides. This camper just happens to be what I have.

 

[Apogee]

Yeah it’s not like I plan on breaking any speed records. Ideally I would like a bit smaller camper with pop out sides. This camper just happens to be what I have.

The T@B style of campers (~2000#) would be a much better fit for your tow rig IMO. The 3500# trailer weight is at the limit of what a 4-dr Wrangler (properly spec'd) will tow, but then you're adding lift and tires and everything else to the mix, which certainly isn't helping things.

 

[unimogger]

After having my frame stripped bare, and seeing how flimsy it is especially in the back, I wouldn't want to hang any sort of hitch from it without some reinforcement. And even though your stretched, you don't have full width axles, and you're lifted with no sway bars.
It's a hell of a lot to gamble.
I wouldn't hesitate to drag 3500 pounds behind a 78 bronco, but the early bronco doesn't give me the same confidence.

 

[Broncobowsher]

The T@B style of campers (~2000#) would be a much better fit for your tow rig IMO. The 3500# trailer weight is at the limit of what a 4-dr Wrangler (properly spec'd) will tow, but then you're adding lift and tires and everything else to the mix, which certainly isn't helping things.

I think that is the rating on a stock 4-door wrangler, not derated due to modifications.

 

[CDavis]

After having my frame stripped bare, and seeing how flimsy it is especially in the back, I wouldn't want to hang any sort of hitch from it without some reinforcement. And even though your stretched, you don't have full width axles, and you're lifted with no sway bars.
It's a hell of a lot to gamble.

I agree, I’m hoping somebody has any ideas about bracing it up. Even for lighter towing it’s pretty flimsy.

 

[Digger556]

Read up on the following:

Stability and Control Considerations of Vehicle-Trailer Combination
https://pdfs.semanticscholar.org/4e85/07f1e0f1cfc41dc4cb052ae328336eef1e34.pdf


SAE J2807 - Performance Requirements for Determining Tow-VehicleGross Combination Weight Rating and Trailer Weight Rating
https://www.fordtransitusaforum.com/attachments/j2807-feb2016-pdf.125812/


Also, I can't find a copy, but SAE J684 specifies minimum load specs for trailer hitches. This should give you an idea of how strong your frame needs to be.




Can a Bronco tow 3500 lbs? Absolutely, if built right. Read the first document. Speed and trailer configuration are major factors in trailer stability. To tow above the original factor recommendation, consider:

- Longer wheelbase
- Heavier duty axles
- larger brakes
- hydroboost
- better engine
- more radiator
- trailer brake controller
- wider axles
- proper anti-sway bars
- slowing down


Like many vehicle-related questions, there is never a simple answer. In this case, there is a lot of complicated math just to determine the stability of the system. But then you also have to consider power required, braking, thermal management, safety additions, etc. Jeeps are a good modern vehicle to look at for comparison to a Bronco. If the Jeep isn't rated for what you're doing, there is a good chance you should avoid trying.