Topshift 3+1 question
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Joined: Mar 2011
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You cannot just change the OD. TOD has 3 different ratios .71, .72, .& .78 If you have plenty of horsepower a .70 OD works. If the horse power is somewhat low a .70 OD will burn more gas than a .80 OD. As soon as you go beyond a fifth over (.80) you must have excess horse power to compensate for low RPM. If you loose 30% of your engines RPM in OD will you still have enough power to drive without increasing fuel consumption? Example; most GM vehicles in the 80s lacked OD because they were more fuel efficient in direct drive. Low compression ratio and high RPM to develope Hp made OD a bad idea. I was one of those people who did not really believe that until I wasted a lot of hard earned money to put a five speed in my 1980 one ton.
I'm making my absolute final drive ration (right down to the tires) as close as I can to the vehicle the motor will be coming out of. At .70 OD running 205/75 R15 my rear end ratio will need to be at 4.11 which is what I wanted to run anyway. with the .80 OD I'd need something like a 3.80 rear. no big deal, I'd just have to compensate for the OD is all. my truck also weighs the same as most quad4 powered cars so I don't have to worry about that.
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pineconeford
1948 - 1956 F1, F100 & Larger F-Series Trucks
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Sep 16, 2016 08:08 PM
DHCowdude
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Jun 19, 2011 11:03 PM
