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MazdaMatt 07-23-2008 01:03 PM

how to drive my cube van
I have a 94 Ford F350 chassis with a 20' (that's big) box on it. I use it for hauling my race car to the track because I can sleep in it and the car is out of the elements.

This thing is HORRIBLE on gas. Not only is it a rolling brick (it has a bubble on the box over the cab, but still). It has a 7.3L non-turbo deisel V8 and a 3-speed transmission that shifts by RPM, not by engine load (so i can cruise at redline in city traffic for some reason). Redline in 3rd gear is about 115km/h.

I learned that I can get about 30-50% improvement by going 90 instead of 115.

How the heck else can i sqeeze mpg out of this thing? I try to only stop once at stop signs and I try to time lights. If i try to coast it slows down SO fast that it isn't worth coasting.

HELP ME! It costs me about 100 dollars in gas to go to a race track, then back to the shop.

dann_04 07-23-2008 01:34 PM

hmmm... it sounds like there are some mechanical limits to your fuel economy there. I would say see about aeromodding it as a cinderblock on wheels isn't a good desing. The slower you go the better. If you let off the pedal it doesn't shift up? If that is the case i would say just go slow and accelerate gently. What kind of fuel economy are you getting out of it currently? Also is your engine tuned well, air filter clean, tires inflated higher than reccomended, a/c off(if equipped), fuel filter not gummed up(sometime a problem on diesels) that's all i can think of at the moment.

MazdaMatt 07-23-2008 01:41 PM

I only drive the van 3 times per year. I chose to do 3 double-headers for my required 6 events so I could save on travel costs. I understand that racing uses gas. I'm here to learn how to use LESS gas while still enjoying life. Can't drive the car there, it would recieve so many infractions if i drove it on pulic roads that the police would just shoot me to save paper.

I was thinking about undertray and side skirts, but that may be hundreds of dollars in sheet alum. Thinking about a narrowing rear (since my door is fold-down, it would attach to the door), but that would have to wait since i don't have much chance to work on the truck. As for mechanical state... its decent, but could be better. Current mileage, i'm not sure. I don't use the AC in the truck, but i'm sure it wouldn't matter with the big deisel.

Letting off the gas does not shift up. I could be going 1mph below the "shift point" for an hour and it will not shift regardless of throttle position. That does mean, however, that i don't have to worry about silly down-shifts.

lovemysan 07-23-2008 01:57 PM

I'm going to guess that you use 60-80% throttle to get to cruising speed. Stay under 50mph. 35mph would be near optimum.

MazdaMatt 07-23-2008 02:03 PM

my next trip would take me 6 hours in my car at "regular" driving pace. Doing 35, i may need to slot in time for a couple birthdays.

Do you think I'm better off doing 90km/h on the freeway, steady-speed? or doing 70km/h on country roads that go through towns where I'll be hitting stopsigns now and then?

dann_04 07-23-2008 02:45 PM

I'd say do 80km/h on the freeway and stay right if at all possible. With a car in the back of that heavy monster inertia is your friend. Adding extra stop and go is the worst you can do. try 85-90 with easy steady acceleration. how are your tires inflated compared to the max allowable psi?

MazdaMatt 07-23-2008 02:58 PM

I believe they are a little under max, but before that trip i will top them up to the max. I wouldn't go higher because trucks are more likely than cars to be stopped and checked for safety stuff, and from what I see in the media, they are thorough in this province.

justpassntime 07-23-2008 03:51 PM

I know this is a lot of work but here it goes anyway.

You could change the top of the van. Chop the top and tapper it towards the back. It could even be so drastic that you would need to raise the roof to get your car in. Kinda like a super size pop up tent trailer. It could even be done with hydraulics like a car carriers upper level. I know it's crazy but I always seem to have extreme ideas. It would be cool no doubt, all the other racers would want one. You could even post your mpg on the side of it. LOL

Put a deflector at the front to help guide the airflow over the blunt nosed front.

