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What's better mpg? C-6 w/ GV OD or a ZF5

2K views 2 replies 3 participants last post by  outsidebear 
#1 · (Edited)
Alright, I have seen several threads about what is better, the C-6 or the ZF5? Obviously, this is going to depend on several factors: your gearing, what you intend to use the truck for (towing or daily driver).

Why am I asking?....
I have just recently dove into the idi world, and like all of you, I am in love with the dependability and the easy work. I have the c-6 and I have been looking at all my options for the drivetrain. I am finding the c-6 to be a great affordable tranny; but, I really like the idea of swapping out my c-6 auto for a ZF5 5-speed. I also am willing to look at the option of adding an extra 3 gears w/ a gear vendors overdrive unit.

(GV OD cost ~$3,000)
(ZF 5 speed used ~$500-$1200)

I only use my truck to for an occassional sunday drive (1-2 times week) and when I need the work horse to go haul the boat or some gravel or the m/c toys. I would love to drive a 5 speed when I am pulling a load.

What I am looking for is which of the two would give me the best fuel economy? If you did this swap, any major obstacles you ran into? And feel free to share anything else you think I should consider when comparing the two trannys...

p.s. if you tell me your fuel economy PLEASE SHARE YOUR TRUCK INFO (turbo or N/A, which tranny, your gear ratio, size tires) and I am not comparing just a C-6 and a ZF5! I AM COMPARING A C-6 w/ GVOD AND A ZF5.
 
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#2 · (Edited)
ZF5 speed, 3:55 rear ends, stock tires, ATS turbo, I get right at 18.7 MPG doing 100% highway driving at 65-68MPH. With that gearing my tach shows 1950 RPM at 65MPH in 5th over. Fuel mileage was exactly the same before installing turbo. Towing my 3 horse gooseneck, gooseneck flatbed or gooseneck travel trailer I get anywhere from 10 to 13 depending on the load, etc.
 
#3 ·
1986 F-250 4x4 standard cab c-6 4-speed, 4:10 gears, GV-overdrive, factory size tires. Drove from Tacoma, Washington to Butte, Montana, kept speed at 58 mph, about 1700-1800 rpms (going from memory here) got 21 mpg for the trip. Truck had GV in it when bought it. I really only use the GV as 4th over. I've had US Gear in an '84 Ford diesel. I would choose a US Gear over the GV, but don't think US Gear offering them anymore? About 115,000 miles on the truck. No turbo, factory setup under the hood. 3" stainless exhaust had been installed before I bought it. Nice truck, interior as new, good 'ol 55 mph paint job is peeling some, oh well, it's a truck... Gonna keep this truck forever I'm sure...
 
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