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Discussion Starter #1
Looking for some advice on gearing for my 1986 4x4 Ford F-250. I think i have 4:10 gearing according to the axle code of 35 in the door jam. I would like to know how much higher gear ratio i can go to improve my fuel mileage. I dont have an overdrive. Do you have to have the same gears in both differentials? Thanks....Tom.
 

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If you want to use 4x4 you will have to change the front end as well. Then next step down I think is 3.55. It would work great. 14% reduction in rpm's 3,000 would become 2,600.


Another option would be a gear vender, it mounts behind the t-case and is an aux. overdrive. Its like a tiny auto transmission that you can turn on and off manually, or set it for automatic.The guy I bought mine from had it on a '84 he said he would consistantly run 19 mpg. It will drop your rpms by 28%, so 3,000 becomes about 2,200.


Little spnedy new, I got mine used for $1,000. There are other options for aux. trannys, but I don't know much about them.
 

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Hi Tom,


I'm a newbe here too and just bought an 86 also and from what I've dug up so far is these were avail w/4.10's, 3.73's or 3.54's. There is a metal rag attached to one of the cover bolts that has the axle ratio stamped on to it. Mine has the 3.54's and for my use is great. General driving with the occasional dragging another project home. If you are planning any big towing like a trav trailer etc for any length of time or often I wouldn't go any higher(lower numerically) than 3.73's or just stay with the 4.10's if you serious tow.


PS: Is your sig file correct? 6.2? You got a Detroit in there? ;)
 

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Discussion Starter #5
Sorry it took so long to reply but i work a funky schedule. Thanks for the info on the gearing. I think i messed up and put 6.2 in my signature instead of 6.9. I also have a 84 chev with a 6.2 that i was looking for info on. 6.9 has much more power!!!! I love it. I just bought another 1997 F-250 7.3 turbo. It is being shipped from Texas as we speak. Really looking forward to that. Thanks again for the reply and good luck. ....Tom
 

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Tom, if you ever want to get rid of the Chev drop me an email. I'm looking for a donor rig for a 6.2/trans to go into a 72 J-4000 Jeep truck and I'm only about a hour and a half from you.
 
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