Adding an external overdrive unit to e40d for milage
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From: Ohio
Adding an external overdrive unit to e40d for milage
I had an idea yesterday, don't know if it's any good, but thought it was worth running past the general public to confirm it.
I drive a 2WD 1989 F350 XLT Standard cab dually w/7.3L IDI N/A E40D and a 4.10 dana 80 rear end. I'm not to excited about changing the gear ratio for milage (even though I never haul anything...just like driving a big truck) because I like to have power when in need. Would it be beneficial to add an overdrive unit to a perfectly functioning E40D? What kind of increase (if any) would I gain in highway milage if I kept the unit out of overdrive until I was doing 55MPH in 4th gear on the transmission?
If the previous idea was rubbish, would a ZF5 swap make a noticable difference in highway milage?
Just a thought...
~Jon
I drive a 2WD 1989 F350 XLT Standard cab dually w/7.3L IDI N/A E40D and a 4.10 dana 80 rear end. I'm not to excited about changing the gear ratio for milage (even though I never haul anything...just like driving a big truck) because I like to have power when in need. Would it be beneficial to add an overdrive unit to a perfectly functioning E40D? What kind of increase (if any) would I gain in highway milage if I kept the unit out of overdrive until I was doing 55MPH in 4th gear on the transmission?
If the previous idea was rubbish, would a ZF5 swap make a noticable difference in highway milage?
Just a thought...
~Jon
Last edited by kc8uvu; Nov 18, 2007 at 06:15 AM.
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From: Ohio
*feels stupid*
This just answered my question
Bad news: It averages $2,600 new 
I'd still like to know what kind of milage I'd get out of a zf5 tho
Can't believe I didn't google it first *shame*
~Jon
This just answered my question
Fuel Economy: Besides giving you 8 gears and lots of performance the Gear Vendors Under/Overdrive is the most effective way to improve fuel mileage on vehicles running a 3.73 or higher numerical rear gear (ie 4.10, 4.88). Expect 20% increases during highway cruising with any rear gear in the 4's and 10-15% with a 3.73 with any big block engine gas or diesel. Small block V8 engines (4.6, 5.0, 5.4) do not have the bottom end torque to push the trucks aerodynamics in double overdrive so on the small blocks your factory gear should be good (with the exception of the supercharged small blocks).
I'd still like to know what kind of milage I'd get out of a zf5 tho
Can't believe I didn't google it first *shame*
~Jon
Last edited by kc8uvu; Nov 18, 2007 at 06:38 AM.
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
The zf 5 has less parastatic loses than the E4OD, but the E4OD has a wider overdrive ratio, so swapping to a ZF will actually result in higher RPMs than with the E4OD. Although the E4OD is technically less efficient than a manual transmission, the torque converter has the ability to keep the engine RPMs more consistent during accelleration, so in the end, I think the performance will be the same. But once you are out on the freeway, and the TC is locked up, the E4OD may still have the advantage in MPGs.
GV claims a 20% improvement in MPGs, but don't believe it, if you get a 10% improvement, I think you would be doing good. Considereing the cost compaired to the results, my vote is for a gear swap. My truck has 3.08s (I swaped out the 4.10s), and it moves just fine.
GV claims a 20% improvement in MPGs, but don't believe it, if you get a 10% improvement, I think you would be doing good. Considereing the cost compaired to the results, my vote is for a gear swap. My truck has 3.08s (I swaped out the 4.10s), and it moves just fine.
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From: denver
I put a GV overdrive on my f250 with a zf-5 4.10 rear. I get maybe 1 or 2 more mpg on the highway. The drop in rpms going 75 mph is nice. Things I don't like about the overdrive is that it only works above 20 mph and cuts out below that, so for city or stop and go traffic driving it doesn't work well. The other thing is that for my particular situation, 3rd od is the the same as 4th and 4th od is the same as 5th, so yeah I have 10 "gears" its just that 4 of them are the same. Other than that, I really like it.
I just tried out shell rotella 5w-40 synthetic oil and switched tires that seemed to get me another 1 mpg. The last couple of tanks have been just under 17 w/empty truck and mix of city and highway. The new tires are slightly taller and thinner than the old ones.
I just tried out shell rotella 5w-40 synthetic oil and switched tires that seemed to get me another 1 mpg. The last couple of tanks have been just under 17 w/empty truck and mix of city and highway. The new tires are slightly taller and thinner than the old ones.
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