Have we talked about Airtabs?

MazdaMatt 07-23-2008 03:59 PM

havn't talked about airtabs because nobody seems to be able to prove their worth in other threads. They seem to be expensive too.

Yeah... i think that sort of structural change is a little more costly than my 1.44/L deisel! If i was a little less sane, it would be worth it. I could shape the whole truck like an aerofoil.

Maybe if I later sold the truck and bought a regular pickup and trailer, i could build up walls/roof on the trailer in that fashion, but that's just extreme.

skyl4rk 07-23-2008 05:26 PM

How much traffic is there on the streets you will be driving on?

Can you put the vehicle in neutral while rolling?

Do you have the ability to shift at all? What does your shifter look like: P - R - N - D - 2 - L ?

trikkonceptz 07-23-2008 06:27 PM

Can you post a picture of the vehicle, it could help us help you ..

bhazard 07-23-2008 06:32 PM

a 94 should have an OD trans...

lovemysan 07-23-2008 06:46 PM


Originally Posted by bhazard (Post 46997)
a 94 should have an OD trans...

I was thinking the same thing. But depending on the axle ratio it could still only top out at 65-70mph. I drove a f450 that was geared similarly. You could sell that van and buy a bread van with a 4 cylinder cummins 4 bt diesel. I'm told they get around 18-19 mpg at 55mph. Thats top speed at 2600rpms I believe.

Personally I'd try to save the easiest portion of possible savings and spend the rest of my time trying to move more product. You could also do a little freight hauling. There's a website where people give and receive bids for shipping items like water heaters, mowers etc. You could haul a little extra stuff and make up some fuel cost.

found it!!!
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lovemysan 07-23-2008 07:25 PM

For some strange reason I thought you used the van to do some type of sales at an event. Someday I'll learn to read. I don't think a bread van will hold a car.

Tony Raine 07-23-2008 10:25 PM

ok, this is pretty extreme, but......

cut down the box (especially the bubble top) to a more aerodynamic camper and parts/tools stash only. then haul the car in a smaller enclosed trailer (just enough for the car). aeromod the truck and trailer as a unit.

MazdaMatt 07-24-2008 08:24 AM

Okay, lets just reality check for a second here... I drive this truck to 3 events per year. A 2-hour trip, a 4-hour trip and 6-hour trip. I won't be doing any extreme modifications and the purchase of an extra trailer is a lot more than the entire gas expense of these trips. I'm just looking for some driving tech. This thing is BIG... doing mods to it would cost thousands of dollars.

The tranny is a 3-speed because it used to be a Hostess delivery truck. It was never meant for highways use. This thing handles GREAT in the city, even with 3000 pounds in the back. I am sorry, but I don't recall what the tree says... i think you're right, PRND2L, what could I do with that to help me?

As for coasting in N, that sounds scary to me with a 6000 pound weight rolling down the road... it isn't a metro.

Making up some money with some work on the side would be great, however this truck is insured as a "personal" vehicle so my rates are very low compared to a mover's. If it was discovered that I was hauling something other than my race car (condition of the insurance) I'd lose my coverage. Also, replacing the vehicle is a no-go because it has already been set up with a fold-down ramp door and die-downs for my car.

I'll try to get a pic posted. Its a big ugly beast.

Tony Raine 07-24-2008 09:23 AM

yeah, i figured my idea would not be feasible. but hey, someone had to throw it out there, right? :thumbup:

sounds like you already found your #1 way to save gas (slowing down).

hey, if you win more $$ at the races, you can use that to "save" on gas :D

MazdaMatt 07-24-2008 09:30 AM

Haha... these races have prize pools of synthetic oil, tires and safety gear. I'm not a pro racer.

