Towing in 4th gear on a Honda Civic

[ai4kk]

In the old days, we were always taught to tow in 4th gear, especially if 5th wasn't strong enough, both from an available power standpoint, plus 4th was the best gear since it wasn't a gear, it was a straight 1:1 with everything locked together and transmitting power straight through. The thing is, on my 2003 Honda Civic Hybrid, 4th gear is not a 1:1, but a slight overdrive, maybe 0.927:1; none of the gears are 1:1.

On my Civic towing a small teardrop camper, 5th gear doesn't have the power to overcome wind resistance at 60mph at 2,000 RPM. The engine functions in constant electric assist mode until the battery drains then the speed begins a terminal plunge since the engine alone doesn't have the power to pull the parachute er i mean camper at speed and once the RPMs drop low enough (getting close to 1500 at 45MPH), it doesn't have the power at all. Perhaps streamlining the connection might make enough of a difference to allow 5th-gear cruising, I don't know.....but I can guess I would find myself shifting into 4th every time a mouse in front of me farts.

Would I be damaging anything by spending long periods of time in 4th gear? I'm not worried about the engine RPMs, the car itself is geared so tall that 4th gear has me sitting very comfortably at 3,000 RPM at my preferred towing speed of 60MPH, which is where my old Subaru Outback ran in 5th; I'm more worried about longevity of the transmission (specifically 4th gear) by spending so much time in a gear that perhaps wasn't designed for highway cruising.

I would eventually like to set this combo up as a long-distance fuel-efficient traveling/vacation unit, with an aerodynamic fairing mounted on the truck lid and strapped to the bicycle rack/fender openings/rear door openings, plus a receiver-mounted boattail cargo box for the trailer that would also swing out of the way and serve as a kitchen counter since the kitchen is in the back and with the wheels so far rearward, the trailer is nose-heavy as it is. The car doesn't feel the weight (750 lbs) nearly as much as it does the wind drag on the highway.

[ksa8907]

what trim level is that? i wasn't aware a civic could run 2k rpm at 60. you wont hurt anything running in 4th, but aero mods are your best friend. id do something about the area directly in front of and beneath the leading edge of the trailer. below the tire in your picture.

perhaps more of a cone front on the trailer.

[ai4kk]

The hybrid has a few efficiency mods, including different spoilers and gearing. this is the only hybrid model I know of with a manual trans.

Not sure about the trim level, will take a peek next time I'm out but I think the hybrid is it's own trim level/sub-model.

yeah, definitely looking at what i can do with some foam and glass or maybe some polymetal in that gap.

[Ryland]

How often do you change your transmission fluid, because if it's old or low then I can see it causing problems, otherwise I think you are fine.

What kind of mileage are you getting while towing and why are you trying to go so fast?

[ai4kk]

I just got the car so haven't changed the tranny lube yet, i need to find out how to even do that since it's not an automatic.

60 seems like a reasonable speed for a 2-lane highway with a speed limit of 65. The last trip i made was already 6 hours long and we pulled in at 10PM after getting out of externships at 3, so that seemed to work well. As much as i like taking it slow and easy, i also need to get there at times before exhaustion kicks in.

[jakobnev]

[ai4kk]

I was thinking a little more radical...with the main limit being not hitting the trailer while turning and going over bumps, maybe even use a flexible skirt for the parts closer to the edges

[ksa8907]

that may create an even larger low pressure zone behind the vehicle.

modding the area under your trunk might prove useful, dont forget those terrible wheels on the trailer. maybe just take some coroplast and make softer edges.

[ChazInMT]

For tranny lube, only buy the factory stuff and don't believe anyone who says "Just use motor oil." They don't have to buy you're new tranny when the old one dies due to substituting. I researched this a lot for my own Civic and thats what I came to believe.

[hackish]

Originally Posted by ChazInMT

For tranny lube, only buy the factory stuff and don't believe anyone who says "Just use motor oil." They don't have to buy you're new tranny when the old one dies due to substituting. I researched this a lot for my own Civic and thats what I came to believe.

While I agree with you, the factory oil really is just dyno snot. If you google it up you can probably even find which company was making it for honda. In many of their FSMs they specified it was engine oil. I always used honda MTF on customer cars but a lot of that was for liability. If you do choose to use engine oil you don't want to use synthetic because it's too slippery.

As for your other question, pick your gear according to the driving conditions. If the engine is lugging along in 5th then downshift to 4th but for economy you really do want to try and keep it in the highest gear possible without lugging it too much. Pay attention to the sound and feel of the engine, what feels right generally is.

-Michael