New guy here. Just got an 83 Econoline (150?). 3 on the tree manual. Newer 4.9 V-8 installed in 1999. 3.50 rear axle. First and second gear are pretty short and 3rd is legged out a ways. Runs great till about 55-60mph. But with interstate speeds 75mph out here, it is spinning up way too much and killing mileage. I get about 12.5 driving 60mph and about the same in town. I just got it tuned up and should pick up an to about 13.5 to 14 mpg as it was noticabley rich.
I dont mind having a manual. But need that extra gear for the highway. I seen online that there was a 4 speed manual OD in some of these. I would be good with that and moving it to the floor from the column. How easy/hard are those to find and how much rpm drop could I expect between the two (My current 3rd gear vs the new 4th)?
I have considered instead changing my final drive to roughly 3.00. The local mechanic found a 2.75 I can get for $850 installed. At 6000ft, I fear that much change might have me slipping the clutch a bit to take off. But that v-8 has good torque and may be just fine. Any ideas of the rpm drop I could expect at a given road speed if I went with the 2.75 or the 3.00 axle ratio?
Thoughts on one route over the other? I want to get close to 17-18 highway mpg. At 75mph. I appreciate in advance any advise.
Thank you. If a 4 speed manual turns out to be a tough find. I will consider the 3.00 or even 2.75 axle. Cheapest route likely. I will wait until the local shop throws me options. I want to get at least 3 years of camping out of it. And the occasional road trip. Keep ya posted on actions and outcomes.
My van uses the iron cased, side-shifted unit. The others are aluminum case, one is top shifted, the other is the SROD, using a turret mounted shifter. All are described as weak, but the iron box has that iron box, you see.... One guy here has reported running one behind a 390.... No bang shifts or trying to pull the front wheels on the 1-2 shift there....
You can put a T5 in there too. You will need an adaptor, a WC T5 and a steel bearing retainer. One from a Cobra Mustang will have the lower first gear and strength. A little fiddling, but you'll be happier in the hills and turns due to the better gear spacing:
New guy here. Just got an 83 Econoline (150?). 3 on the tree manual. Newer 4.9 V-8 installed in 1999. 3.50 rear axle. First and second gear are pretty short and 3rd is legged out a ways. Runs great till about 55-60mph. But with interstate speeds 75mph out here, it is spinning up way too much and killing mileage. I get about 12.5 driving 60mph and about the same in town. I just got it tuned up and should pick up an to about 13.5 to 14 mpg as it was noticabley rich.
I dont mind having a manual. But need that extra gear for the highway. I seen online that there was a 4 speed manual OD in some of these. I would be good with that and moving it to the floor from the column. How easy/hard are those to find and how much rpm drop could I expect between the two (My current 3rd gear vs the new 4th)?
I have considered instead changing my final drive to roughly 3.00. The local mechanic found a 2.75 I can get for $850 installed. At 6000ft, I fear that much change might have me slipping the clutch a bit to take off. But that v-8 has good torque and may be just fine. Any ideas of the rpm drop I could expect at a given road speed if I went with the 2.75 or the 3.00 axle ratio?
Thoughts on one route over the other? I want to get close to 17-18 highway mpg. At 75mph. I appreciate in advance any advise.
The 4.9 terminology usually refers to the 300 inch six, but you say V8. The 302 V8 is called the 5.0 liter engine, as used in Mustangs, etc.
If you have the six, changing the axle ratio might be worthwhile, but with the 302, you may go nowhere with that. I bought a new 1978 F100 with the 300 inch six, 4 speed O/D, AND a 2.75 axle. Way undergeared, although it could get over 20 mpg on a slow cruise. The transmission had the weakness of using the idler shaft for the O/D and the bearings died at about 80k miles, from what I recall. I just stopped using overdrive. The vans are way heavier than my old 2WD, short bed pickup.
I had an '86 GMC van with a 305 V8 and the stock 2.73 rear axle, auto trans. It got 13 mpg and was pathetically slow. I changed the axle to a 3.42 when I put in a posi and it ran way better, and still got 13 mpg. In town or on the road. I also had a '73 Ford van with a 302 and it got 13 mpg--I think it was a 3.25 rear axle... In town or on the road. Those older vans with small V8's just never got very good mileage, regardless of axle ratio. I don't think the gearing is going to get you as far as you might think in terms of mileage and the clutch may be an issue with say, a 2.75 rear axle.
My current 2002 E150 van has a 4.6 with a 3.55 axle and 4 speed O/D auto, and can get 17-18 mpg on the road; that is a very good drivetrain combo for the big van. 75 mph will maybe get 16-17 mpg. I don't think you will see that with a 302, which I'm assuming is carbureted. If you are running a carburetor at 6000 feet altitude, that may be your problem right there--it will always run rich.
Depending on how many miles you're gonna drive that van, I would crunch the numbers on the axle or trans swap--you may never break even making this change if you only pick up 1-2 mpg. Asking for 17-18 mpg with an older van like yours at 75 mph is not realistic. Drive slower if you want better mileage.
OP has the 302, which is really a 4.9 but as you indicate, is called the 5.0. I have the 300. In looking up the epa rating of my van, I found the 4 speed OD rated 16/20, the 3 gear 15/17. These are the "new" numbers.
3 mpg gain in the EPA simulations for the six.