I think i basically just have to stick to the highway and drive as slow as i can while remaining awake and not disrupting traffic. I'll get my air filter checked out. I'll also see if i can do ANYTHING for the airflow around the bottom and back of the truck.

trikkonceptz 07-24-2008 09:32 AM

Neutral coasting shouldn't scare you. We are not asking you to drive down mountains in neutral, your tranny does little to brake your vehicle unless the vehicle has some type of exhaust braking system. If you drive on level ground coasting to lights you should see a benefit in the tank, hopefully you shut it off when at a complete stop.

Also large trucks like yours should have proper tires for the load you are carrying, therefore inflating them to the sidewall max should also be a non issue especially since ride quality goes out the door. PLus it should extend the life of your tires by not bulging the sidewalls and reducing heat from friction. Those 2 alone should be enough for a mild bump in your beast.

On the aeromod side I don't know if side skirting the truck will be a benefit, but instead of using aluminum paneling which is expensive, consider Choroplast sheets, which are lighter, cheaper and can be braced with aluminum rods to the chassis for additional strength.

Once you get pics up I'll throw some more ideas at you ..

MazdaMatt 07-24-2008 09:38 AM

Ride quality was MUCH improved when I bumped up the tire pressure, actually. The biggest improvement was steering feedback and not acting quite as much like a sailboat. Yes, i gained some FE when i bumped upt he tires as well. I did not, however, put them to sidewall max, so i will do that next time I have my hands on the truck. This thing rides so smooth it doesn't need cupholders. You just put your coffee on the dash.

Simply dropping throttle brings the revs down to idle and allows the truck to coast. I would fear for the health of the tranny if i kept popping it from N to D.

In the drive from the shop to the highway I only see 2 lights, and from the highway to the track it will just be stop signs, so unfortunately i won't see any benefits from turning the engine off. Don't these big deisels idle on fumes (figuratively) anyway?

Is a MPG read-out possible on this thing? Anybody know the 1994 7.3L Ford engine?

Miller88 07-24-2008 10:17 AM

Diesels use less to idle than a gas engine.

I don't a vehicle that old would be able to do a mpg readout with a computer. You can keep track of it manually.

I've done a bit of towing and hauling with pickup trucks. It is my understanding that the more load you have, the higher you put the tire pressures (better for the tires).

... and I thought the only vehicles that had 3 speed transmissions in 1994 were YJ wranglers.

MazdaMatt 07-24-2008 10:22 AM

What about changing my final drive gear so my shifts happen at high speeds and my highway cruise is at a lower RPM? What would that cost me? Does this change happen in the diff or the tranny?

Miller88 07-24-2008 10:26 AM

Since it is a mechanical transmission (sounds it), you shouldn't have a problem with the truck's coputer getting mad. What rear axle does it have and what is the gear ratio? I believe the highest I've seen on those trucks is 3.73.

Have you thought about swapping in a 4 speed OD transmission?

MazdaMatt 07-24-2008 10:41 AM

No idea what rear axle is has. Unfortunately i don't know much about this truck. I've owned it less than a year and driven it only a half dozen times.

I would LOOOOOVE a 4-speed od tranny. Actually, i'd prefer a 5spd manual, but that just isn't going to happen. What would it cost me to swap a tranny in that beast? I have access to a truck shop and some very helpful mechanics in the family, but I can't be sinking a lot of money into this truck just to save some gas.

trikkonceptz 07-24-2008 10:50 AM

If you like you can PM me with your VIN # and I will have my parts counter look up the vehicles info including the rear end gear ratio if you like.

Swapping gear isn't the cheapest thing to do, but it may be a good long term investment.

MazdaMatt 07-24-2008 11:11 AM

I would guess that I will spend a total of 300 dollars fueling this truck this year. If the swap costs me more than 50 OR saves me less than 25, its a no-go.

elhigh 07-24-2008 12:05 PM

It'll cost more than 50. But you've got to amortize that savings - how long do you intend to keep the truck? If you keep it for years and years and it saves you money every year, then you may come out ahead.