The 302 is rated only for an OD automatic, and hits 11/14. Can you move it to 17+ with the manual OD? Keep in mind, the 14 is already OD and lock up torque converter. My guess is you'll move it to 15.
OP has the 302, which is really a 4.9 but as you indicate, is called the 5.0. I have the 300. In looking up the epa rating of my van, I found the 4 speed OD rated 16/20, the 3 gear 15/17. These are the "new" numbers.
3 mpg gain in the EPA simulations for the six.
The 302 is rated only for an OD automatic, and hits 11/14. Can you move it to 17+ with the manual OD? Keep in mind, the 14 is already OD and lock up torque converter. My guess is you'll move it to 15.
I agree with your reasoning here, especially if it is a carbed engine at altitude.
Actually, going 75 mph in a full size van with a carbed 302 would probably result in 13-14 mpg no matter what trans and rear end gear. Hell, I used to have an old LTD II with a 302 and a C4, and I think that car was hard pressed to get more than about 15 mpg on the freeway. To the OP--I don't think it's gonna ever get you a payback to start changing stuff. Get your engine running great, and just slow down a bit. (And I will note that it is almost impossible for me to slow down myself--I usually cruise at 70-80 in any car/truck.)
The 302, in my opinion, is just not a good motor for a big van. With the 4x3 bore/stroke, it needs to rev to make any power. Putting a long gear on it will just make it spend its life lugging and will suck gas.
I remember the 300 inch six in my '78 F100 with the O/D trans (stick) and a 2.75 rear end gear would spin about 1600 rpm at 60 mph. It would get great mileage, but would struggle to climb slight grades that I wasn't even aware were there. If I had to order that truck again, I would have gone with a 3.25 or 3.5 rear end ratio--but I bought it for a 60 mile round trip commute, and the EPA's on that truck were 19 and 28! (old basis numbers from 1978)
After 31 years of owning full size vans or pickups, I honestly believe that the modern 4.6 with the 4R70W is the best mileage combo there ever was for a lightly loaded full size van.
One thing I've found is that tires can make a fairly big difference. What do you have on your van?
My '02 came stock with Michelin LTX M/S's, which are great tires. When I decided to replace them, I went with Firestone A/T tires, in a slightly bigger size--30x9.50x15". They were much heavier than the stockers and seemed to make the van more sluggish, and when I crunched some numbers, they lost me 1.5-2 mpg over the Michelins--adjusting for tire height.
Firestone had a 30-day free return policy (pay only for installation, about $50) and I got another set of the OEM Michelins and took the Firestones back. Mileage returned to what I'd been getting. Those tires were gonna cost me many hundreds of dollars in gas thru their lifespan.
Just a thought that there is stuff other than gearing that you can do. Make sure your alignment is right on, for instance. Or if you wanted to go nuts, you could make a chin spoiler a half inch off the ground, go to tiny mirrors, fair in the rain gutters... Actually the aero stuff is what we need at 75 mph--a big van is like pushing a doggone garage thru the wind.
I've bought gas for big vans for a lot of years, so I've given it thought.
One more thought---reeeeal long gearing with a stick gets kind of sucky because you don't have the torque converter to let the engine move along a bit when you give it a little juice.
George and others,
Plenty of food for thought. My father also mentioned the gear change might not yield the desired results. It is a two-barrell. I just got it tuned and leaned out. Since it is still at the garage, I have not had a chance to re-check mileage. Sounds like the investments I mentioned may be for minimal gain and I need to live with it. That is a lot of weight and squareness I'm trying to move through the air. It just sucks a little that our HW speed limits are 75mph and you better go 80mph to avoid a Camry up your backside.
Switching questions in another direction, how pricey to move to a FI intake or maybe a nice aluminum intake and a small spreadbore 4 barrell carb? If running on the front barrels of a small 4 barrell (say a 450-500cfm) would yield any better low to mid throttle mpg? I'm certain it would give more HP across the bored, but with mild driving habits, any potential mpg gain. FI would be preferable.
Thanks for the warm reception and insight. I am a wannabe gear head who is more of a motorcycle guy, but I have some financial resources, and would like to make this van the best I can and a ride I can cherish to its grave. It is in excellent condition inside and out. Will post pics soon.
Switching questions in another direction, how pricey to move to a FI intake or maybe a nice aluminum intake and a small spreadbore 4 barrell carb? If running on the front barrels of a small 4 barrell (say a 450-500cfm) would yield any better low to mid throttle mpg? I'm certain it would give more HP across the bored, but with mild driving habits, any potential mpg gain. FI would be preferable.
Thanks for the warm reception and insight. I am a wannabe gear head who is more of a motorcycle guy, but I have some financial resources, and would like to make this van the best I can and a ride I can cherish to its grave. It is in excellent condition inside and out. Will post pics soon.
Hey, as an old van guy and old hotrodder, it's good stuff to talk about. As with your other suggested mods, I really don't think you're gonna get a payback on the carb, but you may want to ask on the 302 engine forum (remember to call it a 302 or 5.0). I'm guessing that way more pickup/car guys have played with stuff like manifolds and carbs than us van people.
One feature I recall on my old 300 inch six, a great mileage motor in my '78 Ford pickup, was a ONE barrel carb...
Modern fuel injection blows all the old carbs away in terms of being problem and quirk free.
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Actually the aero stuff is what we need at 75 mph--a big van is like pushing a doggone garage thru the wind.