MazdaMatt 07-24-2008 12:39 PM

I think i'm pretty much destined to drive slow and give myself an extra hour of travel time. Nearest thing to a mod I could do is a partial narrowing at the back, but even that is looking at 4 sheets of coroplast at 20 bucks each. A skirt for the box would be 4 sheets and an underbelly covering would be another 4 sheets. Not worth it for a seldom-used vehicle, even if it IS a pig on gas. A new 4OD might up the resale, however. 3spd is REALLY stupid. I wonder if i could make a manual shift mechanism for it so i select my gear with a lever or buttons.

wagonman76 07-24-2008 01:06 PM

Another thought. Since you only drive the van 3 times a year, how about selling it and buying/making a trailer for your racecar? You could start with a junked travel trailer and go from there to do it for cheap.

Then for the 3 times a year you need to go to the track, just rent or borrow a basic truck or van to pull it. Youd probably save more than your yearly fuel bill in the plates and insurance you wont need to keep up on the van. Dont know how your area works, so youd have to do the math to see if its worth it.

MazdaMatt 07-24-2008 01:12 PM

Its a close call, i suppose. I don't pay much for licence and insurance for this thing. I suppose i also underestimated my usage. I realize that going to 3 events per year doesn't mean 3 trips per year. I also went to two racing schools in the spring and I'll be going to an open-lapping day in two weeks. I also used it to move last year and I am using it to move again in a few months... the moves are short trips, though.

In retrospect, it gets about 2x the usage I described.

One MAAAJOR reason why i like this cube van for hauling my car is that when i arrive at the track at midnight the night before in the pouring rain or fall cold, I just have to hop in the back where my bed is made up and me and the car can sleep comfortably together out of the elements. My car has no windows, so keeping it inside is a plus.

meemooer 07-25-2008 01:15 AM

Belly pan and side skirts would work well. And i'm thinking it has the good ol' reliable C6 trans. and probably a Sterling or Dana rear axle. You should be able to find an AOD trans for it and it would be a bolt in, then just have to figure out the computer portion which can be a simple control box.
as a side note, your trans doesn't sound right. i think the C3 trans way back in the early 60's was RPM shift sensitive. A c4/c6 should be from load. You might have some problems inside of it, like the valve body is gummed up.

MazdaMatt 07-25-2008 09:26 AM

Thanks for the advice. Maybe next spring I'll take this thing to a truck shop for a total overhaul. This year's budget is pretty dry and it does still drive, i just need to go slow. I'll try to source a rebuilt or junkyard 4OD over the winter, and at that time, maybe pre-calculate my gearing for optimum highway travel.

skyl4rk 07-25-2008 04:02 PM

Your best fuel efficiency will be found at the slowest speed you can go and still have your transmission in the highest gear. There might be some additional gains to coasting down hills and general pulse and glide type driving, however I can understand your concern for the transmission, I probably would not do it with an automatic either.

Clev 12-28-2008 10:55 PM


Originally Posted by MazdaMatt (Post 46828)
I have a 94 Ford F350 chassis with a 20' (that's big) box on it. I use it for hauling my race car to the track because I can sleep in it and the car is out of the elements.

This thing is HORRIBLE on gas. Not only is it a rolling brick (it has a bubble on the box over the cab, but still). It has a 7.3L non-turbo deisel V8 and a 3-speed transmission that shifts by RPM, not by engine load (so i can cruise at redline in city traffic for some reason). Redline in 3rd gear is about 115km/h.

I learned that I can get about 30-50% improvement by going 90 instead of 115.

How the heck else can i sqeeze mpg out of this thing? I try to only stop once at stop signs and I try to time lights. If i try to coast it slows down SO fast that it isn't worth coasting.

HELP ME! It costs me about 100 dollars in gas to go to a race track, then back to the shop.

I just found this thread because it was mentioned elsewhere. You may want to go on the Ford truck forums and see if somebody knows what's wrong with your transmission. It could be as simple as a cable or wire that's disconnected. I've never heard of an auto from the factory that doesn't shift until redline. That would make a huge difference in both economy and engine life.

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